The Cinderella Effect: Evolutionarily Inclined Abusive Stepparents

I’m sure we are all familiar with the story of Cinderella. Orphaned girl mistreated by her new family, abused by her evil stepmother and stepsisters… But it’s just a fairy tale, right?

What if I told you that steprelationships have higher incidences of child-abuse and mistreatment when compared to genetic parent-child relationships?

This differential mistreatment is referred to as the Cinderella Effect.

This phenomenon was coined in the 1970’s by Dr. P. D. Scott, a forensic psychiatrist, after he researched a sample of “fatal battered-baby cases” that were perpetrated in anger and found that over 50% of the killers, (15 out of 29) were actually the child’s stepfather.

Wilson et al. (1980) analyzed child abuse data from an archive collating mandated reports from jurisdictions representing about half the U.S. population at the time and found that in 1976, 279 cases of “fatal physical abuse” involved 43% of the victims and their stepparents; this data, when combined with population-at-large estimates, can suggest estimates that stepchildren incurred fatal deaths resulting from abuse at about 100 times the rate for children of the same age living with both biological parents.

In Canada, data in national archives of all reported homicides indicate that children under 5 years of age were beaten to death by their putative genetic fathers at a rate of 2.6 deaths per million child-years at risk (residing with their fathers) in 1974-1990, while the corresponding rate for stepfathers was over 120 times greater at 321.6 deaths per million child-years at risk (Daly & Wilson 2001).

In non-fatal cases when abusive parents have both genetic and step children in the household, the parents, male and female, tend to spare their genetic children and target stepchildren on an average of 9 out of 10 cases of abuse (Daly & Wilson) and 19 out of 22 in another studies.

Additionally, the highest majority of abuse (fatal or not) by a stepparent has been reported as the genetic mother’s live-in boyfriend or a stepfather; the higher rate is most likely correlated with statistics that show that most children of divorced or separated families reside with their mothers, rather than their fathers.

So– enough with the gruesome statistics.
What causes this trend of increased domestic violence towards non-biological children? And why are the biological children, like the stepsisters in Cinderella, selectively spared from the abuse (in most cases)?

Evolutionary psychologists suggest these behaviors to be remnants of an adaptive reproductive strategy in primates. Stepparental care is not unique to human beings: it exists in the animal kingdom as well. Frequently, male primates would kill the offspring of other males in order to bring their mothers into estrus (“in heat”, or sexually receptive) and increase chances of reproduction.

Similarly, investing resources in a new mate’s offspring, while fully aware that the offspring are from a prior union, is part of the effort to mate in species in which established couples stay together for longer than just one breeding season.  Stepparenting these offspring can be seen as “adaptive” behavior; however, the acceptance of caring for nonbiological offspring does not imply that the offspring receive as much love, care, and value from the stepparent.

Assuming the role of stepparent may be a tolerable price to pay to acquire a desired mate, but how much one should then invest in stepchildren remains negotiable. Evolutionarily, biological children would be signs of one’s reproductive fitness to the parents, leading to strong self-sacrificial love for their young– the same cannot be said for the nonbiological children.  Stepchildren receive significantly lower levels of parental investment than their genetic counterparts (the biological children), and emotional capital is lacking; offspring from a previous mating are viewed as a cost, rather than a benefit to the new caregiver.

If we look at the subject from a Personality Theory perspective, another possible explanation could be offered. Although in principle, the population of adults in stepfamilies could include disproportionate numbers of disturbed, violent or otherwise abuse-prone people, the selective sparing of the biological children in cases of abuse rule this theory out.

Some studies suggest that the way parents feel towards their children can influence how they treat them. In one such study, positive affect (feeling or emotion) was consistently felt towards biological offspring, inclining the parents to be less volatile, more positive, and expressive towards their biological children; on the other hand, stepchildren were associated with more volatile feelings and consistently negative affect states, significantly affecting their treatment of the stepchildren during disagreements and arguments.

The data also revealed that both genetic and step-parents were more likely to express positive feelings for children to whom they felt similar, which similarity provided a basis for personal synchronization.


Although the occurrence of parental abuse is higher in non-biological parents, this does not mean that all non-biological stepparents are inclined to be abusive.  Extremely negative outcomes in stepparental-child relationships do exist, but they are statistically infrequent and do not represent the majority of non-biological caregiver-child relationships.

However, it is also important to keep in mind that the story of Cinderella is not merely a fairy tale…

Anderson KG, Kaplan H, Lam D & Lancaster J (1999b) Paternal care by genetic fathers and stepfathers II: reports by Xhosa high school students. Evolution & Human Behavior 20: 433-451.

Aquilino WS (1991) Family structure and home leaving: a further specification of the relationship. Journal of Marriage & the Family 52: 405-419.

Daly & Wilson (2007) Is the “Cinderella Effect” controversial? In Crawford & Krebs (Eds) Foundations of Evolutionary Psychology, pp. 383-400. Mahwah, NJ: Erlbaum.

Giles-Sims, Jean; Finkelhor, David (1984). “Child Abuse in Stepfamilies”. Family Relations (National Council on Family Relations) 33 (3): 407–413. doi:10.2307/584711.

Lightcap JL, Kurland JA & Burgess RL (1982) Child abuse: a test of some ideas from evolutionary theory. Ethology & Sociobiology 3: 61-67.

Lucas DR, Wezner KC, Milner JS, McCanne TR, Harris IN, Monroe-Posey C & Nelson JP (2002). Victim, perpetrator, family, and incident characteristics of infant and child homicide in the US Air Force. Child Abuse & Neglect 26: 167-186.

Martin Daly, Margo Wilson (2005) The ‘Cinderella effect’ is no fairy tale, Trends in Cognitive Sciences, Volume 9, Issue 11, November 2005, Pages 507-508, ISSN 1364-6613,

Miller, M. (2004). The Cinderella effect: The psychological bases and mental dynamics of step-parental ambivalence. Florida Atlantic University.

Packer, C.; Pusey, A. E. (1983). “Adaptations of Female Lions to Infanticide by Incoming Males”. The American Naturalist 121 (5): 716. doi:10.1086/284097

Trivers, R. L. (1971). “The Evolution of Reciprocal Altruism”. The Quarterly Review of Biology 46: 35–57. doi:10.1086/406755


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