Correlational findings

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

14 months aged, same-sex twin pairs, Colorado, United States, 1986-1989
N = 398
Non Response:
Behavioural observation
At 14 months: observation at home, 2 weeks later observation in laboratory


Authors's label
Happiness of Twin siblings
Our Classification
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
N:  99 monozygotic twin pairs, 99 dizygotic twin pairs
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

Happiness Measure Statistics Elaboration / Remarks A-CA-mi-tsb-v-7-a r = +.19 p < .01 Monozygotic Twins A-CA-mi-tsb-v-7-a r = +.02 ns Dizygotic Twins A-CA-mi-tsb-v-7-a = Heritability component:       h²=+.34 (ns)
Shared environment component: c²=-.15 (ns)