TEDS Data Dictionary

Variables in the 4 Year Dataset

The table on this page lists all 4 Year variables. This includes all item variables from the 4 Year booklets, as well as derived variables that are based on 4 Year items.

The table does not include background variables that originate from other sources (either from admin data or from other study datasets). Such variables include IDs, twin sex and zygosity variables, the random variable and general exclusion variables. See the background variables page for details.

Variables are listed in alphabetical order in the table below. The columns of the table are:

Dataset variable name
Dataset variable label (in SPSS)
Source of data:
- child - from the child booklet
- parent - from the parent booklet
Item or derived variable? - see item coding for the parent and child booklets (pdfs) for item variables; see also the description of derived variables for more information.
Data type:
- integer - numeric whole numbers
- decimal - numeric with fractional values
Variable type:
- nominal - categorical, with arbitrary numeric values
- ordinal - categorical, with ordered numeric values (test items used as scores are treated as being ordinal even if they have a simple 0/1 coding)
- quantitative - numerical measurements of some concrete quantity such as length or time
- scale value - numerical measurement derived (usually) as a sum or mean of other variables
Coding or range of values - this shows the value coding used for nominal/ordinal variables, or an approximate range of values for quantitative and scale variables.

dataset variable name	dataset variable label	source of data	item or derived variable?	data type	variable level	coding or approximate range of values
dac011/2	Active child item 1: playing house (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac021/2	Active child item 2: playing with girls (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac031/2	Active child item 3: pretends female character (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac041/2	Active child item 4: plays male job (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac051/2	Active child item 5: fighting (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac061/2	Active child item 6: pretends family character (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac071/2	Active child item 7: sports/ball games (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac081/2	Active child item 8: climbing (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac091/2	Active child item 9: playing at baby care (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac101/2	Active child item 10: interest in cars (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac111/2	Active child item 11: dressing in girlish clothes (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac121/2	Active child item 12: guns (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac131/2	Active child item 13: jewellery (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac141/2	Active child item 14: tool set (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac151/2	Active child item 15: dolls (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac161/2	Active child item 16: trains (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac171/2	Active child item 17: swords (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac181/2	Active child item 18: tea set (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac191/2	Active child item 19: explore new surroundings (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac201/2	Active child item 20: rough play (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac211/2	Active child item 21: interest in snakes (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac221/2	Active child item 22: avoids dirt (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac231/2	Active child item 23: likes pretty things (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dac241/2	Active child item 24: avoids risks (4 Year), see value labels	child	item	integer	ordinal	1=never, 2=hardly even, 3=sometimes, 4=often, 5=very often
dadparc1/2	Parent-administered Parca total score (4 Year), 0-1	child	derived	decimal	scale	0 to 1
dadparn1/2	Parent-administered Parca mean score (4 Year), standardised	child	derived	decimal	scale	approx. -3 to +3 (standardised)
dagemdex	Exclude on moderate twin age rules (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dagestex	Exclude on strict twin age rules (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dalg2zy	Zygosity derived from questionnaire only (4 Year), see value labels	parent	derived	integer	nominal	1=MZ, 2=DZ, 5=indeterminate, 99=inconsistent data
dalgzyg	Zygosity derived from questionnaire and twin sexes (4 Year), see value labels	parent	derived	integer	nominal	1=MZ, 2=DZ, 5=indeterminate, 99=inconsistent data
dallerg1/2	Health item 16: persistent allergy (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dallergy1/2	Health item 16 type of allergy (4 Year), see value labels	parent	item	integer	nominal	1=nuts, 2=dairy, 3=other food, 4=antibiotic, 5=animals/fur, 6=detergents/chemicals, 7=hay fever/pollen, 9=other
danx021/2	Behaviour item 49: slow to warm to strangers (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx041/2	Behaviour item 16: checks things are done right (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx051/2	Behaviour item 58: asks for reassurance (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx061/2	Behaviour item 4: does things over and over (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx071/2	Behaviour item 44: shy or timid (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx091/2	Behaviour item 25: twitches or mannerisms (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx141/2	Behaviour item 33: fussy (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx161/2	Behaviour item 37: upset when parent leaves (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx201/2	Behaviour item 8: resists sleeping alone (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx211/2	Behaviour item 23: fussy about keeping clean (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx221/2	Behaviour item 41: afraid of everyday things (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx231/2	Behaviour item 53: independent/confident (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
danx23r1/2	Reversed version of behaviour item 53 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
danxfeart1/2	ARBQ fear subscale (4 Year), 0-6	child	derived	decimal	scale	0 to 6
danxnafft1/2	ARBQ negative affect subscale (4 Year), 0-4	child	derived	decimal	scale	0 to 4
danxncogt1/2	ARBQ negative cognition subscale (4 Year), 0-4	child	derived	decimal	scale	0 to 4
danxocbt1/2	ARBQ obsessive-compulsive behaviour subscale (4 Year), 0-8	child	derived	decimal	scale	0 to 8
danxshyt1/2	ARBQ Shyness (social anxiety) subscale (4 Year), 0-6	child	derived	decimal	scale	0 to 6
danxt1/2	ARBQ overall total anxiety scale (4 Year), 0-36	child	derived	decimal	scale	0 to 36
dapalon1/2	Twins apart: respondent alone with twin (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don’t know
dapbed	Twins apart: different bed times (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don’t know
dapoth1/2	Twins apart: others alone with twin (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don’t know
dapother	Twins apart: other reason (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don’t know
daptothh	Twins apart: number of hours per week (4 Year), see value labels	parent	item	integer	ordinal	1=1 hour, 2=2 hours, 3=3 hours, 4=4 hours, 5=5-6 hours, 6=7-10 hours, 8=over 10 hours
dapwake	Twins apart: wake at different times (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don’t know
dasthma1/2	Health item 15: prescribed asthma medicine (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacmen1/2	Health item 20: bacterial meningitis (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacmh1/2	Health item 20d: bacterial meningitis: haemophilus (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacmm1/2	Health item 20a: bacterial meningitis: meningococcal (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacmo1/2	Health item 20e: bacterial meningitis: other (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacmp1/2	Health item 20b: bacterial meningitis: pneumococcal (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbacms1/2	Health item 20c: bacterial meningitis: group B streptococcus (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dbedfrnd	How often twins are put to bed by friends (4 Year), see value labels	parent	item	integer	ordinal	3=often/daily, 2=frequently/weekly, 1=occasionally/monthly, 0=never
dbedopar	How often twins are put to bed by other parent (4 Year), see value labels	parent	item	integer	ordinal	3=often/daily, 2=frequently/weekly, 1=occasionally/monthly, 0=never
dbedorel	How often twins are put to bed by relatives (4 Year), see value labels	parent	item	integer	ordinal	3=often/daily, 2=frequently/weekly, 1=occasionally/monthly, 0=never
dbedoth	How often twins are put to bed by others (4 Year), see value labels	parent	item	integer	ordinal	3=often/daily, 2=frequently/weekly, 1=occasionally/monthly, 0=never
dbedprof	How often twins are put to bed by carers (4 Year), see value labels	parent	item	integer	ordinal	3=often/daily, 2=frequently/weekly, 1=occasionally/monthly, 0=never
dbedrmsh	Do twins share a room with anyone else (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes with each other, 2=yes with each other and someone else, 3=yes with someone else
dbedsh1/2	Twin shares bed (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dbeh011/2	Behaviour item 1: fair in games (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh051/2	Behaviour item 7: destroys belongings (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh061/2	Behaviour item 9: affectionate to family (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh121/2	Behaviour item 21: irritable (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh161/2	Behaviour item 26: bites nails/fingers (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh241/2	Behaviour item 36: wets or soils self (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh261/2	Behaviour item 38: stutter or stammer (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh271/2	Behaviour item 39: other speech difficulty (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh281/2	Behaviour item 40: plays imaginatively (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh301/2	Behaviour item 42: inattentive (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh331/2	Behaviour item 45: cries easily (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh341/2	Behaviour item 46: forceful/determined (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh351/2	Behaviour item 47: blames others (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh371/2	Behaviour item 51: gives up easily (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh381/2	Behaviour item 52: inconsiderate (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh401/2	Behaviour item 54: kicks/bites other children (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh411/2	Behaviour item 55: kind to animals (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh421/2	Behaviour item 56: stares blankly (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbeh431/2	Behaviour item 57: tries to stop fights (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dbpamus	Being a parent item 3: amused, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpamus1/2	Being a parent item 3: amused, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpamusd	Being a parent item 3: amused, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbpangr	Being a parent item 5: angry, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpangr1/2	Being a parent item 5: angry, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpangrd	Being a parent item 5: angry, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbpaway	Being a parent item 4: wish away, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpaway1/2	Being a parent item 4: wish away, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpawayd	Being a parent item 4: wish away, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbpclos	Being a parent item 6: feel close, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpclos1/2	Being a parent item 6: feel close, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpclosd	Being a parent item 6: feel close, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbpfrus	Being a parent item 7: frustrated, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpfrus1/2	Being a parent item 7: frustrated, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpfrusd	Being a parent item 7: frustrated, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbphapp	Being a parent item 2: happy relationship, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbphapp1/2	Being a parent item 2: happy relationship, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbphappd	Being a parent item 2: happy relationship, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dbpimpa	Being a parent item 1: impatient, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dbpimpa1/2	Being a parent item 1: impatient, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dbpimpad	Being a parent item 1: impatient, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dcbmi1/2	Twin BMI (4 Year), kilograms per square metre	child	derived	decimal	quantitative	approx. 10 to 30 (kilograms per square metre)
dcd011/2	Diet item 1: finish dinner (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd021/2	Diet item 2: eat everything on plate (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd031/2	Diet item 3: eat only at mealtimes (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd041/2	Diet item 4: has to be encouraged (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd051/2	Diet item 5: told off for playing (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd061/2	Diet item 6: ensure eats enough (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dcd071/2	Diet item 7: OK to snack (4 Year), see value labels	child	item	integer	ordinal	1=disagree, 2=slightly disagree, 3=do not agree or disagree, 4=slightly agree, 5=agree
dchatot	Chaos overall scale (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dchtcm1/2	Child height (4 Year), centimetres	child	item	integer	quantitative	approx. 85 to 120(centimetres)
dcont1/2	Overall (SDQ and Behar) Conduct scale (4 Year), 0-20	child	derived	decimal	scale	0 to 20
dcwtkg1/2	Child weight (4 Year), kilograms	child	item	decimal	quantitative	approx. 10 to 25 (kilograms)
ddiaoth	Health item 25c: mother diabetes at other time (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddiapro	Health item 25b: mother diabetes while pregnant with other (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddiaprtw	Health item 25a: mother diabetes while pregnant with twins (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddiasko	Discipline item 6: ask someone else, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddiasko1/2	Discipline item 6: ask someone else, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddiaskod	Discipline item 6: ask someone else, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddiblam	Discipline item 7b: which twin blamed more by you (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddiblamp	Discipline item 7b: which twin blamed more by partner (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddicrit	Discipline item 7c: which twin criticised more by you (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddicritp	Discipline item 7c: which twin criticised more by partner (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddiexpl	Discipline item 3: explain or reason, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddiexpl1/2	Discipline item 3: explain or reason, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddiexpld	Discipline item 3: explain or reason, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddifirm	Discipline item 4: firm and calm, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddifirm1/2	Discipline item 4: firm and calm, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddifirmd	Discipline item 4: firm and calm, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddijoke	Discipline item 5: make a joke, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddijoke1/2	Discipline item 5: make a joke, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddijoked	Discipline item 5: make a joke, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddiprai	Discipline item 7a: which twin praised more by you (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddipraip	Discipline item 7a: which twin praised more by partner (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddipuni	Discipline item 7d: which twin punished more by you (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddipunip	Discipline item 7d: which twin punished more by partner (4 Year), see value labels	parent	item	integer	ordinal	1=1st born much more, 2=1st born a little more, 3=about the same, 4=2nd born a little more, 5=2nd born much more
ddisavo1/2	Avoidance parental discipline composite: ask/joke (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddishou	Discipline item 2: shout/tell off, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddishou1/2	Discipline item 2: shout/tell off, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddishoud	Discipline item 2: shout/tell off, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddismak	Discipline item 1: smack or slap, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never, 2, 3=sometimes, 4, 5=usually
ddismak1/2	Discipline item 1: smack or slap, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddismakd	Discipline item 1: smack or slap, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
ddisneg1/2	Negative/harsh parental discipline composite: smack/shout (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddispos1/2	Positive parental discipline composite: explain/firm (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddis1/2	Parental discipline overall scale (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
ddrawt1/2	Drawing test total score (4 Year), 0-9	child	derived	integer	scale	0 to 9
ddrcheap	Dress twins similarly: its cheaper (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddrdiff	Tell twins apart by their dress (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddreasy	Dress twins similarly: its easy (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddress	Dress twins similarly (4 Year), see value labels	parent	item	integer	nominal	0=no never, 1=yes usually, 2=yes sometimes, 3=no but I coordinate their clothes
ddrgiven	Dress twins similarly: given matching clothes (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddrilike	Dress twins similarly: like them to match (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddrother	Dress twins similarly: other reason (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddrpknow	Dress twins similarly: people know they are twins (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
ddrtwlik	Dress twins similarly: they like it (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
demot1/2	Overall (SDQ + Behar) Emotion scale (4 Year), 0-12	child	derived	decimal	scale	0 to 12
derisk1/2	Twin Environment Risk composite (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
deriskf	Family Environment Risk composite (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dexcludm	General exclusion combined with moderate twin age rules (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dexcluds	General exclusion combined with strict twin age rules (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dfamfdia	Health item 24: family history, father: diabetes mellitus (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfamfhbp	Health item 24: family history, father: high blood pressure (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfamfhd	Health item 24: family history, father: heart disease (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfamfwt	Health item 24: family history, father: weight problems (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfammdia	Health item 24: family history, mother: diabetes mellitus (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfammhbp	Health item 24: family history, mother: high blood pressure (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfammhd	Health item 24: family history, mother: heart disease (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfammwt	Health item 24: family history, mother: weight problems (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dfbmcat	Father BMI category (4 Year), see value labels	child	derived	integer	ordinal	1=under weight, 2=normal, 3=over weight, 4=obese
dfbmi	Father BMI (4 Year), kilograms per square metre	child	derived	decimal	quantitative	approx. 18 to 40 (kilograms per square metre)
dfemale1/2	Female gender role scale (4 Year), 12-60	child	derived	decimal	scale	12 to 60
dfhtcm	Father height (4 Year), centimetres	child	item	integer	quantitative	approx. 150 to 200 (centimetres)
dfouryr	4 Year data present, 1Y 0N	parent, child	item	integer	nominal	0=no, 1=yes
dfwscm	Father waist size (4 Year), centimetres	child	item	integer	quantitative	approx. 70 to 130 (centimetres)
dfwtkg	Father weight (4 Year), kilograms	child	item	decimal	quantitative	approx. 55 to 130 (kilograms)
dgboard	Twin play item 8: board games, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dgboard1/2	Twin play item 8: board games, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgboardd	Twin play item 8: board games, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgbooks	Twin play item 5: childrens books, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=none, 2=1-10, 3=11-50, 4=51-100, 5=101 or more
dgbooks1/2	Twin play item 5: childrens books, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgbooksd	Twin play item 5: childrens books, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgcoord	Twin play item 9: do twins have coordination toys (4 Year), see value labels	parent	item	integer	ordinal	2=always available, 1=usually put away, 0=no or not yet
dgdough	Twin play item 9: do twins have play dough/clay (4 Year), see value labels	parent	item	integer	ordinal	2=always available, 1=usually put away, 0=no or not yet
dgender1/2	Gender role total scale (4 Year), 0-100	child	derived	decimal	scale	0 to 100
dgfac11/2	Twin play scale 1: books/puzzles/tapes (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgfac21/2	Twin play scale 2: games (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dggfac1z	Twin play per-family scale 1: outdoor toys (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dggfac2z	Twin play per-family scale 2: indoor toys (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgmessy	Twin play item 1: messy play, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dgmessy1/2	Twin play item 1: messy play, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgmessyd	Twin play item 1: messy play, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgmobile	Twin play item 9: do twins have hanging mobile (4 Year), see value labels	parent	item	integer	ordinal	2=always available, 1=usually put away, 0=no or not yet
dgmusi	Twin play item 3: music player, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dgmusi1/2	Twin play item 3: music player, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgmusic	Twin play item 3: do twins have music player (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dgmusid	Twin play item 3: music player, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgoutdor	Twin play item 9: do twins have outdoor toys (4 Year), see value labels	parent	item	integer	ordinal	2=always available, 1=usually put away, 0=no or not yet
dgphys	Twin play item 7: physical games, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dgphys1/2	Twin play item 7: physical games, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgphysd	Twin play item 7: physical games, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgpsamec	Twins are in the same class at play group (4 Year), see value labels	parent	item	integer	ordinal	0=no, 1=yes sometimes, 2=yes always
dgpsamen	Twins attend the same play group (4 Year), see value labels	parent	item	integer	ordinal	0=no, 1=yes sometimes, 2=yes always
dgpuzz	Twin play item 2: puzzles, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=none, 2=1-3, 3=4-6, 4=7-10, 5=11 or more
dgpuzz1/2	Twin play item 2: puzzles, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgpuzzd	Twin play item 2: puzzles, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgramma1/2	Grammar composite score (4 Year), 0-2	child	derived	integer	scale	0, 1 or 2
dgtapes	Twin play item 4: childrens recordings, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=none, 2=1-3, 3=4-6, 4=7-10, 5=11 or more
dgtapes1/2	Twin play item 4: childrens recordings, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgtapesd	Twin play item 4: childrens recordings, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dgtricyc	Twin play item 9: do twins have tricycles/scooters (4 Year), see value labels	parent	item	integer	ordinal	2=always available, 1=usually put away, 0=no or not yet
dgzoo	Twin play item 6: taken to zoo, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=no, 2=once, 3=2-3 times, 4=4-5 times, 5=6 or more times
dgzoo1/2	Twin play item 6: taken to zoo, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dgzood	Twin play item 6: taken to zoo, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dhache1/2	Health item 5: earache (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhaid1/2	Health item 3: prescribed hearing aid (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dhand1/2	Twin handedness: less stringent classification (4 Year), see value labels	child	derived	integer	nominal	1=left handed, 2=right handed, 3=mixed handedness
dhands1/2	Twin handedness: more stringent classification (4 Year), see value labels	child	derived	integer	nominal	1=left handed, 2=right handed, 3=mixed handedness
dhcatar1/2	Health item 4: catarrh during cold (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhignor1/2	Health item 9: ignore what people saying (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhmouth1/2	Health item 7: mouth breathing (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhosp1/2	Health item 21: admitted to hospital in last year (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dhospca1/2	Health item 22: hospital casualty in last year (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dhospcx1/2	Health item 22a: number of times to hospital casualty in last year (4 Year), see value labels	parent	item	integer	ordinal	1=once, 2=twice, 3=3 or more times
dhospdd1/2	Health item 21b: longest stay in hospital in last year (4 Year), see value labels	parent	item	integer	ordinal	1=1 day, 2=2 days, 3=3-4 days, 4=5 or more days
dhospfa	Father needed hospital (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dhospmo	Mother needed hospital (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dhospsib	Sibling needed hospital (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dhospx1/2	Health item 21a: number of times admitted to hospital (4 Year), see value labels	parent	item	integer	ordinal	1=once, 2=twice, 3=3 or more times
dhpus1/2	Health item 6: pus in ears (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhsnore1/2	Health item 8: snore (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dhsusp1/2	Health item 1: hearing problem: ever suspected (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dhtalk1/2	Health item 2: talking problem (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dhyp11/2	Behaviour item 11: difficulty completing activities (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dhyp21/2	Behaviour item 43: difficulty waiting (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dhyp31/2	Behaviour item 18: touches things not allowed (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dhypt1/2	Overall (SDQ and Behar) Hyperactivity scale (4 Year), 0-20	child	derived	decimal	scale	0 to 20
dillfa	Father seriously ill (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dillfam	Serious illness in the family (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dillmo	Mother seriously ill (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dillsib	Sibling seriously ill (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
djobch	Has respondent job changed (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
djobchp	Has partner job changed (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=do not have a partner
dlangown	Twins have their own language (4 Year), see value labels	parent	item	integer	nominal	0=no never, 1=yes at the moment, 2=yes in the past
dlangswi	Twins switch in and out of own language (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dld1/2	Health item 18: learning disability (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dlearndif1/2	Health item 18 type of learning disability (4 Year), see value labels	parent	item	integer	nominal	1=speech-related problem, 2=delayed learning, 3=ASD, 4=other
dleft1/2	Twin is left handed: less stringent criteria (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dlifeev	Life events composite: count of events (4 Year), 0-5	parent	derived	integer	scale	0 to 5
dlilamp1/2	Twin goes to sleep with: lamp in room (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dliland1/2	Twin goes to sleep with: landing light (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dlinigt1/2	Twin goes to sleep with: night light (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dlinone1/2	Twin goes to sleep with: no light (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dliroom1/2	Twin goes to sleep with: room light (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dllang1/2	Low language overall (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dllpic1/2	Low language: low dpictot score (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dllslow1/2	Low language: slow language development (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dlltalk1/2	Low language: limited or no talking (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dllvoc1/2	Low language: low dvocab score (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dmale1/2	Male gender role scale (4 Year), 12-60	child	derived	decimal	scale	12 to 60
dmana1/2	Draw-a-man score for drawing arms (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanb1/2	Draw-a-man score for drawing body (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanc1/2	Draw-a-man score for drawing clothes (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmane1/2	Draw-a-man score for drawing eyes (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanea1/2	Draw-a-man score for drawing ears (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanf1/2	Draw-a-man score for drawing feet (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanh1/2	Draw-a-man score for drawing head (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanha1/2	Draw-a-man score for drawing hair (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanhan1/2	Draw-a-man score for drawing hands (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanl1/2	Draw-a-man score for drawing legs (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmanm1/2	Draw-a-man score for drawing mouth (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmann1/2	Draw-a-man score for drawing nose (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dmant1/2	Draw-a-man test total score (4 Year), 0-12	child	derived	integer	scale	0 to 12
dmbmcat	Mother BMI category (4 Year), see value labels	child	derived	integer	ordinal	1=under weight, 2=normal, 3=over weight, 4=obese
dmbmi	Mother BMI (4 Year), kilograms per square metre	child	derived	decimal	quantitative	approx. 15 to 45 (kilograms per square metre)
dmdanx	Maternal depression item 4: anxious or worried (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdblame	Maternal depression item 3: blamed myself (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdcry	Maternal depression item 9: crying (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdenjoy	Maternal depression item 2: enjoy looking forward (4 Year), see value labels	parent	item	integer	ordinal	0=as much as ever, 1=rather less than before, 2=definitely not so much now, 3=hardly/not at all
dmdharm	Maternal depression item 10: thoughts of self harm (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdlaugh	Maternal depression item 1: laugh/see funny side (4 Year), see value labels	parent	item	integer	ordinal	0=as much as ever, 1=rather less than before, 2=definitely not so much now, 3=hardly/not at all
dmdontop	Maternal depression item 6: getting on top of me (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdsad	Maternal depression item 8: sad or miserable (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdscare	Maternal depression item 5: scared or panicky (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmdtot	Maternal depression scale (4 Year), 0-30	parent	derived	decimal	scale	0 to 30
dmdunhap	Maternal depression item 7: unhappy, difficult sleeping (4 Year), see value labels	parent	item	integer	ordinal	0=no never/not at all, 1=not very much, 2=yes sometimes/quite often, 3=yes often/most of the time
dmhtcm	Mother height (4 Year), centimetres	child	item	integer	quantitative	approx. 145 to 190 (centimetres)
dmopreg	Is mother pregnant (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dmstatus	Respondent marital status (4 Year), see value labels	parent	derived	integer	nominal	1=married to parent of twins, 2=married to other, 3=cohabiting with parent of twins, 4=cohabiting with other, 5=divorced, 6=separated, 7=widowed, 8=unmarried
dmwscm	Mother waist size (4 Year), centimetres	child	item	integer	quantitative	approx. 55 to 115 (centimetres)
dmwtkg	Mother weight (4 Year), kilograms	child	item	decimal	quantitative	approx. 40 to 120 (kilograms)
dnapda1/2	Twin still wears nappies during day (4 Year), see value labels	parent	item	integer	ordinal	2=always, 1=sometimes, 0=never
dnapnt1/2	Twin still wears nappies at night (4 Year), see value labels	parent	item	integer	ordinal	2=always, 1=sometimes, 0=never
dodd011/2	Odd One Out item 1 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd01s1/2	Odd One Out item 1 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd021/2	Odd One Out item 2 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd02s1/2	Odd One Out item 2 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd031/2	Odd One Out item 3 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd03s1/2	Odd One Out item 3 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd041/2	Odd One Out item 4 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd04s1/2	Odd One Out item 4 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd051/2	Odd One Out item 5 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd05s1/2	Odd One Out item 5 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd061/2	Odd One Out item 6 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd06s1/2	Odd One Out item 6 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd071/2	Odd One Out item 7 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd07s1/2	Odd One Out item 7 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd081/2	Odd One Out item 8 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd08s1/2	Odd One Out item 8 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd091/2	Odd One Out item 9 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd09s1/2	Odd One Out item 9 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd101/2	Odd One Out item 10 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd10s1/2	Odd One Out item 10 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd111/2	Odd One Out item 11 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd11s1/2	Odd One Out item 11 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd121/2	Odd One Out item 12 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd12s1/2	Odd One Out item 12 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd131/2	Odd One Out item 13 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd13s1/2	Odd One Out item 13 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd141/2	Odd One Out item 14 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd14s1/2	Odd One Out item 14 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd151/2	Odd One Out item 15 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
dodd15s1/2	Odd One Out item 15 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dodd161/2	Odd One Out item 16 response (4 Year), see value labels	child	item	integer	nominal	1/2/3=picture selected, 5=invalid selection
doddre11/2	Odd One Out feedback item 1: cannot do/do not like (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
doddre21/2	Odd One Out feedback item 2: angry/frustrated (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
doddre31/2	Odd One Out feedback item 3: shrug/turn away (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
doddre41/2	Odd One Out feedback item 4: wanted to stop (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
doddt1/2	Odd one out test total score (4 Year), 0-13	child	derived	integer	scale	0 to 13
dpar1/2	Being a parent overall parental feelings scale (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dparca1/2	Parca overall mean score (4 Year), standardised	child	derived	decimal	scale	approx. -3 to +3 (standardised)
dparent	Parent booklet data present (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dparneg1/2	Being a parent twin scale 1: negative feelings (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dparpos1/2	Being a parent twin scale 2: positive feelings (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dpbage	Twin age in years on completion of parent booklet (4 Year)	parent	derived	decimal	quantitative	approx. 3.9 to 4.9 (years)
dpbLLCage	Age of twin when 4 year parent booklet completed (for use in LLC TRE), months	parent	derived	integer	quantitative	approx. 47 to 58 (months)
dpbLLCdate	Date when 4 year parent booklet completed (for use in LLC TRE), yyyy-mm string	parent	derived	string	date value	approx. '1997-12' to '2001-03'
dpd011/2	Drawing item 1 score (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dpd021/2	Drawing item 2 score (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dpd031/2	Drawing item 3 score (4 Year), 0 or 1	child	item	integer	ordinal	0, 1 (scores)
dpd041/2	Drawing item 4 score (4 Year), 0 or 1 or 2	child	item	integer	ordinal	0, 1, 2 (scores)
dpd04h1/2	Drawing item 4 hand used (4 Year), see value labels	child	item	integer	nominal	1=left, 2=right, 3=both
dpd051/2	Drawing item 5 score (4 Year), 0 or 1 or 2	child	item	integer	ordinal	0, 1, 2 (scores)
dpd05h1/2	Drawing item 5 hand used (4 Year), see value labels	child	item	integer	nominal	1=left, 2=right, 3=both
dpd061/2	Drawing item 6 score (4 Year), 0 or 1 or 2	child	item	integer	ordinal	0, 1, 2 (scores)
dpd06h1/2	Drawing item 6 hand used (4 Year), see value labels	child	item	integer	nominal	1=left, 2=right, 3=both
dpdrep11/2	Drawing feedback item 1: cannot do/do not like (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpdrep21/2	Drawing feedback item 2: angry/frustrated (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpdrep31/2	Drawing feedback item 3: shrug/turn away (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpdrep41/2	Drawing feedback item 4: wanted to stop (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpdrink1/2	Twin potty training: no drink before bed (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dpdryda1/2	Twin dry throughout day (4 Year), see value labels	parent	item	integer	ordinal	4=always, 2=mostly, 2=sometimes, 1=hardly ever, 0=never
dpdryexp	Age when you expect twins to be dry at night (4 Year), see value labels	parent	item	integer	ordinal	1=2yrs, 2=2.5yrs, 3=3yrs, 4=3.5yrs, 5=4yrs, 6=4.5yrs, 7=5yrs or older
dpdrynt1/2	Twin dry throughout night (4 Year), see value labels	parent	item	integer	ordinal	4=always, 2=mostly, 2=sometimes, 1=hardly ever, 0=never
dpic011/2	Picture Vocabulary item 1 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic01s1/2	Picture Vocabulary item 1 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic021/2	Picture Vocabulary item 2 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic02s1/2	Picture Vocabulary item 2 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic031/2	Picture Vocabulary item 3 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic03s1/2	Picture Vocabulary item 3 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic041/2	Picture Vocabulary item 4 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic04s1/2	Picture Vocabulary item 4 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic051/2	Picture Vocabulary item 5 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic05s1/2	Picture Vocabulary item 5 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic061/2	Picture Vocabulary item 6 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic06s1/2	Picture Vocabulary item 6 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic071/2	Picture Vocabulary item 7 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic07s1/2	Picture Vocabulary item 7 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpic081/2	Picture Vocabulary item 8 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpic08s1/2	Picture Vocabulary item 8 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpicre11/2	Picture Vocabulary feedback item 1: cannot do/do not like (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpicre21/2	Picture Vocabulary feedback item 2: angry/frustrated (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpicre31/2	Picture Vocabulary feedback item 3: shrug/turn away (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpicre41/2	Picture Vocabulary feedback item 4: wanted to stop (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpictot1/2	Picture vocabulary total score (4 Year), 0-8	child	derived	integer	scale	0 to 8
dplaygp1/2	Twin attends play group (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dplift1/2	Twin potty training: lift without waking (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dpnapp1/2	Twin potty training: try without nappies (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dpottrn1/2	Trying potty training twin now (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dpottrp1/2	Tried potty training twin in past (4 Year), 1Y 0N	parent	derived	integer	nominal	0=no, 1=yes
dpotty1/2	Twin knows when to use toilet/potty during day (4 Year), see value labels	parent	item	integer	ordinal	3=often, 2=sometimes, 1=occasionally, 0=never
dpparbd1/2	Twin potty training: sleep in parent bed (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dpr011/2	Parent-report Parca item 1: tell the time (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr021/2	Parent-report Parca item 2: shoe on correct foot (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr031/2	Parent-report Parca item 3: understands two (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr041/2	Parent-report Parca item 4: knows 20p worth more than 10p (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr051/2	Parent-report Parca item 5: plays counting games (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr061/2	Parent-report Parca item 6: understands age (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr071/2	Parent-report Parca item 7: plants need water (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr081/2	Parent-report Parca item 8: seeds grow if planted (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr091/2	Parent-report Parca item 9: water runs downhill (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr101/2	Parent-report Parca item 10: water level goes up in bath (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr111/2	Parent-report Parca item 11: fridge light goes off (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr12a1/2	Parent-report Parca item 12a: asks about rainbows (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr12b1/2	Parent-report Parca item 12b: asks about dark at night (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr12c1/2	Parent-report Parca item 12c: asks why fridge cold (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr12d1/2	Parent-report Parca item 12d: asks what makes cars go (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpr12e1/2	Parent-report Parca item 12e: asks what makes people ill (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dpreass1/2	Twin potty training: reassure if wet (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dprodia1/2	Health item 17e: problems with diabetes (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dproeye1/2	Health item 17a: problems with eyesight (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprofit1/2	Health item 17g: problems with fits (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprohd1/2	Health item 17d: problems with headaches (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprosto1/2	Health item 17b: problems with stomachaches (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprot1/2	Overall (SDQ and Behar) Prosocial scale (4 Year), 0-16	child	derived	decimal	scale	0 to 16
dprovom1/2	Health item 17c: problems with vomiting (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprowk1/2	Health item 17f: problems with weakness/paralysis (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dprward1/2	Twin potty training: offer rewards (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
dpuz011/2	Puzzle item 1 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz01s1/2	Puzzle item 1 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz021/2	Puzzle item 2 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz02s1/2	Puzzle item 2 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz031/2	Puzzle item 3 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz03s1/2	Puzzle item 3 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz041/2	Puzzle item 4 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz04s1/2	Puzzle item 4 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz051/2	Puzzle item 5 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz05s1/2	Puzzle item 5 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz061/2	Puzzle item 6 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz06s1/2	Puzzle item 6 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz071/2	Puzzle item 7 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz07s1/2	Puzzle item 7 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz081/2	Puzzle item 8 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz08s1/2	Puzzle item 8 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz091/2	Puzzle item 9 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz09s1/2	Puzzle item 9 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz101/2	Puzzle item 10 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz10s1/2	Puzzle item 10 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz111/2	Puzzle item 11 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz11s1/2	Puzzle item 11 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuz121/2	Puzzle item 12 response (4 Year), see value labels	child	item	integer	nominal	1/2/3/4=picture selected, 5=invalid selection
dpuz12s1/2	Puzzle item 12 correct score (4 Year), 1Y 0N	child	derived	integer	ordinal	0=no, 1=yes
dpuzre11/2	Puzzle feedback item 1: cannot do/do not like (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpuzre21/2	Puzzle feedback item 2: angry/frustrated (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpuzre31/2	Puzzle feedback item 3: shrug/turn away (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpuzre41/2	Puzzle feedback item 4: wanted to stop (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dpuzt1/2	Puzzle test total score (4 Year), 0-12	child	derived	integer	scale	0 to 12
dpwake1/2	Twin potty training: wake during night (4 Year), see value labels	parent	item	integer	ordinal	3=often, 1=sometimes, 0=never
drawg1/2	G: overall cognitive ability composite (4 Year), standardised	child	derived	decimal	scale	approx. -3 to +3 (standardised)
dreparc1/2	Parent-reported Parca total score (4 Year), 0-12	child	derived	integer	scale	0 to 12
dright1/2	Twin is right handed: less stringent criteria (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dsay011/2	What Child can Say item 1: how child talks (4 Year), see value labels	child	item	integer	ordinal	1=not talking yet, 2=talking but cannot understand him/her, 3=talking in one word utterances, 4=talking in two to three word phrases, 5=talking in fairly complete sentences, 6=talking in long and complicated sentences
dsay01a1/2	What Child can Say item 1a: not yet talking (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsay021/2	What Child can Say item 2: what do you want (4 Year), 1actions 2words	child	item	integer	nominal	1=actions, 2=words
dsay031/2	What Child can Say item 3: sounds like others same age (4 Year), 1younger 2like others	child	item	integer	nominal	1=sounds a little younger than others the same age, 2=sounds like most others the same age
dsayb011/2	Books item 1: likes being read to (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb021/2	Books item 2: favourite books (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb031/2	Books item 3: recite nursery rhyme (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb041/2	Books item 4: say alphabet (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb04a1/2	Books item 4a: name a letter (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes some letters, 2=yes all letters
dsayb04b1/2	Books item 4b: sound of a letter (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes some letters, 2=yes all letters
dsayb051/2	Books item 5: sound out words (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb061/2	Books item 6: meaning of written word (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb071/2	Books item 7: tell a story once read (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb081/2	Books item 8: write simple sentences (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb091/2	Books item 9: sip/tip/lip sound same (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayb101/2	Books item 10: shirt unlike hall/ball (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc011/2	Communication item 1: concerns about speech/language (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc021/2	Communication item 2: points to show interest (4 Year), see value labels	child	item	integer	ordinal	2=often, 1=sometimes, 0=never
dsayc031/2	Communication item 3: follows line of gaze (4 Year), see value labels	child	item	integer	ordinal	2=usually, 1=sometimes, 0=usually not
dsayc041/2	Communication item 4: upset by small changes (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes slightly upset, 2=yes surprisingly upset
dsayc051/2	Communication item 5: notices small details (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes sometimes, 2=yes very often
dsayc061/2	Communication item 6: uses word for a type (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes sometimes, 2=yes very often
dsayc071/2	Communication item 7: uses word for whole object (4 Year), see value labels	child	item	integer	ordinal	0=no, 1=yes sometimes, 2=yes very often
dsayc081/2	Communication item 8: meaningless fluent speech (4 Year), see value labels	child	item	integer	ordinal	2=often, 1=sometimes, 0=never
dsayc091/2	Communication item 9: echoes what others say (4 Year), see value labels	child	item	integer	ordinal	2=often, 1=sometimes, 0=never
dsayc101/2	Communication item 10: recites rhymes (4 Year), see value labels	child	item	integer	ordinal	2=yes unusually often, 1=yes sometimes, 0=never
dsayc111/2	Communication item 11: language in decline (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1a1/2	Communication item 1a: language developing slowly (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1b1/2	Communication item 1b: hard to understand (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1c1/2	Communication item 1c: not understand others (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1d1/2	Communication item 1d: pronounces poorly (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1e1/2	Communication item 1e: does not hear well (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1f1/2	Communication item 1f: stutters (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1g1/2	Communication item 1g: other concern (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayc1h1/2	Communication item 1h: seen professional (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl011/2	Language item 1: how old (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl021/2	Language item 2: birthday (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl031/2	Language item 3: past events (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl041/2	Language item 4: future events (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl051/2	Language item 5: tell story (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl061/2	Language item 6: right and left (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl071/2	Language item 7: uses -est words (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl081/2	Language item 8: today (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl091/2	Language item 9: yesterday (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl101/2	Language item 10: accident/on purpose (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl121/2	Language item 12: asks what words mean (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl131/2	Language item 13: but (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl141/2	Language item 14: before and after (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayl151/2	Language item 15: play with language (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayn011/2	Numbers item 1: count 1 to 10 (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayn021/2	Numbers item 2: write 1 to 10 (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayn031/2	Numbers item 3: 5 or 2 bigger (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayn041/2	Numbers item 4: simple adding (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dsayn051/2	Numbers item 5: simple subtraction (4 Year), 1Y 0N	child	item	integer	nominal	0=no, 1=yes
dscnv1/2	Non-verbal cognitive ability composite (4 Year), standardised	child	derived	decimal	scale	approx. -3 to +3 (standardised)
dscv1/2	Verbal cognitive ability composite (4 Year), standardised	child	derived	decimal	scale	approx. -3 to +3 (standardised)
dsdqbeht1/2	SDQ total behaviour problems scale (4 Year), 0-38	child	derived	decimal	scale	0 to 38
dsdqcon11/2	Behaviour item 50: temper tantrums (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqcon21/2	Behaviour item 27: obedient (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqcon2r1/2	Reversed version of behaviour item 27 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqcon31/2	Behaviour item 12: fights other children (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqcon41/2	Behaviour item 34: lies or cheats (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqcon51/2	Behaviour item 5: steals (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqcont1/2	SDQ Conduct scale (4 Year), 0-10	child	derived	decimal	scale	0 to 10
dsdqemo11/2	Behaviour item 31: frequent stomachaches or sickness (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqemo21/2	Behaviour item 19: worried (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqemo31/2	Behaviour item 24: unhappy (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqemo51/2	Behaviour item 10: easily scared (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqemot1/2	SDQ Emotion scale (4 Year), 0-8	child	derived	decimal	scale	0 to 8
dsdqhyp1/2	Behaviour item 2: restless (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqhyp21/2	Behaviour item 6: fidgets (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqhyp31/2	Behaviour item 14: easily distracted (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqhyp41/2	Behaviour item 13: thinks before acting (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqhyp4r1/2	Reversed version of behaviour item 13 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqhyp51/2	Behaviour item 32: sees tasks through (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqhyp5r1/2	Reversed version of behaviour item 32 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqhypt1/2	SDQ Hyperactivity scale (4 Year), 0-10	child	derived	decimal	scale	0 to 10
dsdqper11/2	Behaviour item 20: solitary (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqper21/2	Behaviour item 35: has a good friend (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqper2r1/2	Reversed version of behaviour item 35 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqper31/2	Behaviour item 15: liked by other children (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqper3r1/2	Reversed version of behaviour item 15 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqper41/2	Behaviour item 28: bullied (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqper51/2	Behaviour item 29: gets on better with adults (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqpert1/2	SDQ Peer problems scale (4 Year), 0-10	child	derived	decimal	scale	0 to 10
dsdqpro11/2	Behaviour item 3: considerate (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqpro21/2	Behaviour item 48: shares with other children (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqpro2r1/2	Reversed version of behaviour item 48 (4 Year), see value labels	child	item	integer	ordinal	0=certainly true, 1=sometimes, 2=not true
dsdqpro31/2	Behaviour item 22: helps people if hurt (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqpro41/2	Behaviour item 30: kind to young children (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqpro51/2	Behaviour item 17: volunteers to help (4 Year), see value labels	child	item	integer	ordinal	0=not true, 1=sometimes true, 2=certainly true
dsdqprot1/2	SDQ Prosocial scale (4 Year), 0-10	child	derived	decimal	scale	0 to 10
dseengp1/2	Health item 19: seen GP in last year (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dseengx1/2	Health item 19a: number of times seen GP in last year (4 Year), see value labels	parent	item	integer	ordinal	1=1, 2=2, 3=3, 4=4, 5=5-6, 6=7-10, 7=over 10 times
dsept1/2	General Separation anxiety scale (4 Year), 0-4	child	derived	decimal	scale	0 to 4
dsibnew	New siblings living at home (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskage1/2	Health item 13: age when skin problem started (4 Year), see value labels	parent	item	integer	ordinal	1=0-3 months, 2=4-6 months, 3=7-12 months, 4=1-2 years, 5=2-3 years, 6=over 3 years
dskarms1/2	Health item 12d: skin problem on arms (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskbody1/2	Health item 12d: skin problem on whole body (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskface1/2	Health item 12a: skin problem on face (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskhead1/2	Health item 12d: skin problem on head (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskitch1/2	Health item 10: skin problems with itching (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes at the moment, 2=yes previously
dskknee1/2	Health item 12b: skin problem on knee/elbow (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dsklegs1/2	Health item 12d: skin problem on legs (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dsktorso1/2	Health item 12d: skin problem on torso (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dsktrt1/2	Health item 11: skin treatment (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dskwris1/2	Health item 12c: skin problem on wrist/ankle (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dslearl1/2	Twin sleep problem: waking early (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dslnmar1/2	Twin sleep problem: nightmares (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dslprob1/2	Twin sleep problem: difficulty getting to sleep (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dslwake1/2	Twin sleep problem: frequent waking (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dsurage1/2	Health item 23a: age on first operation in last year (4 Year), see value labels	parent	item	integer	ordinal	1=3 years to 3 years 3 months, 2=3 years and 4-6 months, 3=3 years and 7-9 months, 4=3 years 10 months to 4 years
dsurgga1/2	Health item 23b: operation needed general anaesthetic (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dsurgry1/2	Health item 23: surgical operation in last year (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dtbook	Talking to twins item 6: read books, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dtbook1/2	Talking to twins item 6: read books, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtbookd	Talking to twins item 6: read books, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dteat	Talking to twins item 8: choose what to eat, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dteat1/2	Talking to twins item 8: choose what to eat, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dteatd	Talking to twins item 8: choose what to eat, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dtempzyg	Zygosity difference scale (4 Year), 0-1	parent	derived	decimal	scale	0 to 1
dtfac11/2	Talking to twin scale 1: pronunciation/sentences/words (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtfac21/2	Talking to twin scale 2: rhymes/books/locations/talk (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtloca	Talking to twins item 5: directions/locations, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dtloca1/2	Talking to twins item 5: directions/locations, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtlocad	Talking to twins item 5: directions/locations, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dtoleft1/2	Twin is left handed: more stringent criteria (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dtorigh1/2	Twin is right handed: more stringent criteria (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dtpron	Talking to twins item 2: correct mispronunciation, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never or rarely, 2=occasionally, 3=about half the time, 4=quite often, 5=almost always
dtpron1/2	Talking to twins item 2: correct mispronunciation, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtprond	Talking to twins item 2: correct mispronunciation, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dtrhym	Talking to twins item 1: rhymes/songs/prayers, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dtrhym1/2	Talking to twins item 1: rhymes/songs/prayers, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtrhymd	Talking to twins item 1: rhymes/songs/prayers, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dtsent	Talking to twins item 3: correct sentences, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never or rarely, 2=occasionally, 3=about half the time, 4=quite often, 5=almost always
dtsent1/2	Talking to twins item 3: correct sentences, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtsentd	Talking to twins item 3: correct sentences, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dttalk	Talking to twins item 7: talk around house, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=less than once monthly, 2=once or twice monthly, 3=once or twice weekly, 4=several times weekly, 5=almost daily
dttalk1/2	Talking to twins item 7: talk around house, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dttalkd	Talking to twins item 7: talk around house, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dtvoc1/2	Transformed MCDI vocabulary total score (4 Year), 0-48	child	derived	decimal	scale	0 to 48
dtwbage1/2	Twin age in years on completion of twin booklet (4 Year)	child	derived	decimal	quantitative	approx. 3.1 to 4.9 (years)
dtwbagediff	Difference in twin ages on completion of twin booklets (4 Year), years	child	derived	decimal	quantitative	approx. 0 to 0.7 (years)
dtwbLLCage1	Age of twin when 4 year twin booklet completed (for use in LLC TRE), months	child	derived	integer	quantitative	approx. 47 to 57 (months)
dtwbLLCdate1	Date when 4 year twin booklet completed (for use in LLC TRE), yyyy-mm string	child	derived	string	date value	approx. '1997-12' to '2001-03'
dtwdata1/2	Twin booklet data present (4 Year), 1Y 0N	child	derived	integer	nominal	0=no, 1=yes
dtword	Talking to twins item 4: correct wrong word, elder twin frequency (4 Year), see value labels	parent	item	integer	ordinal	1=never or rarely, 2=occasionally, 3=about half the time, 4=quite often, 5=almost always
dtword1/2	Talking to twins item 4: correct wrong word, twin-specific (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dtwordd	Talking to twins item 4: correct wrong word, younger twin difference (4 Year), see value labels	parent	item	integer	ordinal	1=lot more, 2=little more, 3=about equally, 4=little less, 5=lot less
dvc011/2	Vocabulary item 1: can say bird (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc021/2	Vocabulary item 2: can say finger (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc031/2	Vocabulary item 3: can say plant (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc041/2	Vocabulary item 4: can say measure (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc051/2	Vocabulary item 5: can say tortoise (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc061/2	Vocabulary item 6: can say shoulder (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc071/2	Vocabulary item 7: can say parent (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc081/2	Vocabulary item 8: can say peel (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc091/2	Vocabulary item 9: can say ball (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc101/2	Vocabulary item 10: can say skeleton (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc111/2	Vocabulary item 11: can say hungry (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc121/2	Vocabulary item 12: can say dive (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc131/2	Vocabulary item 13: can say pencil (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc141/2	Vocabulary item 14: can say children (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc151/2	Vocabulary item 15: can say furry (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc161/2	Vocabulary item 16: can say drip (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc171/2	Vocabulary item 17: can say juice (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc181/2	Vocabulary item 18: can say doctor (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc191/2	Vocabulary item 19: can say polite (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc201/2	Vocabulary item 20: can say will (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc211/2	Vocabulary item 21: can say tool (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc221/2	Vocabulary item 22: can say dentist (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc231/2	Vocabulary item 23: can say courage (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc241/2	Vocabulary item 24: can say excited (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc251/2	Vocabulary item 25: can say envelope (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc261/2	Vocabulary item 26: can say hero (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc271/2	Vocabulary item 27: can say nuisance (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc281/2	Vocabulary item 28: can say healthy (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc291/2	Vocabulary item 29: can say tap (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc301/2	Vocabulary item 30: can say insect (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc311/2	Vocabulary item 31: can say down (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc321/2	Vocabulary item 32: can say lucky (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc331/2	Vocabulary item 33: can say castle (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc341/2	Vocabulary item 34: can say caterpillar (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc351/2	Vocabulary item 35: can say under (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc361/2	Vocabulary item 36: can say calm (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc371/2	Vocabulary item 37: can say stamp (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc381/2	Vocabulary item 38: can say vehicle (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc391/2	Vocabulary item 39: can say half (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc401/2	Vocabulary item 40: can say uncomfortable (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc411/2	Vocabulary item 41: can say triangle (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc421/2	Vocabulary item 42: can say fruit (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc431/2	Vocabulary item 43: can say last (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc441/2	Vocabulary item 44: can say lonely (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc451/2	Vocabulary item 45: can say eye (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc461/2	Vocabulary item 46: can say furniture (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc471/2	Vocabulary item 47: can say make (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvc481/2	Vocabulary item 48: can say shy (4 Year), 1Y 0N	child	item	integer	ordinal	0=no, 1=yes
dvocab1/2	MCDI vocabulary total score (4 Year), 0-48	child	derived	integer	scale	0 to 48
dyhbed	Home chaos item 1: regular bedtime (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dyhcalm	Home chaos item 6: calm atmosphere (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dyhfac1z	Home chaos per-family scale 1: chaotic (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dyhfac2z	Home chaos per-family scale 2: calm (4 Year), standardised	parent	derived	decimal	scale	approx. -3 to +3 (standardised)
dyhhear	Home chaos item 2: cannot hear yourself think (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dyhontop	Home chaos item 4: stay on top of things (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dyhtv	Home chaos item 5: television usually on (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dyhzoo	Home chaos item 3: its a real zoo (4 Year), see value labels	parent	item	integer	ordinal	1=untrue, 2, 3, 4, 5=true
dzyblood	Twin blood groups known (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dzyears	Differences in ear lobes (4 Year), see value labels	parent	item	integer	ordinal	1=no difference, 2=only slight difference, 3=clear difference
dzyeyes	Differences in eye colour (4 Year), see value labels	parent	item	integer	ordinal	1=no difference, 2=only slight difference, 3=clear difference
dzyfac	Different blood rhesus factors (4 Year), 1Y 0N	parent	item	integer	ordinal	0=no (same), 1=yes (different)
dzyfind	Interested in finding out zygosity (4 Year), see value labels	parent	item	integer	ordinal	1=very, 2=a little, 3=not really, 4=definitely not
dzygrow	Likeness changed as twins grown older (4 Year), see value labels	parent	item	integer	nominal	1=remainded the same, 2=become less similar, 3=become more similar
dzyhairs	Differences in hair shade (4 Year), see value labels	parent	item	integer	ordinal	1=no difference, 2=only slight difference, 3=clear difference
dzyhairt	Differences in hair texture (4 Year), see value labels	parent	item	integer	ordinal	1=no difference, 2=only slight difference, 3=clear difference
dzymistb	Mistake twins for each other: babysitter/carer (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymistc	Mistake twins for each other: parents casual friends (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymistf	Mistake twins for each other: parents close friends (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymistm	Mistake twins for each other: people meeting first time (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymistp	Mistake twins for each other: other parent (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymistr	Mistake twins for each other: other relatives (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzymists	Mistake twins for each other: older siblings (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=rarely or never
dzyofbir	Would have agreed to zygosity test at birth (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes definitely, 2=yes maybe
dzyofnow	Would agree to zygosity test if offered now (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes definitely, 2=yes maybe
dzyold	Recoded likeness changed as twins grown older (4 Year), see value labels	parent	item	integer	ordinal	1=become more similar, 2=remained the same, 3=become less similar
dzypeas	Respondent opinion of twin likeness (4 Year), see value labels	parent	item	integer	ordinal	1=alike as two peas in a pod, 2=as alike as brothers and sisters, 3=not much alike
dzyphot2	Recoded tell twins apart in photos (4 Year), see value labels	parent	item	integer	ordinal	1=no often confuse them, 2=yes but sometimes hard, 3=yes easily tell them apart
dzyphoto	Tell twins apart in photos (4 Year), see value labels	parent	item	integer	nominal	0=no often confuse them, 1=yes easily tell them apart, 2=yes but sometimes hard
dzyphysi	Physical differences not visible (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dzyprobs	Differences because of birth problems/accident/illness (4 Year), see value labels	parent	item	integer	nominal	0=no, 1=yes, 2=don't know, 3=there are no differences
dzyprof	Zygosity told by health professional (4 Year), 1MZ 2DZ	parent	item	integer	ordinal	1=MZ, 2=DZ
dzysure	Respondent knows zygosity for sure (4 Year), 1Y 0N	parent	item	integer	nominal	0=no, 1=yes
dzyteet2	Recoded differences in teeth coming through (4 Year), see value labels	parent	item	integer	ordinal	1=matching teeth within a few days, 2=not matching or not within a few days
dzyteeth	Differences in teeth coming through (4 Year), see value labels	parent	item	integer	nominal	1=matching teeth on same side within a few days, 2=matching teeth on opposite sides within a few days, 3=different teeth within a few days, 4=not within a few days of each other, 5=teeth have not come through yet
dzytoget	Twins mistaken when together (4 Year), see value labels	parent	item	integer	ordinal	1=yes often, 2=yes sometimes, 3=no almost never, 4=not mistaken for one another
dzytyp	Different blood groups (4 Year), 1Y 0N	parent	item	integer	ordinal	0=no (same), 1=yes (different)
dzyyou	Zygosity opinion of respondent (4 Year), 1MZ 2DZ	parent	item	integer	ordinal	1=MZ, 2=DZ