Jessica P. Stagner

Maladaptive choice behaviour by pigeons: an animal analogue and possible mechanism for gambling (sub-optimal human decision-making behaviour)

Consistent with human gambling behaviour but contrary to optimal foraging theory, pigeons showed maladaptive choice behaviour in experiment 1 by choosing an alternative that provided on average two food pellets over an alternative that provided a certain three food pellets. On 20 per cent of the trials, choice of the two-pellet alternative resulted in a stimulus that always predicted ten food pellets; on the remaining 80 per cent of the trials, the two-pellet alternative resulted in a different stimulus that always predicted zero food pellets. Choice of the three-pellet alternative always resulted in three food pellets. This choice behaviour mimics human monetary gambling in which the infrequent occurrence of a stimulus signalling the winning event (10 pellets) is overemphasized and the more frequent occurrence of a stimulus signalling the losing event (zero pellets) is underemphasized, compared with the certain outcome associated with not gambling (the signal for three pellets). In experiment 2, choice of the two-pellet alternative resulted in ten pellets with a probability of 20 per cent following presentation of either stimulus. Choice of the three-pellet alternative continued to result in three food pellets. In this case, the pigeons reliably chose the alternative that provided a certain three pellets over the alternative that provided an average of two pellets. Thus, in experiment 1, the pigeons were responding to obtain the discriminative stimuli signalling reinforcement and the absence of reinforcement, rather than to obtain the variability in reinforcement.

Suboptimal Choice Behavior by Pigeons

Contrary to the law of effect and optimal foraging theory, pigeons show suboptimal choice behavior by choosing an alternative that provides 20% reinforcement over another that provides 50% reinforcement. They choose the 20% reinforcement alternative—in which 20% of the time, that choice results in a stimulus that always predicts reinforcement, and 80% of the time, it results in another stimulus that predicts its absence—rather than the 50% reinforcement alternative, which results in one of two stimuli, each of which predicts reinforcement 50% of the time. This choice behavior may be related to suboptimal human monetary gambling behavior, because in both cases, the organism overemphasizes the infrequent occurrence of the winning event and underemphasizes the more frequent occurrence of the losing event.

Suboptimal Choice by Pigeons May Result from the Diminishing Effect of Nonreinforcement

Pigeons prefer an alternative that provides them with a stimulus 20% of the time that predicts 10 pellets of food and a different stimulus 80% of the time that predicts 0 pellets, over an alternative that provides them with a stimulus that always predicts 3 pellets of food, even though the preferred alternative provides them with considerably less food. It appears that the stimulus that predicts 10 pellets acts as a strong conditioned reinforcer, despite the fact that the stimulus that predicts 0 pellets occurs 4 times as often. In the present research, we tested the hypothesis that early in training conditioned inhibition develops to the 0-pellet stimulus, but later in training it dissipates. We trained pigeons with a hue as the 10-pellet stimulus and a vertical line as the 0-pellet stimulus. To assess the inhibitory value of the vertical line, we compared responding to the 10-pellet hue with responding to the compound of the 10-pellet hue and the vertical line early in training and once again late in training, using both a within-subject design (Experiment 1) and a between-groups design (Experiment 2). We found that there was a significant reduction in inhibition between the early test (when pigeons chose optimally) and late test (when choice was suboptimal). Thus, the increase in suboptimal choice may result from the decline in inhibition to the 0-pellet stimulus. Implications for human gambling behavior are considered.

Midsession reversal learning: why do pigeons anticipate and perseverate?

Past research has shown that when given a simultaneous visual-discrimination midsession reversal task, pigeons typically anticipate the reversal well before it occurs and perseverate after it occurs. It appears that they use the estimation of time (or trial number) into the session, rather than (or in addition to) the more reliable cue, the outcome from the previous trial (i.e., a win–stay/lose–shift response rule), to determine which stimulus they should choose. In the present research, we investigated several variables that we thought might encourage pigeons to use a more efficient response strategy. In Experiment 1, we used a treadle-stepping response, rather than key pecking, to test the hypothesis that reflexive key pecking may have biased pigeons to estimate the time (or trial number) into the session at which the reversal would occur. In Experiment 2, we attempted to make the point of reversal in the session more salient by inserting irrelevant trials with stimuli different from the original discriminative stimuli, and for a separate group, we added a 5-s time-out penalty following incorrect choices. The use of a treadle-stepping response did not improve reversal performance, and although we found some improvement in reversal performance when the reversal was signaled and when errors resulted in a time-out, we found little evidence for performance that approached the win–stay/lose–shift accuracy shown by rats.

Pigeons Prefer Conditional Stimuli Over Their Absence: A Comment on Roberts et al. (2009)

Recently, Roberts et al. (2009) have suggested that pigeons performing delayed matching-to-sample appear unwilling to request to see the sample again (or even for the first time) prior to choice, even if that choice would result in an increase in matching accuracy. In each of their four experiments, however, presentation (Experiments 3 & 4) or representation of the sample (Experiments 1 & 2) resulted in an added delay to reinforcement. Thus, the pigeons had to choose between an immediate reinforcer on about 50% of the trials and a delayed reinforcer on a significantly higher percentage of the trials. In the present research, when we equated the two alternatives for delay to reinforcement, we found that pigeons generally showed a significant preference for trials with a relevant sample over trials with an irrelevant sample. When the contingencies were reversed, most of the pigeons reversed their preference. Although these results do not present evidence for metacognition, they do show that pigeons are sensitive to the potential for a higher probability of reinforcement when delay to reinforcement is controlled.

Do pigeons prefer alternatives that include near-hit outcomes?

Pigeons show suboptimal choice on a gambling-like task similar to that shown by humans. Humans also show a preference for gambles in which there are near hits (losses that come close to winning). In the present research, we asked if pigeons would show a preference for alternatives with near-hit-like trials. In Experiment 1, we included an alternative that presented a near hit, in which a stimulus associated with reinforcement (a presumed conditioned reinforcer) changed to a stimulus associated with the absence of reinforcement (a presumed conditioned inhibitor). The pigeons tended to avoid this alternative. In Experiment 2, we varied the duration of the presumed conditioned reinforcer (2 vs. 8 s) that changed to a presumed conditioned inhibitor (8 vs. 2 s) and found that the longer the conditioned reinforcer was presented, the more the pigeons avoided it. In Experiment 3, the near-hit alternative involved an ambiguous stimulus for 8 s that changed to a presumed conditioned reinforcer (or a presumed conditioned inhibitor) for 2 s, but the pigeons still avoided it. In Experiment 4, we controlled for the duration of the conditioned reinforcer by presenting it first for 2 s followed by the ambiguous stimulus for 8 s. Once again, the pigeons avoided the alternative with the near-hit trials. In all 4 experiments, the pigeons tended to avoid alternatives that provided near-hit-like trials. We concluded that humans may be attracted to near-hit trials because near-hit trials give them the illusion of control, whereas this does not appear to be a factor for pigeons.

Do pigeons prefer information in the absence of differential reinforcement

Prior research has indicated that pigeons do not prefer an alternative that provides a sample (for matching to sample) over an alternative that does not provide a sample (i.e., there is no indication of which comparison stimulus is correct). However, Zentall and Stagner (Journal of Experimental Psychology. Animal Behavior Processes 36:506–509, 2010) showed that when delay of reinforcement was controlled, pigeons had a strong preference for matching over pseudomatching (i.e., there was a sample, but it did not indicate which comparison stimulus was correct). Experiment 1 of the present study replicated and extended the results of the Zentall and Stagner (Journal of Experimental Psychology. Animal Behavior Processes 36:506–509, 2010) study by including an identity relation between the sample and one of the comparison stimuli in both the matching and pseudomatching tasks. In Experiment 2, in which we asked whether the pigeons would still prefer matching if we equated the two tasks for probability of reinforcement, we found no systematic preference for matching over pseudomatching. Thus, it appears that in the absence of differential reinforcement, the information provided by a sample that signals which of the two comparison stimuli is correct is insufficient to produce a preference for that alternative.

The Monty Hall dilemma in pigeons: Effect of investment in initial choice

In the Monty Hall dilemma, humans are initially given a choice among three alternatives, one of which has a hidden prize. After choosing, but before it is revealed whether they have won the prize, they are shown that one of the remaining alternatives does not have the prize. They are then asked whether they want to stay with their original choice or switch to the remaining alternative. Although switching results in obtaining the prize two thirds of the time, humans consistently fail to adopt the optimal strategy of switching even after considerable training. Interestingly, there is evidence that pigeons show more optimal switching performance with this task than humans. Because humans often view even random choices already made as being more valuable than choices not made, we reasoned that if pigeons made a greater investment, it might produce an endowment or ownership effect resulting in more human-like suboptimal performance. On the other hand, the greater investment in the initial choice by the pigeons might facilitate switching behavior by helping them to better discriminate their staying versus switching behavior. In Experiment 1, we examined the effect of requiring pigeons to make a greater investment in their initial choice (20 pecks rather than the usual 1 peck). We found that the increased response requirement facilitated acquisition of the switching response. In Experiment 2, we showed that facilitation of switching due to the increased response requirement did not result from extinction of responding to the initially chosen location.

Guilt by association and honor by association: The role of acquired equivalence

Guilt by association and honor by association are two types of judgments that suggest that a negative or positive quality of a person or object can transfer to another person or object, merely by co-occurrence. Most examples have been demonstrated under conditions of direct associations. Here, we provide experimental evidence of guilt by association and honor by association via indirect associations. We show that participants may treat two individuals alike if they have been separately paired with a common event using an acquired-equivalence paradigm. Our findings suggest that association fallacies can be examined using a paradigm originally developed for research with nonhuman animals and based on a representation mediation account.