The neuropeptides oxytocin and vasopressin are evolutionarily conserved regulators of social perception and behavior. Evidence is building that they are critically involved in the development of social recognition skills within rodent species, primates, and humans. We investigated whether common polymorphisms in the genes encoding the oxytocin and vasopressin 1a receptors influence social memory for faces. Our sample comprised 198 families, from the United Kingdom and Finland, in whom a single child had been diagnosed with high-functioning autism. Previous research has shown that impaired social perception, characteristic of autism, extends to the first-degree relatives of autistic individuals, implying heritable risk. Assessments of face recognition memory, discrimination of facial emotions, and direction of gaze detection were standardized for age (7-60 y) and sex. A common SNP in the oxytocin receptor (rs237887) was strongly associated with recognition memory in combined probands, parents, and siblings after correction for multiple comparisons. Homozygotes for the ancestral A allele had impairments in the range −0.6 to −1.15 SD scores, irrespective of their diagnostic status. Our findings imply that a critical role for the oxytocin system in social recognition has been conserved across perceptual boundaries through evolution, from olfaction in rodents to visual memory in humans.A n ability to recognize individuals from the same species is a vital component of social cognitive development in both humans and other animals that live in social groups. Social memory allows the recognition of conspecifics, hence ascription of a specific identity to another individual. In turn, this permits inferences to be made about their personal characteristics and the recollection of previous encounters, thus guiding appropriate current social responses. The ability to form social memories underpins pair-bonding (1) and bonding with offspring (2). In rodents, as well as many other species, the primary cues used in this recognition process are olfactory or pheromonal, but in primates visual and auditory processes are of paramount importance. Evidence is building that the neuropeptides oxytocin and arginine-vasopressin are critically involved in the development of social recognition in rodent species (3-6), primates (7), and humans (8-11).Thus, there are conserved mammalian mechanisms by which the neuropeptides oxytocin and vasopressin influence social recognition processes in both males and females, especially recognition memory. Evidence comes from a wide range of studies over the past two decades. Could polymorphisms in genes coding for these molecules, or for their receptors, be relevant to individual differences in social perception? Social cognitive skills are highly heritable in the general population (12, 13), implying that individual differences in social cognition may be strongly influenced by corresponding individual differences in gene expression. The social implications of allelic variation in the oxytocin receptor (...