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Zentall, T. R., & Kaiser, D. H. (2005). Interval timing with gaps: gap ambiguity as an alternative to temporal decay. J Exp Psychol Anim Behav Process, 31(4), 484–486.
Abstract: C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration and salience of the gap. Thus, animals should pause with short, nonsalient gaps but should reset their clock with longer, salient gaps. The present authors suggest that the ambiguity of the gap (i.e., the similarity between the gap and the intertrial interval in both appearance and relative duration) causes the animal to actively reset the clock and prevents adequate assessments of the fate of timed intervals prior to the gap. Furthermore, when the intertrial interval is discriminable from the gap, the evidence suggests that timed intervals prior to the gap are not lost but are retained in memory.
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Martin, T. I., & Zentall, T. R. (2005). Post-choice information processing by pigeons. Anim. Cogn., 8(4), 273–278.
Abstract: In a conditional discrimination (matching-to-sample), a sample is followed by two comparison stimuli, one of which is correct, depending on the sample. Evidence from previous research suggests that if the stimulus display is maintained following an incorrect response (the so-called penalty-time procedure), acquisition by pigeons is facilitated. The present research tested the hypothesis that the penalty-time procedure allows the pigeons to review and learn from the maintained stimulus display following an incorrect choice. It did so by including a penalty-time group for which, following an incorrect choice, the sample changed to match the incorrect comparison, thus providing the pigeons with post-choice 'misinformation.' This misinformation group acquired the matching task significantly slower than the standard penalty-time group (that had no change in the sample following an error). Furthermore, acquisition of matching by a control group that received no penalty time fell midway between the other two groups, suggesting that the pigeons did not merely take more care in making choices because of the aversiveness of penalty-time. Thus, it appears that in the acquisition of matching-to-sample, when the stimulus display is maintained following an incorrect choice, the pigeons can review or acquire information from the display. This is the first time that such an effect has been reported for a nonhuman species.
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Clement, T. S., & Zentall, T. R. (2003). Choice based on exclusion in pigeons. Psychon Bull Rev, 10(4), 959–964.
Abstract: When humans acquire a conditional discrimination and are given a novel-sample-comparison choice, they often reject a comparison known to be associated with a different sample and choose the alternative comparison by default (or by exclusion). In Experiment 1, we found that if, following matching training, we replaced both of the samples, acquisition took five times longer than if we replaced only one of the samples. Apparently, the opportunity to reject one of the comparisons facilitated the association of the other sample with the remaining comparison. In Experiment 2, we first trained pigeons to treat two samples differently (to associate Sample A with Comparison 1 and Sample B with Comparison 2) and then trained them to associate one of those samples with a new comparison (e.g., Sample A with Comparison 3) and to associate a novel sample (Sample C) with a different, new comparison (Comparison 4). When Sample B then replaced Sample C, the pigeons showed a significant tendency to choose Comparison 4 over Comparison 3. Thus, when given the opportunity, pigeons will choose by exclusion.
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Klein, E. D., & Zentall, T. R. (2003). Imitation and affordance learning by pigeons (Columba livia). J Comp Psychol, 117(4), 414–419.
Abstract: The bidirectional control procedure was used to determine whether pigeons (Columba livia) would imitate a demonstrator that pushed a sliding screen for food. One group of observers saw a trained demonstrator push a sliding screen door with its beak (imitation group), whereas 2 other groups watched the screen move independently (possibly learning how the environment works) with a conspecific either present (affordance learning with social facilitation) or absent (affordance learning alone). A 4th group could not see the screen being pushed (sound and odor control). Imitation was evidenced by the finding that pigeons that saw a demonstrator push the screen made a higher proportion of matching screen pushes than observers in 2 appropriate control conditions. Further, observers that watched a screen move without a demonstrator present made a significantly higher proportion of matching screen pushes than would be expected by chance. Thus, these pigeons were capable of affordance learning.
Keywords: Animals; *Behavior, Animal; Columbidae; Cues; *Imitative Behavior; *Learning; Odors; Sound
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Kaiser, D. H., Zentall, T. R., & Neiman, E. (2002). Timing in pigeons: effects of the similarity between intertrial interval and gap in a timing signal. J Exp Psychol Anim Behav Process, 28(4), 416–422.
Abstract: Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors found that when ambient conditions during the gap were similar to the ITI, pigeons tended to reset memory, but when ambient conditions during the gap were different from the ITI, pigeons tended to stop timing, retain the duration of the stimulus in memory, and add to that time when the stimulus reappeared. Thus, when the gap was unambiguous, pigeons timed accurately.
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Zentall, T. R., Clement, T. S., Bhatt, R. S., & Allen, J. (2001). Episodic-like memory in pigeons. Psychon Bull Rev, 8(4), 685–690.
Abstract: It has been proposed that memory for personal experiences (episodic memory, rather than semantic memory) relies on the conscious review of past experience and thus is unique to humans. In an attempt to demonstrate episodic-like memory in animals, we first trained pigeons to respond to the (nonverbal) question “Did you just peck or did you just refrain from pecking?” by training them on a symbolic matching task with differential responding required to the two line-orientation samples and reinforcing the choice of a red comparison if they had pecked and the choice of a green comparison if they had not pecked. Then, in Experiment 1, after providing the conditions for (but not requiring) the pigeons to peck at one new stimulus (a yellow hue) but not at another (a blue hue), we tested them with the new hue stimuli and the red and green comparisons. In Experiment 2, we tested the pigeons with novel stimuli (a circle, which they spontaneously pecked, and a dark response key, which they did not peck) and the red and green comparisons. In both experiments, pigeons chose the comparison appropriate to the response made to the test stimulus. Thus, the pigeons demonstrated that they could remember specific details about their past experiences, a result consistent with the notion that they have the capacity for forming episodic-like memories.
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Clement, T. S., Weaver, J. E., Sherburne, L. M., & Zentall, T. R. (1998). Simultaneous discrimination learning in pigeons: value of S- affects the relative value of its associated S+. Q J Exp Psychol B, 51(4), 363–378.
Abstract: In a simple simultaneous discrimination involving a positive stimulus (S+) and a negative stimulus (S-), it has been hypothesized that positive value can transfer from the S+ to the S- (thus increasing the relative value of the S-) and also that negative value can transfer from the S- to the S+ (thus diminishing the relative value of the S+; Fersen, Wynne, Delius, & Staddon, 1991). Evidence for positive value transfer has been reported in pigeons (e.g. Zentall & Sherburne, 1994). The purpose of the present experiments was to determine, in a simultaneous discrimination, whether the S- diminishes the value of the S+ or the S- is contrasted with the S+ (thus enhancing the value of the S+). In two experiments, we found evidence for contrast, rather than value transfer, attributable to simultaneous discrimination training. Thus, not only does the S+ appear to enhance the value of the S-, but the S- appears to enhance rather than reduce the value of the S+.
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Zentall, T. R., & Sherburne, L. M. (1994). Role of differential sample responding in the differential outcomes effect involving delayed matching by pigeons. J Exp Psychol Anim Behav Process, 20(4), 390–401.
Abstract: The role of differential sample responding in the differential outcomes effect was examined. In Experiment 1, we trained pigeons on a one-to-many matching task with differential sample responding required. Differential outcomes were associated with samples and comparisons, with comparisons only, or with neither samples nor comparisons. Slopes of delay functions for trials with pecked versus nonpecked samples suggested use of a single-code-default strategy in the nondifferential-outcomes group but not in the differential-outcomes groups. In Experiment 2, differential sample responding and differential outcomes were manipulated independently. Again, there were significant differences in the relative slopes of the delay functions. Results suggest that differential outcomes exert their effect independently of differential sample responding.
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Nallan, G. B., Pace, G. M., McCoy, D. F., & Zentall, T. R. (1979). Temporal parameters of the feature positive effect. Am J Psychol, 92(4), 703–710.
Abstract: Trial duration and intertrial interval duration were parametrically varied between groups of pigeons exposed to a discrimination involving the presence vs. the absence of a dot. Half the groups received the dot as the positive stimulus (feature positive groups) and half the groups received the dot as the negative stimulus (feature negative groups). Faster learning by the feature positive birds (feature positive effect) was found when the trial duration was short (5 sec) regardless of whether the intertrial interval was short (5 sec) or long (30 sec). No evidence for a feature positive effect was found when the trial duration was long (30 sec) regardless of the length of the intertrial interval (30 sec or 180 sec). The results suggest that short trial duration is a necessary condition for the occurrence of the feature positive effect, and neither intertrial interval nor trial duration/intertrial interval ratio are important for its occurrence. The suggestion that mechanisms underlying the feature positive effect and autoshaping might be similar was not supported by the present experiment since the trial duration/intertrial interval ration parameter appears to play an important role in autoshaping but not the feature positive effect.
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DiGian, K. A., Friedrich, A. M., & Zentall, T. R. (2004). Discriminative stimuli that follow a delay have added value for pigeons. Psychon Bull Rev, 11(5), 889–895.
Abstract: Clement, Feltus, Kaiser, and Zentall (2000) reported that pigeons prefer discriminative stimuli that require greater effort (more pecks) to obtain over those that require less effort. In the present experiment, we examined two variables associated with this phenomenon. First, we asked whether delay of reinforcement, presumably a relatively aversive event similar to effort, would produce similar effects. Second, we asked whether the stimulus preference produced by a prior relatively aversive event depends on its anticipation. Anticipation of delay was accomplished by signaling its occurrence. Results indicated that delays can produce preferences similar to those produced by increased effort, but only if the delays are signaled.
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