Instructional and trial durations in conditional discrimination

Pigeons acquired a conditional discrimination in an autoshaping procedure in which a color (instructional) stimulus signalled which positional (trial) stimulus would be followed by food. The design employed temporal parameters which allowed different ratios of the instructional stimulus (I) duration to the trial stimulus (T) duration keeping the absolute duration of the instructional stimulus constant, and different absolute durations of the instructional stimulus keeping the ratio of the instructional to trial stimulus durations constant. These manipulations were studied at two cycle durations, permitting the examination of the cycle to trial ratios as well. Six groups of birds were studied at instructional stimulus durations of either 60-, 30-, or 6-sec and trial durations of either 12-, 6-, or 3- sec. Groups were exposed to either a 60- or 30-sec cycle duration. The results showed that the larger the duration of the instructional stimulus relative to the trial stimulus, the greater the rate and final level of acquisition, implicating the ratio of I/T as a controlling variable. There was one exception to this general finding, a group exposed to the simultaneous presentation of the instructional and trial stimuli. A simple model of instructional control based on temporal factors was presented