Pigeons rank-order responses to temporally sequential stimuli

Abstract

We explored pigeons' ability to learn a particular sequence of stimuli in which the durations of each stimulus varied among trials, where the first response at the end of the sequence was reinforced. In Experiment 1A, we found that pigeons failed to use the whole sequence of three stimuli to predict food reinforcement, and instead responded only to the third, "rewarded" stimulus. When rewarded (1-2-3) and nonrewarded (2-1-3) sequences were used in a go/no-go procedure in Experiment 1B, however, pigeons showed a tendency to rank-order responding, with higher response rates to the second than to the first stimulus, as well as lower response rates to the third stimulus on nonrewardedsequence trials. In Experiment 2, pigeons showed rudimentary rank-ordering of five stimuli in sequence, with lower responding to the final stimulus on nonrewarded trials, even when the sequence presented differed from the rewarded sequence only in a reversal of the second and third stimuli. Pigeons were capable of using ordinal information in a temporal task, but only when that information was easily discriminable and led to explicit consequences (i.e., rewarded vs. nonrewarded sequences).Keywords Pigeons . Timing . Ordinal . Interval . Serial learning/memory In a typical environment over the course of a day, animals are required to produce multiple complex behaviors in response to a complicated array of spatiotemporally graded stimuli. Because animals cannot produce all behaviors at all times, and because stimuli are not available at all times, efficient performance requires organizing behavior in some manner in order to maximize reward. Although the laws of conditioning may explain responses made to single stimuli by animals in lab experiments, those explanations often do not extend to the ability to organize behaviors when more complex organizations of stimuli are encountered in a natural environment. For example, if an array of foraging patches replenish on temporally distinct schedules, how does an animal organize its foraging behavior to maximize its reward while minimizing effort and predation risk? Sequence discriminationAnimals have previously been shown in a wide variety of tasks to be able both to discriminate and to produce sequences of stimuli in particular orders. Shimp (1976) presented pigeons with a sequence of three white Xs on left-and right-side keys in a random order. After the sequence was presented, the pigeon was presented with one of three hues on the center key to peck, and once it had done so, it was presented with that same hue on both side keys. The subjects were reinforced for pecking the side key on which one white X had been presented in the sequence, according to the positional cue provided by the hue: first in sequence for red, second for blue, and third for white. For example, the initial sequence left-right-left would correspond to pecking left on a red test cue, right on a blue test cue, or left on a white test cue. Although pigeons' accuracy in this task was modulated by the retention interv...

It's All a Matter of Time: Interval Timing and Competition for Stimulus Control

“…Subsequent time-place experiments ruled out that rats used ordinal measurement to track food locations, and instead use either or both of interval and circadian timing to predict the locations of food (Crystal, 2009;Pizzo & Crystal, 2002. We also demonstrated that pigeons have difficulty learning a sequence of stimuli presented across a variable interval with one terminal reinforcer (McMillan & Roberts, 2013b). With extensive training, pigeons were able to demonstrate weakly rank-ordered responding to up to five stimuli in sequence, but only with explicit training wherein one sequence terminated in food and others did not.…”