Genetic and environmental influences on change in child activity level during
infancy and toddlerhood
Laura V. Scaramella, Daniel S. Shaw,
Melissa A. Barnett, Ginger Moore, and
Rand D. Conger
Characteristics of infant temperament Conceptualizations of temperament often
emphasize: emotional valence (e.g., positive vs. negative), motivation (e.g., approach vs. avoidance), and activity level (Frick, 2006; Nigg, 2006; Rothbart
& Bates, 1998; Rothbart & Posner, 2002).
Characteristics of infant temperament Empirical research often focuses on
combinations of characteristics Fearful temperament = high levels of negative
emotional valence & avoidance motivation and low activity level
Surgency = high levels of positive emotional valence, approach, & activity level
Characteristics of infant temperament Characteristics of temperament may be
differentially influenced by genetic or environmental circumstances
Present investigation considered genetic & environmental influences on child activity level from 9 to 18 months
Infant activity level & adult personality Infancy temperamental characteristics predict
adult personality characteristics (e.g., Caspi, et al., 2003)
High activity level measured during infancy and childhood linked to Less constraint More sensation seeking during adulthood
(e.g., Caspi & Silva, 1995; Rothbart & Posner, 2002)
Nature & nurture influences Continuities in temperament and personality
over time suggest genetic influences Environment has been found to moderate the
expression of temperamental characteristics (e.g., Bates, Pettit, Dodge, & Ridge, 1998)
Adoption design – evaluate both genetic and environmental influences
Study hypotheses Genetic influences:
Adopted children’s high activity level will be positively correlated with birth mothers’ surgency
Environmental influences After controlling for birth mother surgency,
adopted children’s activity level and adoptive mothers’ parenting will be reciprocally related.
Study design: Early Growth & Development Study Adoption study, includes:
361 children adopted at birth Adopted parents Birth mothers Subsample of birth fathers
Current study used data collected when Infants were 9 & 18 months Birth mothers were 3 months post-delivery
Sample characteristics 361 yoked family units participated
Birth mother, adopted child, adoptive parents Average age at first participation
Birth mothers: 23.8 years Adopted children: 8.8 mo Adoptive mothers: 37.0 years Adoptive fathers: 37.9 years
Sample characteristics, con’t Most frequently reported annual income
Birth mother < $20,000 Adoptive parents > $100,000
Average education level Birth mother = some trade school Adoptive parents = college graduate
Ethnicity Birth mother = 78% white Adoptive parents = 90% white
Measures:Birth mother temperamental surgency Birth mother temperamental surgency/extroversion
Adult Temperament Questionnaire (Derryberry & Rothbart, 1988)
Birth mother reports = adopted child ~ 18mo 7 point scale (1 = extremely untrue; 7 = extremely true) Mean of items from 3 subscales (high scores = more surgent)
High intensity pleasure (7 items; = .62) Sociability (5 items; = .72) Positive affect (5 items; = .57)
Measures:Adopted child activity level Adoptive father reports 9 months:
Infant Behavior Questionnaire (Rothbart, 1981) 7 point scale (1 = never; 7 = always) (17 items; = .80)
18 months: Toddler Behavior Questionnaire (Goldsmith, 1996) 7 point scale (1 = never; 7 = always) (20 items; = .79)
Measures:Adoptive mother parenting Two parenting measures
Parental efficacy (Teti & Gefland, 1981) how effective mother feels in managing child Sum of 10 items; 9mo = .73; 18mo = .72 4-point scale (1 = not good at all; 4 = very good)
Parenting daily hassles (Crnic & Greenberg, 1990) Frequency of challenging behavior Sum of 7 items; 9 mo = .76; 18mo = .58 4-point scale (1 = rarely; 4 = constantly)
Means & Standard Deviations of Study Constructs
Mean SD
Birth Mother Surgency 4.57 0.84
AC Activity level (9mo) 3.92 0.75
AC Activity level (18mo) 4.16 0.62
AM Parenting efficacy (9mo) 34.76 2.63
AM Parenting efficacy (18mo) 33.95 2.65
AM Parenting challenges (9mo) 11.72 4.93
AM Parenting challenges (18mo) 13.94 3.44
Correlations among study constructs
1 2 3 4 5 6
1. Bm surgency 1.0
2. Activity: 9m -.07 1.0
3. Activity: 18m .11+ .41** 1.0
4. Efficacy: 9m .02 -.06 -.14* 1.0
5. Efficacy:18m .03 -.14* -.24** .56** 1.0
6. Challenges: 9m -.07 -.08 .18** -.21** -.22** 1.0
7. Challenges: 18m -.07 -.02 .21** -.12* -.19** 63**
Note: + p < .10; * p < .05; ** p < .01.
Results of the hypothesis testing Structural equation models (AMOS 5.0) were
estimated to test each hypothesis After considering genetic influences on AC
activity level, AC activity level and AM parenting efficacy (HYP 1) and perceptions of parenting challenges (HYP2) would be reciprocally related
HYP 1: Parenting EfficacyBirth Mother
Surgency
d2 d4Adoptive MotherParental Efficacy
9 months
Adoptive MotherParental Efficacy
18 months
1
Adopted ChildActivity Level
9 months
Adopted ChildActivity Level
18 monthsd1
1 d31
1
.16**-.05
.40**
.56**
-.12*
-.10*
Fit Indices:2(2) = 0.13RMSEA = .000CFI = 1.00
-.10-.17**
Birth MotherSurgency
d2 d4Adoptive Mother
Parenting Hassles9 months
Adoptive MotherParenting Hassles
18 months
1
Adopted ChildActivity Level
9 months
Adopted ChildActivity Level
18 monthsd1
1 d31
1
HYP 2: Parenting Challenges
.16**-.05
.40**
.63**
.21**
.03
Fit Indices:2(2) = 0.83RMSEA = .000CFI = 1.00
-.08 .18*
Genetic influences & activity level Commonalities in Birth Mother surgency and
AC activity level seem to exist. Limited contact between birth mothers and
adopted children Genetic influence seems to be delayed,
emerging at 18 mos rather than at 9 mos
Environment & activity level HYP 1: Parenting efficacy – Evidence for
reciprocity More 9mo parenting efficacy predicted declines
in activity level Higher 9mo activity level undermined parenting
efficacy
Environment & activity level HYP2: Parenting challenges – No evidence of
reciprocity More perceived parenting challenges at 9mo
predicted increases in activity level Child activity level had little impact on change in
mothers’ perceptions of parenting hassles
Strengths Independent reports of each factor
Genetic factor = Birth mothers Child activity level = Adoptive Fathers Parenting = Adoptive Mothers
Longitudinal design Evaluate the timing of genetic influences Consider environmental influences on change in
behavior
Limitations Unique study design
Adoption studies are rare Participants may be unique
No DNA Behavioral measures of surgency and activity
level are a proxy for molecular genetic measures Currently collecting DNA from the sample
General Conclusions Temperamental characteristic of activity level
seems to be influenced by Genetic factors – BM temperamental surgency Environmental factors – Parenting efficacy and
perceptions of parenting hassles Children’s activity level seems to impact the
environment by undermining parents’ feelings of efficacy.
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