A simultaneous two-choice test was used to investigate discrimination between a familiar (F) and an unfamiliar conspecific (U) in Japanese quail, selected for high (HSR) or low (LSR) social reinstatement behavior (tendency to rejoin and stay close to conspecifics). Animals were 1-week unsexed and 6-week-old male quail. One-week-old LSR quail and 6-week-old male HSR quail displayed discrimination after 24 hr of pair contact (P < 0.05), and a tendency to discriminate (p < 0.10) was found in adult male LSR quail. After I week of pair contact, results were similar in LSR quail chicks, but no discrimination was evidenced in adult quail of either line. Therefore, Japanese quail are able to discriminate between a familiar cagemate and an unfamiliar conspecific after only 24 hr of pair contact. Moreover this study reveals for the first time in this species that social motivation and age both influence the display of individual discrimination. (C) 2009 Wiley Periodicals, Inc. Dev Psychobiol 51: 311-321, 2009.