Contrary to both popular culture tales like Cinderella and the tenants of evolutionary theory, a parent is not likely to favor his or her biological offspring to an adopted child, according to new research published online recently in the journal Evolution and Human Behavior.
While parents did rate their adoptive children higher in negative traits such as arrogance, both biological and adopted youngsters were rated similarity in terms of positive characteristics such as conscientiousness and persistence, Science reported in an article Monday.
The findings are based on a comparative analysis of 135 pairs of “virtual twins” (or siblings that are approximately the same age and consist of either one adopted child and one biological one or two adopted children) and were led by California State University psychologist Nancy Segal.
Findings contradict Kin Selection Theory
As Segal and her colleagues explained in their study, the theory of Kin Selection suggests that a parent will act more favorably to their biological children than their unrelated children in order to ensure the reproductive success and ensure the propagation of their own genetic line.
“By extension, it may be argued that parents should also have less favorable perceptions of the intellectual, personality, and other behavioral traits of unrelated children, compared with biologically related children,” the authors wrote. They noted, “Consistent with prior research, the IQ scores of the biological children exceeded those of the adopted children.”
“A between-pair analysis revealed no difference between biological children and members of adopted–adopted pairs in ratings of favorable or unfavorable traits,” they added. “More telling within-family comparisons of adopted-biological pairs revealed higher scores for adoptees on unfavorable traits, consistent with Kin Selection Theory, but no differences between adoptive and biological children on favorable traits, consistent with the compensatory model.”
Segal’s team said that their findings refine the overall understanding of how parents deal with both genetically related and non-biological offspring. According to Science, the results are reflective of the modern-day ease of adopting children and the creation of conditions in which a person’s strong desire to parent overrides kin selection behaviors.