Spatial acuity of the chicken.

Visual acuity was measured by determining the highest spatial acuity at which chickens aged 1-25 days jumped consistently to a physically supported grating instead of to an unsupported homogeneous field. In contrast to the gradual visual development found for kittens, monkeys, and humans, the chicken exhibits asymptotic sensitivity to spatial detail (with acuity at about 1.5 c/deg) within 48 h of hatching.