Thomas R Zentall

Thomas R Zentall
University of Kentucky | UKY · Department of Psychology

About

403
Publications
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11,114
Citations
Citations since 2016
76 Research Items
3986 Citations
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600
20162017201820192020202120220100200300400500600

Publications

Publications (403)
Article
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When pigeons learn a conditional discrimination in which a sample stimulus indicates which of two comparison stimuli is correct Skinner (1950) proposed that they learn a chain involving the sample, the correct comparison stimulus, and the reinforcer. This implies that they do not learn to reject the incorrect comparison stimulus and the sameness re...
Article
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When pigeons learn matching-to-sample or nonmatching-to-sample there is good evidence that they can transfer that learning to novel stimuli. But early evidence suggests that in the rate of task acquisition, there is no benefit from a matching relation between the sample and the correct or incorrect comparison stimulus. In the present research we tr...
Article
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Pigeons typically prefer a 20% probability of signaled reinforcement over a 50% probability of unsignaled reinforcement. There is even evidence that they prefer 50% signaled reinforcement over 100% reinforcement. It has been suggested that this effect results from contrast between the expected probability of reinforcement (e.g., 50%) at the time of...
Article
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When humans face probabilistic outcomes, their choices often depend on whether the choice is framed in terms of losses or gains. In the present research, we gave pigeons a choice between risky (variable) outcomes and safe (constant) outcomes that resulted in the same net reward. In Experiment 1, in which the outcomes represented a loss, the pigeons...
Article
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In human learning a distinction has been made between implicit and explicit learning. Implicit learning is thought involve automatic processes of the kind involved in Pavlovian conditioning, while explicit learning is thought to involve conscious hypothesis testing and rule formation, in which the ability to report the rule used to learn the task i...
Article
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Procrastination involves an irrational putting off of engaging in a course of action, in spite of expecting to be worse off for the delay. I suggest that to understand the processes underlying procrastination one should examine its relation to several behavioral procedures that have been studied in humans and other animals. For example, in delay di...
Article
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In a simultaneous discrimination, pigeons are presumed to learn to about the correct stimulus, but they may also learn to avoid the incorrect stimulus. Similarly, in a conditional discrimination, they are presumed to learn about the relation between the sample stimulus and the correct comparison stimulus but not about the incorrect comparison stimu...
Article
In the visual alternation task, pigeons learn to alternate between two stimuli (e.g., red and green) that vary randomly in location from trial to trial. The task is inherently difficult because animals tend to return to a stimulus to which they have just received reinforcement for responding. Williams (1971, Journal of the Experimental Analysis of...
Article
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Reference dependence refers to the reduced value of a reward that is less than expected, or the added value of a reward that is greater than expected. There is evidence that when pigeons are offered an alternative that has 1 pellet versus an alternative that has 2 pellets, but one of the two pellets offered will be removed, the pigeons prefer the o...
Article
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The humane treatment of animals suggests that they should be housed in an environment that is rich in stimulation and allows for varied activities. However, even if one’s main concern is an accurate assessment of their learning and cognitive abilities, housing them in an enriched environment can have an important effect on the assessment of those a...
Article
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Science is often perceived to be a self-correcting enterprise. In principle, the assessment of scientific claims is supposed to proceed in a cumulative fashion, with the reigning theories of the day progressively approximating truth more accurately over time. In practice, however, cumulative self-correction tends to proceed less efficiently than on...
Article
In humans, a distinction can be made between implicit or procedural learning (involving stimulus-response associations) and explicit or declarative learning (involving verbalizable rules) that is relatively easy to make in verbal humans. According to several investigators, it is also possible to make such a distinction in nonverbal animals. One way...
Article
The reverse-contingency task is a task in which one is given a choice between two rewards, but one receives the larger amount only if one chooses the smaller amount. This task is very difficult for chimpanzees unless the choice is between symbolic representations of the amounts. We found that pigeons can learn this task easily, if the reward amount...
Article
concept learning in pigeons is typically assessed by training subjects with one set of stimuli and demonstrating that they can transfer that learning to new stimuli. Converging evidence suggests that under a variety of conditions, pigeons do show evidence of conceptual same/difference learning that goes beyond the if-then chains proposed by Skinner...
Article
Optimal foraging theory suggests that animals have evolved to maximize their net rate of energy intake; all things being equal, they should leave a current depleting patch when an alternative patch would provide either more or sooner food. In nature, however, typically all things are not equal. For example, uncertainty about the value of alternativ...
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The hypothesis proposed by Macphail (1987) is that differences in intelligent behavior thought to distinguish different species were likely attributed to differences in the context of the tasks being used. Once one corrects for differences in sensory input, motor output, and incentive, it is likely that all vertebrate animals have comparable intell...
Article
In the midsession reversal task, pigeons are trained on a simultaneous two-alternative discrimination in which S1 is correct for the first half of the session and S2 is correct for the second half of the session. Optimally, pigeons should choose S1 until it stops being correct and choose S2 afterward. Instead, pigeons anticipate S2 too early and co...
Article
When humans make biased or suboptimal choices, they are often attributed to complex cognitive processes that are viewed as being uniquely human. Alternatively, several phenomena, such as suboptimal gambling behavior and cognitive dissonance (justification of effort) may be explained more simply as examples of the contrast between what is expected a...
Article
The ephemeral reward task consists of giving an animal a choice between two distinctive stimuli, A and B (e.g., black and white), on each of which is placed a bit of food. If the animal chooses the food on A, it gets that reinforcer, but the other stimulus, B, is removed, and the trial is over. If it chooses the food on B, however, it gets that foo...
Article
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Delaying reinforcement typically has been thought to retard the rate of acquisition of an association, but there is evidence that it may facilitate acquisition of some difficult simultaneous discriminations. After describing several cases in which delaying reinforcement can facilitate acquisition, we suggest that under conditions in which the magni...
Article
The traditional view of human procrastination is that engaging in an aversive task will be avoided until the anxiety associated with the consequences of missing the deadline exceeds the aversiveness of the task. Delay reduction theory suggests that there may be an additional mechanism, conditioned reinforcement associated with completion of the tas...
Article
In a midsession reversal task, the session begins with a simple simultaneous discrimination in which one stimulus (S1) is correct and the other stimulus (S2) is incorrect (S1+/S2-). At the midpoint of the session, the discrimination reverses and S2 becomes the correct choice (S2+/S1-). When choosing optimally, a pigeon should choose S1 until the fi...
Article
In the midsession reversal task, choice of one stimulus (S1) is correct for the first half of each session and choice of the other stimulus (S2) is correct for the last half of each session. Although humans and rats develop very close to what has been called a win-stay/lose-shift response strategy, pigeons do not. Pigeons start choosing S2 before t...
Article
The midsession reversal task involves a simple simultaneous discrimination in which, each session, choice of 1 stimulus (S1) is correct for the first 40 trials of each session, and choice of the other stimulus (S2) is correct for the remaining 40 trials. After considerable training with this task, pigeons typically continue to choose S2 too early (...
Article
Delay of reinforcement is generally thought to be inversely correlated with speed of acquisition. However, in the case of simultaneous discrimination learning, in which choice results in immediate reinforcement, delay of reinforcement can improve acquisition. For example, in the ephemeral reward task, animals are given a choice between two alternat...
Article
When humans procrastinate, they delay completing a required relatively aversive task. In the present experiments with pigeons, we considered the possibility that completing the task close to the deadline results in the formation of a stronger conditioned reinforcer. In Experiment 1, pigeons were given a choice between two chains: (a) a signaled lon...
Article
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In the five-term, transitive inference task used with animals, pigeons are trained on four simultaneous discrimination premise pairs: A + B −, B + C −, C + D −, D + E −. Typically, when tested with the BD pair, most pigeons show a transitive inference effect, choosing B over D. Two non-inferential hypotheses have been proposed to account for this e...
Article
The midsession reversal task involves a simultaneous discrimination in which choice of one stimulus (S1) is correct for the first 40 trials and choice of the other stimulus (S2) is correct for the last 40 trials of each 80-trial session. When pigeons are trained on the midsession reversal task, they appear to use the passage of time from the start...
Article
Full-text available
The midsession reversal task involves a simultaneous discrimination between Stimulus 1 (S1) and Stimulus 2 (S2) in which, for the first half of each session, choice of S1 is reinforced and S2 is not, and for the last half of each session, choice of S2 is reinforced and S1 is not. With this task, even after considerable training, pigeons tend to mak...
Article
This experiment tests the effects of a reducing the value of one stimulus compared to another. We hypothesize that in a midsession reversal task, accuracy would improve by devaluing choice of S2 relative to S1. A midsession reversal task requires a simultaneous discrimination between 2 stimuli (S1, S2), during which, halfway through the session the...
Article
Putting things off as long as possible (procrastination) is a well-known tendency. Less well known is the tendency to attempt to get things done as soon as possible, even if that involves extra effort (precrastination). Since its discovery in 2014, precrastination has been demonstrated in humans and animals and has recently been revealed in an anal...
Article
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When pigeons are given a choice between 50% signaled reinforcement and 100% reinforcement they typically do not choose optimally, sometimes even preferring 50% reinforcement. Smith and Zentall (J Exp Psychol Anim Behav Process 42:212–220, 2016) proposed that choice depends primarily on the predictive value of the signal for reinforcement associated...
Article
When animals make decisions that are suboptimal, it helps us to identify the processes that have evolved to produce this behavior. In an earlier article, I discussed three examples of suboptimal choice or bias (Zentall, 2016): (a) sunk cost, the tendency to continue on a losing project because of the amount already invested; (b) unskilled gambling,...
Article
The commentaries appropriately mention boundary conditions for the less is more effect (Beran, this issue; Carvalho et al., this issue) and the caution that choice behavior that seems suboptimal in the laboratory may be optimal in nature (Vasconcelos et al., this issue). Pisklak et al. (this issue) object to my definition of contrast to describe th...
Article
Timberlake (1993) proposed that much learning research can be better understood in the context of behavior systems theory. Learning theories generally have not considered how procedures may interact with evolutionarily prepared foraging contexts, thereby leading to anomalous conclusions. An example of such a conclusion is the apparent species diffe...
Article
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Animals are expected to minimize time and effort to reinforcement. Thus, not pecking should be preferred over pecking. However, even if time is held constant, pigeons often peck when it is allowed but not required (e.g., fixed time schedules), but with such schedules pecking may be adventitiously reinforced. In the present experiment, to better com...
Article
Object permanence, often viewed as a measure of human cognitive development, has also been used to assess animals’ cognitive abilities. Tests of object permanence have distinguished between visible displacement, in which an object may be placed into one of two (or more) containers to be retrieved, and invisible displacement, in which after the obje...
Article
Panoz-Brown et al. (Current Biology, 28, 1628–1634, 2018) present evidence to support the hypothesis that rats can replay their episode memory to determine which of a series of odors was at a particular location in the sequence. They also show that the hippocampus is likely involved in allowing the rats to replay those memories.
Article
Prior research has found that pigeons are indifferent between an option that always provides a signal for reinforcement and an alternative that provides a signal for reinforcement only 50% of the time (and a signal for the absence of reinforcement 50% of the time). This suboptimal choice suggests that the frequency of the signal for reinforcement p...
Article
Most models of choice assume a “tug of war” (ToW) between options present at the time of the choice, arguing that preferences are built on this process, and implying that adding options increases delay to act. In contrast, the sequential choice model (SCM) proposes that choices are driven by parallel expression of the mechanisms that control action...
Article
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It has been assumed that when pigeons learn how to match to sample, they learn simple stimulus-response chains but not the concept of sameness. However, transfer to novel stimuli has been influenced by pigeons’ tendency to be neophobic. We trained pigeons on matching (n = 7) and mismatching (n = 8) with colors as samples and, with each sample, one...
Article
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Rationale: Laboratory experiments often model risk through a choice between a large, uncertain (LU) reward against a small, certain (SC) reward as an index of an individual’s risk tolerance. An important factor generally lacking from these procedures are reward-associated cues that may modulate risk preferences. Objective: We tested whether the add...
Article
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The ephemeral-reward task involves providing subjects a choice between two distinctive stimuli, A and B, each containing an identical reward. If A is chosen, the food associated with A is obtained and the trial is over. If B is chosen, the food associated with B is obtained, but the food associated with A can be obtained as well. Thus, the food-max...
Article
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The failure of certain species to learn a particular task while others learn it easily can help identify the learning mechanisms involved. In the ephemeral reward task, animals are given a choice between two distinctive stimuli, A and B, each containing an identical bit of food. If they choose A they get the food on A and the trial is over. If they...
Article
Most research of comparative cognition has focused on the degree to which cognitive phenomena that have been reported in humans, especially children, can also be demonstrated in other animals. The value of such comparative research has not only been the finding that other animals show behavior that is qualitatively similar to that of humans but bec...
Article
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Procrastination is the tendency to put off initiation or completion of a task. Although people are typically known to procrastinate, recent research suggests that they sometimes “pre-crastinate” by initiating a task sooner than they need to (Rosenbaum et al. in Psychological Science, 25(7), 1487–1496, 2014). A similar finding of precrastination was...
Article
Animals choose suboptimally when provided with cues that signal whether reinforcement is coming or not. For example, pigeons do not prefer an alternative that always provides them with a signal for reinforcement over an alternative that provides them with a signal for reinforcement only half of the time and a signal for the absence of reinforcement...
Article
For over 100 years, Morgan's Canon has served as the criterion for distinguishing what appears to be complex cognitive processes shown by animals from simpler associative learning processes (Pavlovian and instrumental conditioning). Morgan's (1894) canon states “In no case is an animal activity to be interpreted in terms of higher psychological pro...
Article
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Individuals often face choices that have uncertain outcomes and have important consequences. As a model of this environment, laboratory experiments often offer a choice between an uncertain, large reward that varies in its probability of delivery against a certain but smaller reward as a measure of an individual’s risk aversion. An important factor...
Article
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The ephemeral reward task provides a subject with a choice between two alternatives A and B. If it chooses alternative A, reinforcement follows and the trial is over. If it chooses alternative B, reinforcement follows but the subject can also respond to alternative A which is followed by a second reinforcement. Thus, it would be optimal to choose a...
Article
Stimuli that are more predictive of subsequent reward also function as better conditioned reinforcers. Moreover, stimuli attributed with incentive salience function as more robust conditioned reinforcers. Some theories have suggested that conditioned reinforcement plays an important role in promoting suboptimal choice behavior, like gambling. The p...
Article
Slot machines are among the most popular forms of commercial gambling, and the high frequency of losses that come close to winning – near hits – in this game appears to contribute to its popularity. In the present experiment we tested if pigeons, similarly to humans, prefer an alternative that provides near-hit outcomes in a slot-machine-like task....
Article
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Human gambling generally involves taking a risk on a low probability high outcome alternative over the more economically optimal high probability low outcome alternative (not gambling). Surprisingly, although optimal foraging theory suggests that animals should be sensitive to the overall probability of reinforcement, the results of many experiment...
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There is evidence that impulsive decision-making is associated with errors in timing. However, there has been little attempt to identify the putative mechanism responsible for impulsive animals’ timing errors. One means of manipulating impulsivity in non-human animals is providing different levels of access to conspecifics. These preclinical models...
Article
Full-text available
The midsession reversal task involves a simultaneous discrimination between 2 stimuli (S1 and S2) in which, for the first half of each session, choice of S1 is reinforced and, for the last half, choice of S2 is reinforced. On this task, pigeons appear to time the occurrence of the reversal rather than using feedback from previous trials, resulting...
Article
Full-text available
Prior commitment has been found to facilitate choice of a larger later reward (e.g., healthy living) and avoid the impulsive choice of the smaller immediate reward (e.g., smoking, drug taking). In this research with pigeons, we investigated the ephemeral choice task in which pigeons are given a choice between two alternatives, A and B, with similar...
Article
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The cognitive ability of dogs can be assessed using tasks from the human developmental literature. A task that appears to have ecological relevance is the object-permanence task, in which performance hinges on understanding that an object continues to exist once it can no longer be seen. Although dogs are good at visible displacement tasks, in whic...
Article
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Pigeons have shown suboptimal gambling-like behavior when preferring a stimulus that infrequently signals reliable reinforcement over alternatives that provide greater reinforcement overall. As a mechanism for this behavior, recent research proposed that the stimulus value of alternatives with more reliable signals for reinforcement will be preferr...
Data
Experimental Data. This file contains all data used in the statistical and mathematical models of the present experiments. (XLSX)
Article
Full-text available
Recent research has examined a task in which choice of 1 alternative A provides reinforcement and in addition, allows access to alternative B that also provides reinforcement. However, although initial choice of B also provides reinforcement, it does not also allow access to A. Thus, optimal performance would be to always choose A. Curiously, Salwi...
Article
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Pigeons have sometimes shown a preference for a signaled 50% reinforcement alternative (leading half of the time to a stimulus that signaled 100% reinforcement and otherwise to a stimulus that signaled 0% reinforcement) over a 100% reinforcement alternative. We hypothesized that pigeons may actually be indifferent between the 2 alternatives with pr...
Article
It is well known that when humans are given a choice between two options, their preference is affected by the presence of a third. Generally, there is an increase in preference for the option closer to the third. We show that a shift in preference in the direction away from the third option can occur in animals. We gave pigeons a choice between A,...
Article
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The field of comparative cognition has been largely concerned with the degree to which animals have analogs of the cognitive capacities of humans (e.g., imitation, categorization), but recently attention has been directed to behavior that is judged to be biased or suboptimal. We and some of our colleagues have studied several of these and have foun...
Chapter
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It is well recognized that animals can acquire a new response by observing the behavior of others, however there remains some controversy concerning the mechanisms responsible for this learning. Of particular interest is observational learning, which is presumed to have occurred when an organism copies an improbable action or action-outcome that it...
Article
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When humans engage in commercial (totally probabilistic) gambling they are making suboptimal choices because the return is generally less than the investment. This review (a) examines the literature on pigeon suboptimal choice, (b) describes the conditions under which it occurs, (c) identifies the mechanisms that appear to be responsible for the ef...
Article
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We humans value intelligence because we tend to have more of it than other species. But the flexibility implied by intelligence is not as reliable as genetically predisposed behavior and is only valuable when environments change. Nevertheless, environments do change and many species do have the flexibility to adapt behaviorally to those changes eit...
Article
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The finding of reciprocal altruism in rats does not explain how such behavior came to be. Attributing it to a genetic predisposition or basic learning processes may not be what the authors had in mind, but the alternative, cultural learning, seems even less plausible for rats and perhaps is not even the primary basis for reciprocal altruism in huma...
Article
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Pigeons given a simultaneous spatial 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 maximiz...
Article
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The midsession reversal task involves a simple simultaneous discrimination that predictably reverses midway through a session. Under various conditions, pigeons generally both anticipate the reversal and perseverate once it has occurred, whereas rats tend to make very few of either kind of error. In the present research, we investigated the hypothe...
Article
Full-text available
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 alternati...
Article
Full-text available
In an analog of human gambling, pigeons prefer a suboptimal alternative that infrequently provides a signal that is reliably associated with reinforcement over the more optimal alternative that yields more reinforcement. We hypothesized that pigeons are sensitive to the conditioned reinforcement that accrues to the stimulus associated with the grea...