Correlational finding on Happiness and Happiness of sibblings
Subject code: H08ac04

StudyEmde et al. (1992): study US Colorado 1986
TitleTemperament, Emotion, and Cognition at Fourteen Months: The MacArthur Longitudinal Twin Study
SourceChild Development, Vol. 63, No. 6 (Dec., 1992), pp.1437-1455
Public14 months aged, same-sex twin pairs, Colorado, United States, 1986-1989
SampleNon-probability purposive sample
Respondents N =398

Author's labelHappiness of Twin siblings
Page in Source 1445, 1447, 1448
Our classificationHappiness of sibblings, code H08ac04
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 
Observed distributionN: 99 monozygotic twin pairs, 99 dizygotic twin pairs
monozygotic (MZ) = identical
dizygotic (DZ) = non-identical

Heritability (h):
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 (c):
shared environmental influences (c), 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 

for details of computations see DeFries & Fulker, 1985

Observed Relation with Happiness
A-CA-mi-tsb-v-7-ar=+.19 p < .01
Monozygotic Twins
A-CA-mi-tsb-v-7-ar=+.02 ns
Dizygotic Twins
Heritability component:       h=+.34 (ns)
Shared environment component: c=-.15 (ns)

Appendix 1: Happiness measures used
CodeFull Text
A-CA-mi-tsb-v-7-aTime sampling of prevalent mood during free play and Bayley test. Average of observations at 30 second intervals across 15 minutes of free play and 1 minute intervals for 4 alternate 5 minute segments of the Bayley test

Rated on 7 step scale, scale labels not reported

Appendix 2: Statistics used
rPRODUCT-MOMENT CORRELATION COEFFICIENT (Also "Pearson's correlation coefficient' or simply 'correlation coefficient')
Type: test statistic.
Measurement level: Correlate: metric, Happiness: metric
Range: [-1; +1]

r = 0 no correlation ,
r = 1 perfect correlation, where high correlate values correspond with high happiness values, and
r = -1 perfect correlation, where high correlate values correspond with low happiness values.
Ruut Veenhoven, World Database of Happiness, Collection of Correlational Findings, Erasmus University Rotterdam.