Nature vs. Nurture

The Impact on Children Adopted from Foster Care


  • What determines the behavior, academic ability and future actions of children?
  • How much of their personality, morals and ethics are predetermined by their genetic make-up?
  • Can the power of a nurturing environment and the love of an adoptive family overcome any potentially negative predisposition?

I will answer all of these questions and hopefully provide you with plenty of information and research based evidence to allow you to determine for yourself how you feel about the Nature vs. Nurture debate in reference to children who have been adopted from foster care.

Genetic Predispositon/Nature

While we may think that all of our personality and intellectual traits are determined by our genetic make-up Collins, Maccoby, Steinberg, Hetherington and Bornstein (2000) report that heredity rarely even accounts for 50% of any given persons personal characteristics. Height is a characteristic that is typically determined by genetics, whereas behaviors are more typically influenced by environmental factors. With that being said, Collins (2000) goes on to describe the fact that heredity can play a role in a persons predisposition to be prone to certain behavioral characteristics, such as anti-social behavior.

Butcher and Plomin (2008), Fisch, Bilek, Deinard and Chang (1976), and McGue, Keyes, Sharma, Elkins, Legrand, Johnson and Iacono (2007) all agree in their findings that the IQ of a child that is adopted from foster care does not change regardless of the amount of nurturing the child receives and/or the environment in which they are adopted into.

Plomin, Fulker, Corley and DrFries (1997) followed 245 biological mothers through their pregnancy and then followed the children as they were adopted and found that the influence of nature, or heredity, seemed to increase for the adopted children as they moved into the adolescent and young adult phases of their lives. This seems to point to a conclusion that the environment that a child is adopted into has little effect on later cognitive development. Following this research, Loehlin, Horn and Ernst (2007) followed up with children who had been adopted 30 years previously and the responses from those now adult reflected that they felt like they have less satisfactory outcomes in their adult lives than their siblings that were biological offspring to their adoptive parents.

Environmental Effects/Nurturing

One of the most significant statements that was reported in the research that I studied was the fact that "adoption is a positive intervention for children's cognitive development" (Waterman, Nadeem, Paczkowski, Foster, Lavner, Belin and Miranda, 2013). This statement was followed by the suggestion that the quality of the environment was also a significant predictor of the academic outcomes for chidlren adopted from foster care. van IJzendoorn, Juffer, and Klein Poelhuis (2005) also find that adoption has increased cognitive development in foster children and can lead to extensive congitive recovery. van IJzendoorn (2005) also go on to report that children adopted from foster care do significantly better academically and have superior cognitive development when compared to their non-adopted siblings.

Environmental Factors

Leahy (1935) suggests that one of the main benefits of the adoptive environment may be the increased IQ of adoptive parents over that of the biological mother. When looking at the research, the average IQ of the biological mothers is reported as 106.65 while the average IQ of the adoptive parents was 113.45 (Horn, Loehlin, and Willerman, 1978).

When McGue (2007) looked at the environmental effects on adopted children they concluded that 20-30% of the difference between adopted children's cognitive performance and that of their siblings or peers still in foster care. McGue also includes in his research the fact that the adoptive parents of children from foster care had higher education than the biological parents, less alcohol dependency, and a significantly decreased if not non-existent exposure or dependency to illegal substances.

Horn, Loehlin, and Willerman (1978) suggest that adoptive parents may have been more favored environmentally than the biological mothers of the adopted children who may have experienced a less favorable environmental upbringing or current experience.

While the behavioral actions of adopted children is not based on their genetics, the adoptive parents response to their behaviors may play a huge role in the determination of their future behaviors. Collins (2000) finds that behaviors that are exhibited by infants, and the subsequent response by the parents to the specific behavior are a much stronger predictor of future behavior than heredity.

Research Studies & Results

Waterman (2013) contradicts the research of Butcher (2008), Fisch (1976) and McGue (2007) by reporting that children tested prior to adoption (between 4 and 6 years of age) had an average IQ of 86; when re-assessed in adolescence the same children all showed increased IQ scores and higher academic achievement than their non-adopted peers. Children who remained in foster care into adolescence showed lower cognitive scores while the children who were adopted increased from their initial average score of 88.36 to an average score of 107, 60 months post-adoption.
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When a group of 144 adopted children were assessed using the Wechsler Intelligence Scale for Children (WISC), and the Wide Range Achievement Test (WRAT) their scores were compared with 288 non-adopted children in a study performed by Fisch (1976). Fisch reports that the adopted children scored better on the section of the WISC which assesses abstract reasoning and they also scored higher in the spelling and reading sections of the WRAT which leads to a conclusion that they have higher academic achievement than their non-adopted peers.

There was no significant difference in the IQ scores of the two groups of students (adopted vs. non-adopted), yet the adopted children displayed superior cognitive performance.
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van den Dries, Juffer, van IJzendoorn, and Bakermans-Kranenburg (2010) document the fact that foster children who have been adopted have higher cognitive skills than children who are adopted from an institutionalized facility. The adopted foster children also have superior motor skills.
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300 adoptive families who had adopted a child from foster care and also had a biological child of their own were studied by Horn (1978) and the results show that there was little to no difference between the IQ's of the adopted and biological children which led Horn (1978) to conclude that IQ is not hereditary. This same group of 300 adopted children were contacted 30 years after the initial study and asked to complete a questionnaire. 133 of the adopted children returned the questionnaire and the information that was gained from their replies found that the majority of the adopted children felt that the biological children in their adopted families were seen by their parents as being better students and less trouble. The biological children also had a higher level of education, more friends, participated in more social activities, were more independent and had more stable employment than their adopted siblings. The adopted children felt that they were not as close with their parents and felt that they were more anxious or depressed than their non-adopted siblings.


It is clear to me that there may never be a clear cut answer to the debate of nature versus nurture that is 100% for or against either side. This conclusion is difficult to reach, in part because of the vast number of variables and manners if testing to collect data. Based on the data that I compiled from the articles that I read, I have a much better understanding of the potential for heredity to play at least some small role in the future of children adopted from foster care. The findings of Plomin (1997) suggest that around the adolescent years there may be some characteristics that can only be explained through heredity. However, the vast amount of research that supports increased cognitive development, performance and superior reasoning lead me to believe that all of these factors will override the minor behaviors that may be inherently present in an adopted child's personality. In the coming years I hope that I can support this conclusion with real life facts as I look forward to seeing how nature versus nurture plays out for my daughter who is soon to be adopted from foster care.
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June Allison

I am the Mom to 5 beautiful daughters ages 15, 12, 11, 7 and 3. My husband and I are also foster parents to our 15 and 3 year old daughters. We have had our 3 year old daughter since she was 3 months old. I am extremely interested in the age-old debate of Nature vs. Nurture, especially since we are in the process of finalizing our adoption of our 3 year old foster daughter. I know her genetic background, and it was less than ideal. How much of a role will this play on her behaviors, academic success and her future as an adult?


  • Butcher, L., Plomin, R. (2008). The Nature of Nurture: A Genomewide Association Scan for Family Chaos. National Center for Biotechnology Information, 38, 361-371.
  • Collins, W., Maccoby, E., Steinberg, L., Hetherington, E., Bornstein, M. (2000). Contemporary Research on Parenting: The Case for Nature and Nurture. American Psychologist, 55, 2, 218-228.
  • Fisch, R., Bilek, M., Deinard, A., Chang, P. (1976). Growth, Behavioral, and Psychologic Measurements of Adopted Children: The Influences of Genetic and Socioeconomic Factors in a Prospective Study. Behavioral Pediatrics, 89,3, 494-500.
  • Horn, J., Loehlin, J., Willerman, L. (1978). Intellectual Resemblance Among Adoptive and Biological Relatives: The Texas Adoption Project. Behavior Genetics, 9, 3, 177-205.
  • Leahy, A. (1935) A Study of Adopted Children as a Method of Investigating Nature-Nurture. Journal of the American Statistical Association, 30, 189, 281-287.
  • Loehlin, J., Horn, J., Ernst, J. (2007). Genetic and Environmental Influences on Adult Life Outcomes: Evidence from the Texas Adoption Project. Behavior Genetics, 37, 463-476.
  • McGue, M., Keyes, M., Sharma, A., Elkins, I., Legrand, L., Johnson, W., Iacono, W. (2007). The Environments of Adopted and Non-adopted Youth: Evidence on Range Restriction From the Sibling Interaction and Behavior Study. Behavior Genetics, 37, 449-462.
  • Plomin, R., Fulker, D., Corley, R., DeFries, J. (1997). Nature, Nurture and Cognitive Development from 1 to 16 Years: A Parent-Offspring Adoption Study. Association for Psychological Science, 8, 6, 442-447.
  • van Den Dries, L., Juffer, F., van IJzendoorn, M., Bakermans-Kranenburg, M. (2010). Infants’ Physical and Cognitive Development After International Adoption From Foster Care or Institutions in China. Journal of Developmental & behavioral Pediatrics, 31, 144-150.
  • van IJzandoorn, M., Juffer, F., Klein Poelhuis, C. (2005). Adoption and Cognitive Development: A Meta-Analytic Comparison of Adopted and Nonadopted Children's IQ and School Performance. Psychological Bulletin, 131, 2, 301-316.
  • Waterman, J., Nadeem, E., Paczkowski, E., Foster, J., Lavner, J., Belin, T., Miranda, J. (2013). Pre-Placement Risk and Longitudinal Cognitive Development for Children Adopted from Foster Care. Child Welfare, 92, 4, 9-30.