Study Emde et al. (1992): study US Colorado 1986

Public

14 months aged, same-sex twin pairs, Colorado, United States, 1986-1989

Sample

Respondents

N = 398

Non Response

Assessment

Behavioural observation
At 14 months: observation at home, 2 weeks later observation in laboratory

Correlate

Authors's Label

Happiness of Twin siblings

Our Classification

Remarks

monozygotic (MZ) = identical dizygotic (DZ) = non-identical Heritability (h²): the extent to which observed variance in behavior can be attributed to genetic influence: -> doubling the difference between the MZ and DZ correlations, because MZ twins are identical genetically, whereas the genetic correlation for DZ twins is assumed to be +.50 Shared Environment (c²): shared environmental influences (c²), estimated in the twin method as twin resemblance not explained by heritability: twice the DZ correlation minus the MZ correlation (only detects major effects of shared environment) for details of computations see DeFries & Fulker, 1985

Distribution

N:  99 monozygotic twin pairs, 99 dizygotic twin pairs

Related specification variables

Operationalization

at 14 months, twin pairs were first observed at home and 2 weeks after that in the laboratory at the Institute for Behavioral Genetics in Boulder, behavior was videotaped and rated afterwards; parents completed questionnaire in the time between the home &  lab session;

Observed Relation with Happiness