Cinderella, the well-known fairy tale by the Brothers Grimm, tells a story of a rich man who remarried after his wife died. His biological daughter is oppressed by her new stepmother, all while she favours her own biological daughters. They treat her as a “kitchen maid”, did everything imaginable to hurt her, and called her “Cinderella” because she always looked dusty and dirty.

It is a story that has been told and retold many times in popular culture. Some have called this an unfortunate “stereotype” of stepparents.

On the other hand, evolutionary psychologists (and married couple) Martin Daly and Margo Wilson argue that the trend is real. They have popularised the term, the “Cinderella effect”, referring to the tragic phenomenon where children have a higher risk of abuse by non-biological parents – whether married to the child’s parent or not.

The “Cinderella Effect”

In Daly and Wilson’s 1998 book, “The Truth about Cinderella: A Darwinian View of Parental Love”, they make the case that an American child is one hundred times more likely to be abused or killed by a stepparent than by a genetic parent.

On the other hand, they note, “abusive stepparents seldom harm their own children”.

Drawing from Canadian data in a 2001 article, they further argue that risk is not limited to “mother’s boyfriends” but applies to stepfathers as well. Both groups have a higher risk of fatal child abuse of children under five years of age, as compared to genetic fathers (whether married or cohabiting with the mothers in de facto marriages):

Numbers and rates at which Canadian children under five years of age were beaten to death 

More recently, a 2022 article published in the Journal of Criminal Justice partly supported and challenged these conclusions, suggesting that unmarried partners – but not stepparents – are significantly more likely to seriously injure the child as compared to biological parents.

The authors of the study – Block and Kaplan – had recognised that the body of research “consistently found that children in stepfamilies have a significant increased risk of being physically abused or killed compared to children in families with only biological parents”. However, they took the view that previous results were affected by reporting bias, arguing that older results were skewed because a man who hits his biological child is less likely to be reported than a man who hits his girlfriend’s child.

Why the “Cinderella Effect”?

While the “Cinderella effect” is well-documented, there is a highly controversial debate over the question: Why?

Draw from their field of evolutionary psychology, Daly and Wilson have suggested that the reason lies in the genetic connection between biological parents and children. In their view, humans evolved to be “nepotistic”, engaging in actions that contribute to the survival and reproductive success of those who are genetically related. As a result, they favour their own biological children.

On the other hand, they explain the “kindly deportment” of most stepparents mainly in the context of reciprocity with the genetic parent. On this view, for example, a stepfather would love his stepchildren essentially as a gesture of love towards their mother.

There are alternative theories, as proposed by Giles-Sims and Finkelhor, which may not be mutually exclusive. Weaker normative taboos against incest have been suggested to explain why stepparents may sexually abuse or assault non-biologically related children. Other explanations for abuse include higher stress levels among stepfamilies, lack of resources (e.g. economic resources or parenting skills) or that people forming stepfamilies may be more violence-prone or have other emotional challenges.

Although Giles-Sims and Finkelhor have noted that “no one factor or set of factors may be sufficient to explain child abuse in stepfamilies”, we should be mindful that one’s perspective on the reasons for abuse would shape attitudes and approaches towards intervention efforts.

For example, if we think that the key reason is lack of resources, then we are likely to concentrate efforts towards providing blended families with various resources in order to better support them.

This appears to be the view of the Singapore Children’s Society in a July 2024 research brief, which made certain recommendations in light of “the absence of tailored resources and lack of support for stepfamilies, particularly for step-children”. It thus called for the establishment of “step-family friendly schools” and a “centralised resource centre for step-families”.

Keeping in Mind the Challenges and Complexities

As with any area of social science research, these studies show trends and tendencies. We should not interpret them simplistically to stereotype all stepparents.

Not all stepparents are abusive; there are many unseen and unheard stepparents who are doing their very best to care for children who are unrelated.

On the other hand, it is also obvious that not all biological parents are benevolent. In Singapore, we have heard cases of biological parents who have abused and killed their own children too.

However, the data on the “Cinderella effect” should also lead us to be mindful of the unique and specific challenges and complexities faced by stepfamilies, especially the risks posed by a mother’s unmarried partner.

It might also be useful to guide law enforcement and child protection services, as well as caregivers or loved ones, to pay special attention to certain risk factors in preventing and addressing child abuse.

For example, could we encourage women to be more mindful of certain “red flags” (e.g. drug abuse, violent tendencies, ill-treatment of children) in their relationships and to put an end to such relationships? Should the authorities increase their supervision of children in such risky situations?

How can we build stronger marriage and families, as an upstream intervention?

These are all important conversations to have, in the interests of protecting children both today and in the future.