Visual acuity was measured with a grating test object in which alternating bars were matched in brightness but differed in wavelength. If the wavelength difference between adjacent bars was great enough, acuity scores were obtained which were as high as those obtained with test objects in which there was a large brightness difference between adjacent bars.

Six tree squirrels were tested on a series of color discrimination problems utilizing various combinations of nine color filters ranging from 680 to 420 mu with intensity randomized. All animals reached criterion for all combinations by the 10th day of testing. These data support studies using indirect methods in demonstrating that tree squirrels possess color discrimination ability.