1 PSYCHOLOGICAL SCIENCE, in press Copyright © American Psychological Society TALIS PATER, TALIS FILIUS: PERCEIVED RESEMBLANCE AND THE BELIEF IN GENETIC RELATEDNESS Paola Bressan and Maria F. Dal Martello Dipartimento di Psicologia Generale, Università di Padova, Italy Abstract—We hardly ever realize that our belief in our high rate of success in detecting family resemblances is affected by our knowledge of the actual genetic link between individuals. In the three studies reported here, 100 men and 100 women were requested to estimate the facial resemblance of photographically portrayed child/adult pairs, while being given either truthful or deceitful information, or none, about their relatedness. Believing that the members of a pair were parent and offspring was the main predictor of the perceived similarity between them. Men and women showed identical response patterns, but men gave higher ratings to pairs where the adult was allegedly a father. More than from a conscious desire to please or reassure the parents, common remarks on family resemblance appear thus to ensue from general hypothesis-testing biases in human reasoning, made perhaps more specific in men by a concern with the problem of uncertain paternity. Mothers and fathers are often told that their children look just like them. Comments on how much a newborn resembles either parent can be the prime topic of conversation, and one that tends to create considerable interest in all those present. Yet, accuracy in discriminating related from unrelated couples of adult and child has been shown to be only slightly higher than chance, regardless of the age of the child – from 6 months to 18 years (Nesse, Silverman, & Bortz, 1990). When asked to rate the resemblance between a child and three possible mothers or fathers, one of whom was the actual parent, people performed even worse; in general, children were judged no more similar to their parents than to random adults (Christenfeld & Hill,