Preferences for wavelength and intensity in rhesus monkeys: fact or artifact?

10 adult male rhesus monkeys were tested to determine whether systematic preferences existed for specific color or brightness of visual stimuli. In contrast with previous reports no significant preferences for either specific hues or brightness levels were found. Perhaps methodological or subject variables may be responsible for preferential responding in other situations and account for the present inability to confirm prior work on preferences for color and brightness.

Suppression of visual observing by rhesus monkeys produced by conditioned aversive visual stimuli.

Nine rhesus monkeys were tested in a visual observing situation to determine the influence of conditioned aversive visual stimulation. A set of meaningless visual stimuli was selected on the basis of cumulative frequency and cumulative duration of observing during a pretest phase of the experiment. Three subsets of stimuli (low, medium, high) were formed indicating level of observing during pretesting. A portion of the "medium" category of slides then served as conditioned stimuli in a classical conditioning procedure by being paired with electric shock. Following conditioning the entire set of stimuli was again presented in a visual observing situation. The results showed a significant decrease in both frequency and duration of observing of the slides with conditioned aversive qualities, relative to non-shock control slides. These findings support an aversion-produced suppression of observing relatively unconfounded by methodological, procedural, and other differences existing among previous reports on the role of fear or anxiety in this context.