Contingent parental investment: An evolutionary framework for understanding early interaction between mothers and children David Beaulieu, Daphne Bugental Presented by: Shelby Johanson, Michelle Cho

Introduction Triver’s (1974) theory of parental investment Zero-sum allocation of resources - any investment in one child means less investment in other current or future offspring. Factors affecting parental investment Low prospective reproductive potential of child Low maternal resources Supported by Daly and Wilson (1984, 1988), Garbarino (1985)

Introduction

Non human examples Birds (Gottlander,1987) Primates (Nakamichi, 1986) Human evidence Parents in high poverty vs. high wealth neighborhoods Past Experiment By Beaulieu and Bugental Matched pairs, limited measures of investment

Introduction Tested which model of PI (Additive or Contingent) Contingent predicted to be stronger. Looked at attentional resources Most other studies have looked at physical resources. Depressed mothers respond to infants with low levels of attention Depressed mothers have low levels of attentional resources. Current Study

Introduction Trivers-Willard model (1973) Mothers in good condition will invest more in sons, mothers in poor condition will invest more in daughters Depression and low education marked “poor” condition Hagen (2002) Age and parity Older mothers will invest more in singleton offspring (Even if high-risk) First born vs later born Greater investment expected in later born (Rohde et al.) Additional Tests

Participants 60 mothers and children Within child abuse prevention program 56 Latino, 4 Anglo mothers (mean age=27) Kids average age; 8.56 weeks at intake, 20 months at follow up Half of children premature, half full term Groups were equivalent in other ways Methods

Measures Demographic variables Birth history Maternal depression Measure of attentional resources. Beck Depression Inventory (BDI) Parental Investment See next slide Methods

Measures of PI Motivational measure Mothers shown 12 pictures of items (approximately equal value) available on the internet. Half were mother directed, half child directed. Mothers chose the three they would prefer as gifts at a later time. Zero-Sum measure – ranking of one to three according to number of items for mom vs child Computational/perceptual measure Mothers height estimation of child Underestimation suggests mother believes child is weaker and more in need of investment. Methods

Potential confounds Maternal age, maternal education, maternal ethnicity, number of siblings, child gender, and presence of father. Shown to not have a relationship with the dependent variables. Procedure Demographic and BDI at intake PI at 18 month visit In-home Methods

Critiques Sample Limited in terms of ethnicity, education, etc. (Even if they found the variables to not be related) PI was tested considerable after BDI scores were taken Methods

Maternal education and presence of father in the home Maternal age and parity Child gender and maternal condition Child’s birth order First-born vs. later-born Results Series of regression analyses

Step 1 Covariate Differential participation in one of two home visitation programs Step 2 Independent variables Child gestational age and maternal scores on the BDI Step 3 Predicted interaction Results Hierarchical Regression Analysis

Motivational Investment Results

Computational Investment Results

Motivational Indicators of PI Benefits to the child vs. benefits to the self Depressed mothers Give benefits to full-term infants Non-depressed mothers Give benefits to preterm infants Similar findings to nonhuman research Mothers provide different resources based on characteristics of the young Discussion

Computational Indicators of PI Care giving responses Mothers with low resources (depressive) and has premature infant less protective care system Non-depressed mothers with premature infant more protective care system Discussion

Supported or not? Predictions for both Bugental and Beaulieu (2003) and Mann (1992) were supported Discussion

Evidence for the other hypotheses Differential investment Occurs in male vs. female offspring based on the mother’s condition Not significant Combined effects of maternal age and parity It was not significant once follow-up analysis was applied genders No significance in birth order Discussion

Limitations Replication is needed For observed effects Useful to include other types of PI Financial or time investment Selective investment patterns was limited Father’s low involvement in child care Constraints Age limitations Discussion

Conclusion “If: Then” decision-making model Good response from parents to their offspring Parental decisions are contingent on complex computations Similarity in the investment pattern by both nonhuman and humans Shared evolutionary influences Discussion

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