Practically every parent has been told, from time to time, that his or her child looks "just like you." But a new study concludes that this purported likeness, no matter how often commented upon by relatives or friends, is illusory in most cases.

"Children in general do not look enough like their parents for a resemblance to be detected," researchers from the University of California at San Diego report in today's issue of the journal Nature, "with the one exception that one-year-olds look like their fathers."

Psychologist Nicholas J.S. Christenfeld decided to study parent-child resemblance after being told repeatedly that his baby daughter, Emma, looked like him. Few observers, however, had said that the infant resembled his wife. Intrigued by the disparity, he set out to determine whether a disinterested stranger could perceive a likeness between children and their parents.

Advertisement

Christenfeld and assistant Emily A. Hill obtained photographs from 24 different families. Each pair of parents provided a picture of one of their children at age 1, as well as pictures of each parent as adults and as infants approximately 1 year old. In families where children were older, parents also provided pictures of their child at the ages of 10 and 20 with the infant photograph.

The researchers then recruited 122 test subjects and asked them to look at numerous sets of four pictures. Each set included one picture of a 1-year-old child and three of adult women (or men), only one of whom was the real mother (or father). The subjects were asked to match the infant's picture with the adult the child most resembled.

Subjects were also asked to choose among photos of three possible mothers or fathers to match with photos of the children at ages 10 and 20.

Advertisement

In every case but one, the subjects were unable to match the offspring with the correct parents at a rate significantly higher than 33 percent, the probability of a right answer by chance alone. But subjects were able to match accurately a 1-year-old child of either sex with the real father about 50 percent of the time -- although not with the mother.

The volunteer subjects were adept at other kinds of facial recognition tasks. For example, they were able to match a picture of a 1-year-old child with the same child at age 10 or 20 -- or to identify correctly which picture of the parent as an infant corresponded with the same parent as an adult -- between 60 percent and 80 percent of the time.

If the study's findings seem counterintuitive, Christenfeld said yesterday, "remember that it's very easy in hindsight to see a resemblance. If you look at a father and son together, you might say, Oh my God, that's right -- they have exactly the same nose.' But you're not noticing that they have different eyes, ears" and other features that might make them appear quite dissimilar to an objective third party who didn't know of the relationship.

Advertisement

Owen Rennert, chairman of pediatrics at Georgetown University Medical Center and a geneticist, said that his experience did not confirm the San Diego hypothesis.

"There are babies that I see that look like mom or dad. Then there are babies for whom I wouldn't -- unless they were arriving with a parent -- have any clue that they came from that parent."

Christenfeld and Hill theorize that the high success rate for matches between fathers and 1-year-olds indicates that "there may be an evolutionary rationale" for the resemblance. "While a mother can be quite sure that the baby is hers, no matter what it looks like, the father cannot. It could then be to a baby's advantage to look like the father to encourage paternal investment." Over many generations, babies who most resembled their fathers ostensibly would have received more resources from those fathers, thus increasing the children's chances of living to be old enough to reproduce and pass on the paternal-resemblance trait or traits.

Advertisement

Rennert was not impressed by that argument. Because the degree of likeness between offspring and parents depends on a large number of genetic and environmental factors, attributing the resemblance to some kind of genetic bias is "really stretching it," he said.

Whatever the merit of that thesis, acquaintances do appear motivated to point out presumptive similarities between parents and children. The San Diego authors speculate that it "could be due to a desire to please the parents." Or maybe they are responding to "characteristics that still pictures cannot capture."

ncG1vNJzZmivp6x7uK3SoaCnn6Sku7G70q1lnKedZK6zr8eirZ5noKS5qsDInKpoaWlugnB9kWhobWeUpHqktMilm6udnmLCtMHApaOyZZykvKx5y6KinmWknbKqvoypmKudnqnAbr%2FTrpuyZaOWxrR5zahmcJ1harKirsFmcHBuZmKBp7HAZnBpcWdisXeAlW1qcGtgZ36mew%3D%3D