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.