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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
Remarks
MZ = monozygotic (non-identical twins) DZ = dizygotic (identical twins)
Related specification variables
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)