The what and the where of the pigeon's processing of complex visual stimuli.

Eight pigeons were trained on a go-no go visual discrimination involving 1 S+ and 15 S- s. The 16 discriminative stimuli were black-and-white line drawings created by the factorial combination of 4 different geometric shapes (wedge, cylinder, cone, handle) in 4 different spatial locations (right, left, above, below) in relation to a common shape (cube). All of the pigeons readily learned this complex visual discrimination. Each bird's pecking behavior was controlled by both attributes of the line drawings, but somewhat stronger stimulus control was exerted by the location of the added component than by its shape. Across all 8 pigeons, there was an inverse relation between stimulus control by component shape and component location. These results document pigeons' joint processing of "what" and "where" information in visual discrimination learning.