Recent Research
Pattison, K. F., Zentall, T. R., & Watanabe, S. (2012). Sunk cost: Pigeons (Columba livia) to show bias to complete a task rather than shift to another. Journal of Comparative Psychology, 126, 1-9. doi: 10.1037/a0023826.
The sunk cost effect involves the bias to stay with an alternative because one has already invested resources, even when there is a better alternative available. In a series of experiments, at various points during a 30-peck requirement, pigeons (Columba livia) could choose between completing the response requirement (at a different location in Experiment 1 or the same location in Experiments 3 and 4) and switching to a constant number of pecks. In three experiments, the pigeons showed a bias to complete the pecks already started, even when that required more pecking. We also demonstrated that the bias depended on the initial investment and was not produced merely because the pigeons preferred a variable alternative over a fixed alternative. The deviation from optimal choice suggests that pigeons show a bias similar to the sunk cost effect in humans.
Read Entire ArticleRayburn-Reeves, R. M., Stagner, J. P., Kirk, C. R. & Zentall, T. R. (2013). Reversal learning in rats (Rattus norvegicus) and pigeons (Columba livia): Qualitative differences in behavioral flexibility. Journal of Comparative Psychology, 127, 202-211. doi: 10.1037/a0026311.
Research has shown that pigeons given a simultaneous visually-based discrimination reversal, in which a single reversal occurs at the midpoint of each session, consistently show anticipation prior to the reversal as well as perseveration after the reversal, suggesting that they use a less effective cue (time or trial number into the session) than what would be optimal to maximize reinforcement (local feedback from the most recent trials). In the present research, pigeons and rats were tested with a simultaneous spatial discrimination midsession reversal. Pigeons showed remarkably similar errors in anticipation and perseveration as with visual stimuli, thereby continuing to show the suboptimal use of time as a cue, whereas rats showed no anticipatory errors and very few perseverative errors, suggesting that they used local feedback as a cue, thus more nearly optimizing reinforcement. To further test the rats’ flexibility, they were then tested with a variable point of reversal and then with multiple points of reversal within a session. Results showed that the rats effectively maximized reinforcement by developing an approximation to a win-stay/lose-shift rule. The greater efficiency shown by rats with this task suggests that they are better able to use the feedback from their preceding choice as the basis of their future choice. The difference in cue preference further suggests a qualitative difference in acquisition of the midsession reversal task between pigeons and rats.
Read Entire ArticleStagner, J. P., Case, J. P., Sticklen, M. F., Duncan, A. K., & Zentall, T. R. (2015). Do pigeons prefer alternatives that include near-hit outcomes? Journal of Experimental Psychology: Animal Behavior Processes, 41, 247-254. doi: 10.1037/xan0000069.
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.
Read Entire ArticleZentall, T. R., & Laude, J. R. (2013). Do pigeons gamble? I wouldn’t bet against it. Current Directions in Psychological Science, 22, 271-277. doi: 10.1177/0963721413480173.
Human gambling generally involves suboptimal choice because the expected return is usually less than the investment. We have found that animals, too, choose suboptimally under similar choice conditions. Pigeons, like human gamblers, show an impaired ability to objectively assess overall probabilities and amounts of reinforcement when a rare, high value outcome (analogous to a jackpot in human gambling) is presented in the context of more frequently occurring losses. More specifically, pigeons prefer a low-probability, high-reward outcome over a guaranteed low-reward outcome with a higher overall value. Furthermore, manipulations assumed to increase impulsivity (pigeons maintained at higher levels of motivation for food and pigeons housed in individual cages) result in increased suboptimal choice. They do so presumably because they function to increase attraction to the signal for the low-probability, high-reward outcomes rather than consider the more global probability of reinforcement associated with each alternative.
Read Entire ArticleZentall, T. R., Laude, J. R., Case, J. P. & Daniels, C. W. (2014). Less means more for pigeons but not always. Psychonomic Bulletin & Review, 21, 1623-1628. doi: 10.3758/s13423-014-0626-1.
When humans are asked to judge the value of a set of objects of excellent quality, they often give this set higher value than those same objects with the addition of some of lesser quality. This is an example of the affect heuristic, often referred to as the less-is-more effect. Monkeys and dogs, too, have shown this suboptimal effect. But in the present experiments, normally hungry pigeons chose optimally: a preferred food plus a less–preferred food over a more-preferred food alone. In Experiment 2, however, pigeons on a less-restricted diet showed the suboptimal less-is-more effect. Choice on control trials indicated that the effect did not result from the novelty of two food items versus one. The effect in the less food- restricted pigeons appears to result from the devaluation of the combination of the food items by the presence of the less-preferred food item. The reversal of the effect under greater food restriction may occur because, as motivation increases, the value of the less-preferred food increases faster than the value of the more-preferred food, thus decreasing the difference in value between the two foods.
Read Entire ArticleZentall, T. R. (2012). Perspectives on social learning. Journal of Comparative Psychology, 126, 114-128. doi: 10.1037/a0025381.
Observational learning is presumed to have occurred when an organism copies an improbable action or action outcome that it has observed and the matching behavior cannot be explained by an alternative mechanism. Psychologists have been particularly interested in the form of observational learning known as imitation and in how to distinguish imitation from other processes. To successfully make this distinction, one must disentangle the degree to which behavioral similarity results from (a) predisposed behavior, (b) increased motivation resulting from the presence of another animal, (c) attention drawn to a place or object, (d) learning about the way the environment works, as distinguished from what we think of as (e) imitation (the copying of the demonstrated behavior). Several of the processes that may be involved in observational learning are reviewed, including social facilitation, stimulus enhancement, several kinds of emulation, and various forms of imitation.
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