Effects of rearing conditions on early visual development in common marmosets.

Early development of visual behavior was examined in hand-reared (HR) and parentally reared (PR) common marmosets (Callithrix jacchus). On the day of birth, most of the marmosets exhibited sensitivity to light and sound: they closed their eyes in response to light and oriented to the sound sources. The behavior of tracking moving visual stimuli was exhibited at around 10 days postnatally in PR marmosets, but the onset of this behavior was delayed to the age of 16 days in HR marmosets. The delay occurred possibly because of the poor input of optical flow under the HR environment. The onset age of head-cocking was about 2 weeks in both groups of marmosets, and the HR marmosets began head-cocking and visual tracking simultaneously. Both groups of marmosets exhibited sensitivity to optical approach at the age of around 30 days: the age to wean and increase independent locomotion. The results suggested that the onset of motion perception preceded detailed shape and depth perception in marmosets, and the developmental sequence in marmosets was similar to those in humans and macaque monkeys. Marmosets appear to be useful animal models to examine environmental effects on early visual development.