Cinderella effect

In evolutionary psychology, the Cinderella effect is the alleged higher incidence of different forms of child-abuse and mistreatment by stepparents than by biological parents. It takes its name from the fairy tale character Cinderella. Evolutionary psychologists describe the effect as a remnant of an adaptive reproductive strategy among primates in which males frequently kill the offspring of other males in order to bring their mothers into estrus, and give the male a chance to fertilize her himself. There is both supporting evidence for this theory and criticism against it.

In the early 1970s, a theory arose on the connection between stepparents and child maltreatment. "In 1973, forensic psychiatrist P. D. Scott summarized information on a sample of "fatal battered-baby cases" perpetrated in anger (…) 15 of the 29 killers – 52% – were stepfathers." Although initially there was no analysis of this raw data, empirical evidence has since been collected on what is now called the Cinderella effect through official records, reports, and census.

For over 30 years, data has been collected regarding the validity of the Cinderella effect, with a wealth of evidence indicating a direct relationship between step-relationships and abuse. This evidence of child abuse and homicide comes from a variety of sources including official reports of child abuse, clinical data, victim reports, and official homicide data. Studies have concluded that "stepchildren in Canada, Great Britain, and the United States indeed incur greatly elevated risk of child maltreatment of various sorts, especially lethal beatings".

Powerful evidence in support of the Cinderella effect comes from the finding that when abusive parents have both step and genetic children, they generally spare their genetic children. In such families, stepchildren were exclusively targeted 9 out of 10 times in one study and in 19 of 22 in another. In addition to displaying higher rates of negative behaviors (e.g., abuse) toward stepchildren, stepparents display fewer positive behaviors toward stepchildren than do the genetic parents. For example, on average, stepparents invest less in education, play with stepchildren less, take stepchildren to the doctor less, etc. This discrimination against stepchildren is unusual compared with abuse statistics involving the overall population given "the following additional facts: (1) when child abuse is detected, it is often found that all the children in the home have been victimized; and (2) stepchildren are almost always the eldest children in the home, whereas the general (…) tendency in families of uniform parentage is for the youngest to be most frequent victims."

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