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Biasing Temporal Performance of Pigeons and Humans
Abstract and Figures
Interval timing pertains to the ability of organisms to adapt their behavior to the temporal regularity of stimuli such as lights, sounds, or food. Although a set of properties have been established to characterize timing, researchers will encounter phenomena such as temporal distortions, or biases. That is, temporally controlled behaviors may be sensitive to non-temporal variables, such as payoffs (reinforcement probabilities) and base-rates (frequency of stimulus intervals). How timing is affected by these variables in different tasks and species is debatable. In the present dissertation, we discuss these issues throughout four studies investigating how payoff and base-rate affect pigeons and humans in a temporal bisection task. This temporal discrimination task is tested in its standard version – subjects choose one arbitrary key after a short interval sample and another after a long sample (e.g., short—green, long—red) – and a novel version – subjects choose based on location (e.g., short—left, long—right), and their motion is recorded throughout the intervals. While pigeons were placed in either a standard or long operant chamber, human participants were exposed to a standard computer task or a game that required them to move a spaceship horizontally and shoot one of the two aliens at the top corners of the screen. All subjects learned the task and produced a psychometric function (i.e., proportion of “long” responses), characterized by a location (bias) and a scale (sensitivity) parameter. After learning the task, subjects each went through three experimental conditions: Long-Bias, No-Bias, and Short-Bias, indicating the expected effects from the base-rate and payoff manipulations. In general, while bias effects (horizontal shifts of the psychometric functions) were consistent, no significant change was observed in sensitivity to the intervals. The novel task produced stereotypical motion patterns during baseline training – on the long sample trials, subjects approached the short key after sample onset, stayed there for some time, then departed to the long key. During the manipulations, new patterns emerged, especially for the pigeons, and motion was no longer always a good predictor of the proportion of “long”. These results contribute to our understanding of the basic mechanisms involved in interval timing and learning and challenge current timing models to account for competition of stimulus control and new measures of temporal performance, such as motion.
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Animal learning research has increasingly used complex stimuli that approximate natural objects, events, and locations, a trend that has accompanied a resurgence of interest in the role of cognitive factors in learning. Accounts of complex stimulus control have focused mainly on cognitive mechanisms and largely ignored the contribution of stimulus information to perception and memory for complex events. It is argued here that research on animal learning stands to benefit from a more detailed consideration of the stimulus and that James Gibson’s stimulus-centered theory of perception serves as a useful framework for analyses of complex stimuli. Several issues in the field of animal learning and cognition are considered from the Gibsonian perspective on stimuli, including the fundamental problem of defining the effective stimulus.
We investigated how differential payoffs affect temporal discrimination. In a temporal bisection task, pigeons learned to choose one key after a short sample and another key after a long sample. When presented with a range of intermediate samples they produced a Gaussian psychometric function characterized by a location (bias) parameter and a scale (sensitivity) parameter. When one key yielded more reinforcers than the other, the location parameter changed, with the pigeons biasing their choices toward the richer key. We then reproduced the bisection task in a long operant chamber, with choice keys far apart, and tracked the pigeons’ motion patterns during the sample. These patterns were highly stereotypical—on the long sample trials, the pigeons approached the short key at sample onset, stayed there for a while, and then departed to the long key. The distribution of departure times also was biased when the payoff probabilities differed. Moreover, it is likely that temporal control decreased while control by location increased. No evidence was found of changes in temporal sensitivity. The results are consistent with models of timing that take into account bias effects and competition of stimulus control.
Across various subfields within psychology, mechanistic causation is invoked regularly. When the temporal contiguity of the typical cause–effect relation is violated, mechanistic causation often assigns causal roles to mediating hypothetical constructs to account for observed effects. Two primary consequences of mechanistic causation are that 1) the proposed hypothetical constructs add what many behavior analysts consider an unnecessary step in the causal chain, and 2) these constructs then become the focus of study thereafter diverting attention from more accessible “causes.” Constructs do not contribute directly to determining the control of behavior; thus, their reification as “causes” often distracts from variables that do fulfill a causal role. In this review, these consequences are discussed in relation to theories of interval timing proposing an internal clock. Not only has this clock been said to be a cause of behavior in experiments on temporally regulated behavior, but also the clock itself has been a frequent subject of study within the timing literature. Despite descriptive accounts of this sort initially serving a heuristic function for model development, the promotion from descriptive aid to causal factor has the potential to limit much of the heuristic value that mechanistic models of causation can provide to the analysis of behavior. Problems related to construct reification are less likely to be at issue when functional relations and the processes of establishing such behavior are emphasized as alternatives to mechanistic causation alone.
Animals use the neurotransmitter dopamine to encode the relationship between their responses and reward. Reinforcement learning theory ( 1 ) successfully explains the role of phasic bursts of dopamine in terms of future reward maximization. Yet, dopamine clearly plays other roles in shaping behavior that have no obvious relationship to reinforcement learning, including modulating the rate at which our subjective sense of time grows in real time. On page 1273 of this issue, Soares et al. ( 2 ) closely examine the role of dopamine in mice performing a task in which they keep track of the time between two events and make decisions about this temporal duration. The results suggest the need to reassess the leading theory of dopamine function in timing—the dopamine clock hypothesis ( 3 ). They may also help explain empirical phenomena that challenge the reinforcement learning account of dopamine function.
The distribution of latencies and interresponse times (IRTs) of rats was compared between two fixed-interval (FI) schedules of food reinforcement (FI 30 s and FI 90 s), and between two levels of food deprivation. Computational modeling revealed that latencies and IRTs were well described by mixture probability distributions embodying two-state Markov chains. Analysis of these models revealed that only a subset of latencies is sensitive to the periodicity of reinforcement, and prefeeding only reduces the size of this subset. The distribution of IRTs suggests that behavior in FI schedules is organized in bouts that lengthen and ramp up in frequency with proximity to reinforcement. Prefeeding slowed down the lengthening of bouts and increased the time between bouts. When concatenated, latency and IRT models adequately reproduced sigmoidal FI response functions. These findings suggest that behavior in FI schedules fluctuates in and out of schedule control; an account of such fluctuation suggests that timing and motivation are dissociable components of FI performance. These mixture-distribution models also provide novel insights on the motivational, associative, and timing processes expressed in FI performance. These processes may be obscured, however, when performance in timing tasks is analyzed in terms of mean response rates.
J. E. R. Staddon's colleagues and former students discuss Staddon's work as a “theoretical behaviorist” and his influence on their own research.
John Staddon has devoted his long and distinguished career to the study of the adaptive function and mechanisms of learning. He did his graduate work at the famous Skinner Lab at Harvard in the early 1960s (supervised by Richard Herrnstein, who did his doctoral work with B. F. Skinner), but his work can be characterized as theoretical behaviorism. Staddon, now at Duke University, believes that experimental analysis is never enough to make sense of behavior and that “theoretical imagination” is also required. Staddon's theoretical imagination has distinguished his work over the years and has influenced the field. Staddon is not afraid to deviate from the norm: when psychologists were maintaining their distance from behavioral psychology, Staddon was promoting optimality theories. Optimality theories in psychology are now commonplace. In this volume, Staddon's colleagues and former students discuss topics that have been important in his work: behavioral ability and choice, memory, time and models (the subject of his work at Harvard), and behaviorism. They also reflect on Staddon's influence on their own work and the evolution of their thinking on these topics.
ContributorsGiulio Bolacchi, Daniel T. Cerutti, Mircea Ioan Chelaru, J. Mark Cleaveland, Robert H. I. Dale, Rebecca A. Dixon, Valentin Dragoi, Stephen Gray, Jennifer J. Higa, John M. Horner, Nancy K. Innis, Mandar S. Jog, Richard Keen, John E. Kello, Eric Macaux, Armando Machado, John C. Malone, Jr., Kazuchika Manabe, Susan R. Perry, Alliston K. Reid
Bradford Books imprint
Four experiments compared the effects of self-rules and rules, and varied and specific schedules of reinforcement. Participants were first exposed to either several schedules (varied groups) or to one schedule (specific groups) and either were asked to generate rules (self-rule groups), were provided rules (rule groups), or were not asked nor provided rules (control groups). When exposed to FI, sensitivity was greater for the varied than for the specific self-rules and rules groups, regardless of reinforcement rate. Control groups showed intermediate sensitivity levels. When nondifferentiated response rates were obtained, sensitivity for the varied groups was similar to that observed for the specific groups. These results suggest that varied rules promote greater sensitivity than do specific ones as long as variable behavior patterns are obtained.
Interval timing has been widely studied in humans and animals across a variety of different timescales. However, the majority of the literature in this topic has carried the implicit assumption that a mental or neural "clock" receives input and directs output separately from other learning processes. Here we present a review of interval timing as it relates to stimulus control and discuss the role of learning and attention in timing in the context of different experimental procedures. We show that time competes for control over behavior with other processes and suggest that when moving forward with theories of interval timing and general learning mechanisms, the two ought to be integrated.
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. The pigeons received series of three stimuli, one every two seconds: if the three stimuli matched, food was delivered (a win); if they did not match, food was not delivered (a loss). We gave pigeons a choice between two options that provided food with the same probability but they differed in the sequence of stimuli on loss trials. For the near-hit alternative the non-matching stimulus was the third one (defined as a near hit). For the clear-loss alternative the non-matching stimulus was the second one. We found that the pigeons preferred the clear-loss alternative, that is, they preferred to be given information about the outcome sooner. This result is consistent with prior research on suboptimal choice with pigeons that emphasizes the role of information in choice but is inconsistent with the results of research with humans.