Spatial-frequency discrimination in cats.

Spatial-frequency discrimination thresholds were measured in two cats by using a two-alternative forced-choice procedure. A range of standard spatial frequencies centered around the peak of the cat's contrast-sensitivity function was sampled. For comparison, discrimination thresholds were also measured in two human observers at spatial frequencies centered around the peak of the human contrast-sensitivity function. For the humans, spatial-frequency discrimination thresholds averaged 4%, while for cats discrimination thresholds averaged 50%. The relatively poorer performance of the cats cannot be entirely explained on the basis of the larger sample spacing of the feline retinal mosaic. More accurate predictions can be obtained from a model that assumes that the cat bases its discrimination performance on the level of activity within that mechanism maximally activated by the standard spatial frequency.