Kin recognition is animals' abilities to distinguish between close genetic kin and non-kin. In evolutionary biology and in psychology

Psychology

Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

, such capabilities are presumed to have evolved to serve the adaptive functions of kin altruism (see kin selection

Kin selection

Kin selection refers to apparent strategies in evolution that favor the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction. Charles Darwin was the first to discuss the concept of group/kin selection...

) and inbreeding

Inbreeding

Inbreeding is the reproduction from the mating of two genetically related parents. Inbreeding results in increased homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits. This generally leads to a decreased fitness of a population, which is...

 avoidance. Apart from a few exceptional cases, such as the green-beard effect

Green-beard effect

The gene-centered view of evolution postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication...

, kin recognition is achieved via several cue-based mechanisms, such as imprinting

Imprinting (psychology)

Imprinting is the term used in psychology and ethology to describe any kind of phase-sensitive learning that is rapid and apparently independent of the consequences of behavior...

 and phenotype matching. Because kin recognition is cue-based, errors sometimes occur. A well known example is the Westermarck effect

Westermarck effect

The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction. This phenomenon was first hypothesized by Finnish...

in which unrelated individuals who spend their childhood in the same household find each other sexually unattractive.