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Correlational findings

Study Robinson et al. (2001): study US 1986

Public:
Toddlers, same-sex twins, Colorado, United States, followed from 14 to 24 months of age, 1986-1989
Survey name:
Unnamed study
Sample:
Respondents:
N = 400
Non Response:
Assessment:
Behavioural observation
behavioral observation at home and in laboratory, recorded on video tape; parental reports in questionnaire

Correlate

Authors's label
Happiness of twin sibling
Our Classification
Operationalization
Happiness of twin sibling assessed in the same way using time sampling of expressive behavior

Observed Relation with Happiness

Happiness Measure Statistics Elaboration / Remarks A-CA-mi-tsb-v-4-a r = + p < .01 MONOZYGOTIC:
at 14 months: r=+.50
at 20 months: r=+.55
at 24 months: r=+.26
A-CA-mi-tsb-v-4-a r = + p < .01 DIZYGOTIC:
at 14 months: r=+.39 p<0.01
at 20 months: r=+.34 p<0.01
at 24 months: r=+.18 p<0.05
A-CA-mi-tsb-v-4-a = + HERITABILITY:
at 14 months: h²=+.22 ns
at 20 months: h²=+.40 p<.05
at 24 months: h²=+.16 ns

h² computed using regression method of DeFries & Fulker (1985)
A-CA-mi-tsb-v-4-a = + COMMON ENVIRONMENTAL INFLUENCES:
at 14 months: c²=+.28 ns
at 20 months: c²=+.14 ns
at 24 months: c²=+.10 ns

see Plomin et al. (1990, 1993);
c² computed by using regression method of DeFries & Fulker (1985)