Some temporal factors affecting conditional discrimination

Abstract

Pigeons acquired a serial conditional discrimination in which the onset of one of two colors (the instructional cue) on the center key preceded the onset of a white light (the trial cue) on one of two side keys. An autoshaping preparation was employed, in which food was delivered depending upon the color-side combination. Five groups of birds were studied at instructional cue durations of either 30 or 60 sec, and trial cue durations of 3, 6, or 12 sec. These temporal parameters allowed for different ratios of the instructional stimulus duration (I) to the trial stimulus duration (T), while keeping the absolute duration of the instructional stimulus constant, and for different absolute durations of the instructional stimulus, while keeping the I/T ratio constant. These manipulations were studied with either a 30 or a 60-sec cycle (the interval between the onset of the intertriai interval and the offset of the trial cue), thus permitting examination of the cycle duration to trial duration ratios as well. The results showed that the larger the value of I relative to that of T, the greater the final level of accuracy; this implicates the I/T ratio as a controlling variable. In contrast, the larger the cycle duration (C) relative to T, the greater the rate of responding to the trial stimulus, which is consistent with previous findings in autoshaping studies. These results suggest that whereas the C/T ratio directly influences response rate, the I/T ratio affects accuracy in a serial conditional discrimination.