灰姑娘效應

The Cinderella effect is a term used by psychologists to describe the high incidence of stepchildren being physically abused, sexually abused, neglected or murdered, or otherwise mistreated at the hands of their stepparents at significantly higher rates than their genetic counterparts. It takes its name from the fairytale character Cinderella, who in the story was cruelly mistreated by her stepmother and stepsisters.

Research

In the early 1970s, a theory arose on the connection between stepparents and child maltreatment. "In 1973, forensic psychiatrist P. D. Scott had summarized information on a sample of 'fatal battered-baby cases’ perpetrated in anger (…) fifteen of the twenty-nine killers – fifty-two per cent – 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.

• Years of research have confirmed the hypothesis that stepchildren are significantly more likely to be abused in terms "from baby batterings to sexual molestation of older children" to murder.

• 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".

• For over 30 years, data has been collected regarding the validity of the Cinderella effect with all the evidence proving 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

• In addition to displaying higher rates of negative behaviors (e.g. abuse) towards stepchildren, stepparents display fewer positive behaviors towards 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.

• The most powerful evidence in support of the Cinderella effect is the proof that when abusive parents have both step- and genetic children, they generally spare their own children. In such families, stepchildren were exclusively targeted 9 out of 10 times in one study and in 19 of 22 in another.

• This discrimination towards stepchildren is unusual 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." The Cinderella effect explains this discrimination of abuse among stepchildren.

Daly and Wilson

The most profound data on the idea of stepchild mistreatment has been collected and interpreted by psychologists Martin Daly and Margo Wilson, who study with an emphasis in Neuroscience and Behavior at McMaster University. Their first measure of the validity of the Cinderella effect was based on data from the American Humane Association (AHA), an archive of child abuse reports in the United States holding over twenty thousand reports.

• These records led Wilson and Daly to conclude that "a child under three years of age who lived with one genetic parent and one stepparent in the United States in 1976 was about seven times more likely (…) to become a validated child-abuse case in the records than one who dwelt with two genetic parents."

• Overall, their findings demonstrate that children residing with stepparents had a higher risk of abuse even when socio-economic factors were considered.

Explanations

参见：Infanticide (zoology)

The Cinderella effect may be best explained through evolutionary psychology. Its origin and evolution into the role of human behavior is a direct effect of the Darwinian theory of natural selection as explained by Daly and Wilson. According to theory, "research concerning animal social behaviour provide a rationale for expecting parents to be discriminative in their care and affection, and more specifically, to discriminate in favour of their own young". Natural selection measures an organism's success by its reproductive ability, explaining why parents invest their resources in their genetic children. This evolved rationale is why parents have developed the desire to protect their own young for investment in their own fitness and to ensure "genetic posterity (inclusive fitness)".

All organisms face trade-offs as to how to invest their time, energy, risk, and other resources, and investment in one domain (e.g. parental investment) generally takes away from their ability to invest in other domains (e.g. mating effort, growth, or investment in other offspring). Investment in non-genetic children reduces an individual's ability to invest in itself or its genetic children, without directly bringing reproductive benefits (except as mating effort towards the genetic parent), so evolutionary biologists would not expect organisms to regularly and deliberately care for unrelated offspring.

One would therefore expect greater parental responsiveness towards one's own offspring than towards unrelated children, and this will result in more positive outcomes and fewer negative outcomes towards one's own children than towards other children in which one is expected to invest (i.e. stepchildren). "If child abuse is a behavioral response influenced by natural selection, then it is more likely to occur when there are reduced inclusive fitness payoffs owing to uncertain or low relatedness." Owing to these adaptations from natural selection, child abuse is more likely to be committed by stepparents than genetic parents – both are expected to invest heavily in the children, but genetic parents will have greater child-specific parental love that promotes positive caretaking and inhibits maltreatment.

It is sometimes argued that this evolutionary psychological account does not explain why the majority of stepparents do not abuse their partners' children, or why a significant minority of genetic parents do abuse their own offspring. However, their argument is based on a misunderstanding: the evolutionary psychological account is that (all else equal) parents will love their own children more than other people's children – it does not argue that stepparents will "want" to abuse their partner's children, or that genetic parenthood is absolute proof against abuse. Under this account, stepparental care is seen as "mating effort" towards the genetic parent, such that most interactions between stepparent and stepchildren will be generally positive or at least neutral, just usually not as positive as interactions between the genetic parent and the child would be.

Critical studies

Since the introduction of the theory of the Cinderella effect, many psychologists have criticized and collected information, intending to refute the claim that stepparents and abuse in children are directly related. In one such study, John Harrop administered a survey by telephone, asking participants "whether they had 'slapped’ certain family members (considered one by one) within the last year, had 'punched’ them, and had 'used a knife or gun on’ them and so forth, when they had a disagreement or were angry with them’." The survey revealed that "the 117 stepparents who did not hang up (…) were no more likely to profess that they had assaulted the children under their care than were genetic parents",.

Alternative explanations

There are many skeptics who disregard the Cinderella effect, convinced that step-relationships are not a direct cause of elevated abuse among children.

• One alternative explanation is that "a high incidence of abusive stepfamilies could, in principle, be a spurious result of biased detection or reporting." Evidence against this shows that when higher criteria is required in the analysis of records, the risk for stepparents to be the perpetrators increases, contrary to skeptics' beliefs. Furthermore, victim's reports (which depend only upon victims rather than on official reports and detection) show higher rates of abuse by stepfathers than by genetic fathers.

• Others say that economic backgrounds could be an underlying cause and "one might hypothesize that the stress of poverty cause the poor to be especially likely to abuse and kill their children and also to experience high rates of divorce and remarriage, making steprelationship (sic) an incidental correlate of abuse." Although studies show that poverty increases the chances of child abuse, further analysis shows it has little connection to step-relationships.

• Another explanation has been that stepfathers will treat all possessions of the mother worse than they would in other circumstances. A stepfather might be more abusive to the pets and furniture of the new family as well as his stepchildren.

See also

• Parenting
• Family
• Paternal bond
• Maternal bond
• Nuclear family
• Cinderella complex
• The WAVE Trust

References

• Burgess, Robert L.; Alicia A. Drais. Beyond the "Cinderella Effect: Life History Theory and Child Maltreatment. Human Nature (New York: Springer). 1999, 10 (4): 373–95. doi:10.1007/s12110-999-1008-7. 
• Daly, Martin; Margo Wilson. An Assessment of Some Proposed Exceptions to the Phenomenon of Nepotistic Discrimination Against Stepchildren (PDF). Annales Zoological Fennici (Helsinki: Finnish Zoological and Botanical Publishing Board). September 10, 2001, 38 (3–4): 287–96. ISSN 0003-455X. 
• Daly, Martin; Margo Wilson. The Truth About Cinderella: a Darwinian View of Parental Love. New Haven: Yale University Press. 1998. ISBN 0300080298. 
• Daly, Martin; Margo Wilson. Violence Against Stepchildren (PDF). Current Directions in Psychological Science (Association for Psychological Science). 1996, 5 (3): 77–81. doi:10.1111/1467-8721.ep10772793. 
• Gelles, Richard J.; John W. Harrop. The Risk of Abusive Violence Among Children with Nongenetic Caretakers. Family Relations (National Council on Family Relations). 1991, 40 (1): 78–83. doi:10.2307/585662.