Spatial memory for food hidden by rats (Rattus norvegicus) on the radial maze: Studies of memory for where, what, and when

Rats (Rattus norvegicus) were allowed to hide food items on an 8-arm radial maze by carrying the items from the center to boxes at the end of each arm. Retrieval tests given after rats had hidden 4 items showed that they selectively returned to the maze arms where food had been hidden (Experiments 1 and […]

Spontaneous discrimination of natural stimuli by chimpanzees (Pan troglodytes)

Six chimpanzees ( Pan troglodytes) were presented with pairs of color photographic images of 5 different categories of animals (cat, chimp, gorilla, tiger, fish). The subjects responded to each pair using symbols for “same” and “different.” Both within- and between-category discriminations were tested, and all chimpanzees classified the image pairs in accordance with the 5 […]

Use of Position and Feature Cues in Discrimination Learning by the Whiptail Lizard (Cnemidophorus inornatus)

Animals use a variety of cue types to locate and discriminate objects. The ease with which particular cue types are learned varies across species and context. An enormous literature contains comparisons of spatial cue use to use of other cue types, but few experiments examine the ease with which various nonspatial cues are learned. In […]

Ordinality and inferential abilities of a grey parrot (Psittacus erithacus)

A grey parrot (Psittacus erithacus), able to label the color of the bigger or smaller object in a pair (I. M. Pepperberg & M. V. Brezinsky, 1991), to vocally quantify < or =6 item sets (including heterogeneous subsets; I. M. Pepperberg, 1994), and separately trained to identify Arabic numerals 1-6 with the same vocal English […]

Spontaneous Use of Magnitude Discrimination andOrdination by the Orangutan (Pongo pygmaeus)

The ability to discriminate quantity is descriptive of general cognitive ability. In this study, the authors presented 2 orangutans (Pongo pygmaeus) with a quantity judgment task. Each trial consisted of 2 choices, ranging from 1 to 6 food items in each. The orangutan chose 1 of the quantities, which was removed, and the remaining array […]

Stimulus discrimination by horses under scotopic conditions

Scotopic vision in horses (Equus caballus) was investigated using behavioral measurements for the first time. Four horses were tested for the ability to make simple visual discriminations of geometric figures (circles and triangles) under various brightness levels within an enclosed building. Measurements of brightness ranging from 10.37 to 24.12 magnitudes per square arcsecond (mag/arcsec2; in […]