Self-referent phenotype matching: theoretical considerations and empiricalevidence

In most birds and mammals, young are raised in family groups. The phenotype s of nestmates and parents are thus reliable cues for recognition of conspe cifics and kin. However, in some species, young develop alone, or in broods of mixed relatedness (e.g. because of multiple paternity or maternity), or among heterospecifics or unrelated conspecifics (brood parasites). Under t hese circumstances, the best referent (model) for discriminating close from distant kin and heterospecifics from conspecifics might be one's own self. This recognition process is known as self-referent phenotype matching. Her e we review recent experimental evidence of self-referencing and suggest th at behavioral neuroscience can provide new tools and insights into how it w orks (its proximate mechanistic and ontogenetic bases) and why it exists (i ts adaptive significance).