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In the Mid-Session Reversal task (MSR), an animal chooses between two options, S1 and S2. Rewards follow S1 but not S2 from trials 1-40, and S2 but not S1 from trials 41-80. With pigeons, the psychometric function relating S1 choice proportion to trial number starts close to 1 and ends close to 0, with indifference (PSE) close to trial 40. Surprisingly, pigeons make anticipatory errors, choosing S2 before trial 41, and perseverative errors, choosing S1 after trial 40. These errors suggest that they use time into the session as the preference reversal cue. We tested this timing hypothesis with 10 Spotless starlings. After learning the MSR task with a T-s Inter-Trial Interval (ITI), they were exposed to either 2 T or T/2 ITIs during testing. Doubling the ITI should shift the psychometric function to the left and halve its PSE, whereas halving the ITI should shift the function to the right and double its PSE. When the starlings received one pellet per reward, the ITI manipulation was effective: The psychometric functions shifted in the direction and by the amount predicted by the timing hypothesis. However, non-temporal cues also influenced choice. published

In a variety of laboratory preparations, several animal species prefer signaled over unsignaled outcomes. Here we examine whether pigeons prefer options that signal the delay to impending reward over options that do not and how this preference changes with the ratio of the delays. We offered pigeons repeated choices between two alternatives leading to a short or a long delay to reward. For one alternative (informative), the short and long delays were reliably signaled by different stimuli (e.g. SS for short delays, SL for long delays). For the other (non-informative), the delays were not reliably signaled by the stimuli presented (S1 and S2). Across conditions, we varied the durations of the short and long delays while keeping the average delay to reward constant. Pigeons preferred the informative over the non-informative option and this preference became stronger as the ratio of the long to the short delay increased. A modified version of the Δ-Σ hypothesis (González et al., 2020a) incorporating a contrast-like process between the immediacies to reward signaled by each stimulus accounted well for our findings. Functionally, we argue that a preference for signaled delays hinges on the potential instrumental advantage typically conveyed by information.

We used a midsession reversal task to investigate how temporal and situational cues may combine to determine choice in frequently changing environments. Pigeons learned a simultaneous discrimination with 2 stimuli: S1 and S2. Choices of S1 were reinforced only during the first trials, and choices of S2 were reinforced only during the last trials of the session, that is, the reinforcement contingencies reversed once during the session. To weaken the temporal cue (time into the session) that signaled the reversal trial, we varied the location of reversal trial randomly across sessions; to weaken the situational cue (the outcome of the previous trials that might support a win-stay/loose shift strategy), we varied the payoff probabilities associated with S1 and S2. Performance was consistent neither with the exclusive use of a timing strategy, nor with the exclusive use of a situational, win-stay/lose-shift strategy. Instead, choice seemed to be under joint control of both cues. The relative influence of these cues was dynamic: When payoff was higher for S1 than S2, behavior was less time-controlled than when the payoff was higher for S2 that S1, or when they were equal. We advance a descriptive mixture model of joint control for the midsession reversal task. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

In the study of animal timing over the last 100 years, we identify three different periods, each characterized by a distinct activity. In the first period, researchers brought timing into the laboratory and explored its multiple expressions empirically. In the second period, the growing body of empirical findings inspired researchers to develop a plethora of timing models that vary in theoretical orientation, scope, depth, and quantitative explicitness. We argue that it is now the time to advance towards a third period, wherein researchers select models by comparing them with one another and with data. We make our case by contrasting how the scalar expectancy theory and the learning-to-time model conceive of temporal memory and learning both in concurrent timing tasks and in retrospective timing tasks. We identify four problems related to the structure of temporal memory and to the rules of temporal learning that challenge these models and that should drive the next steps in modeling the timing abilities of animals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Our goal was to assess the role of timing in pigeons' performance in the midsession reversal task. In discrete-trial sessions, pigeons learned to discriminate between 2 stimuli, S1 and S2. Choices of S1 were reinforced only in the first half of the session and choices of S2 were reinforced only in the second half. Typically, pigeons choose S2 before the contingency reverses (anticipatory errors) and S1 after (perseverative errors), suggesting that they time the interval from the beginning of the session to the contingency reversal. To test this hypothesis, we exposed pigeons to a midsession reversal task and, depending on the group, either increased or decreased the ITI duration. We then contrasted the pigeons' performance with the predictions of the Learning-to-Time (LeT) model: In both conditions, preference was expected to reverse at the same time as in the previous sessions. When the ITI was doubled, pigeons' preference reversal occurred at half the trial number but at the same time as in the previous sessions. When the ITI was halved, pigeons' preference reversal occurred at a later trial but at an earlier time than in the previous sessions. Hence, pigeons' performance was only partially consistent with the predictions of LeT, suggesting that besides timing, other sources of control, such as the outcome of previous trials, seem to influence choice.

In a concurrent-chain procedure, pigeons choose between 2 initial-link stimuli; one is followed by terminal link stimuli that signal reliably whether food will be delivered after a delay; the other is followed by terminal link stimuli that do not signal whether food will be delivered after the delay. Pigeons prefer the former alternative even when it yields a lower overall probability of food. Recently, we proposed the Delta-Sigma (∆-∑) hypothesis to explain the effect: Preference depends on the difference (∆) between the reinforcement probabilities associated with the terminal link stimuli, and the overall probability of reinforcement (∑) associated with the alternative. The hypothesis predicts that, for constant ∑, animals should prefer alternatives with greater ∆ values regardless of the specific probabilities of reinforcement that determine ∆. In 2 experiments, we tested this prediction by comparing a ∆ = .5 against a ∆ = 0 alternative, with the former obtained with different pairs of reinforcement probabilities across conditions. The results supported the hypothesis when the 2 probabilities defining ∆ were significantly greater than 0, but not when one of them was close to 0. The results challenge our theoretical accounts of suboptimal choice and the variables considered to determine pigeons' preference.

When given a choice between two alternatives, each offering food after the same delay with different but signaled probabilities, pigeons often prefer the low probability alternative. This preference is surprising because pigeons fail to maximize the rate of food intake; they exhibit a suboptimal preference. We advance a new explanation, the Δ-∑ hypothesis, in which the difference in probability of reinforcement within terminal links (Δ) and the overall reinforcement probability rate of each alternative (∑) are the key variables responsible for such suboptimal preference. We tested the Δ-∑ hypothesis in two experiments. In Experiment 1, we manipulated the Δs while maintaining constant all other parameters of the task, in particular the ∑s. We predicted a preference for the alternative with the larger Δ. In Experiment 2, we examined the effect of the overall reinforcement probabilities, the ∑s, while maintaining constant all other parameters of the task, in particular the Δs. We predicted a preference for the larger ∑. The results of both experiments support the Δ-∑ hypothesis.

We investigated how base rates 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 psychometric function characterized by a bias and a scale parameter. When one of the trained samples was more frequent than the other, only the location parameter changed, with the pigeons biasing their choices toward the key associated with the most frequent sample. 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. Pigeons learned to approach the short key following sample onset, wait on the "short side" for a few seconds, and then, when the sample continued, depart toward the long key. This time-place curve was affected by sample base rate: The probability of pigeons going directly to the long side after sample onset increased when long samples were more frequent than short samples, indicating a decrease of temporal control. We found no evidence of changes in temporal sensitivity. The results are most consistent with models of timing that take into account biasing effects and competition for stimulus control. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The present article traces the development of Timberlake’s behavior systems framework while noting connections between it and Kantor’s interbehavioral psychology. Congruent with Timberlake’s behavior systems approach, interbehaviorists assert that (a) behavior is best understood as part of a complex causal system instead of a simple linear model, (b) the study of learning and behavior analysis should consist of the study of multiple responses and the systematic observation of response forms, (c) learning involves the reorganization of a behavior system, (d) behavioral analyses should be more ecological in orientation, and (e) psychology would benefit from a set of methodologies and apparatuses broader than those normally used to study operant and Pavlovian conditioning. These connections may derive from two broad themes shared by the behavior systems framework and interbehavioral psychology: an appreciation for a systems view of behavior and the importance of ethological considerations.

Eckard and Lattal (2020) summarized the behavioristic view of hypothetical constructs and theories, and then, in a novel and timely manner, applied this view to a critique of internal clock models of temporal control. In our three-part commentary, we aim to contribute to the authors’ discussion by first expanding upon their view of the positive contributions afforded by constructs and theories. We then refine and question their view of the perils of reifying constructs and assigning them causal properties. Finally, we suggest to behavior analysts four rules of conduct for dealing with mediational theories: tolerate constructs proposed with sufficient reason; consider them seriously, both empirically and conceptually; develop alternative, behavior-analytic models with overlapping empirical domains; and contrast the various models. Through variation and selection, behavioral science will evolve.

In the suboptimal-choice task, birds systematically choose the leaner but informative option (suboptimal) over the richer but non-informative option (optimal). The task has two variations. In the standard task, the optimal option includes two terminal link stimuli. In the original task, it includes a single terminal link stimulus. Two models, the temporal information account (Cunningham and Shahan, J Exp Psychol Anim Learn Cogn 44:1-22, 2018) and the ∆-∑ hypothesis (Gonzalez et al., J Exp Anal Behav 113:591-608, 2020), presuppose that these procedures are equivalent, but no formal comparison is available. Here we test whether or not these procedures are functionally equivalent. One group of pigeons was trained with the standard procedure, another group with the original procedure, and a third group was trained with a hybrid of the other two (i.e., the two options were the optimal links of the standard and original procedures). Our findings indicate that the number of terminal link stimuli in the optimal option is inconsequential vis-a-vis choice. Moreover, our findings also indicate that latencies to respond are a sensitive metric of value and choice. As predicted by the Sequential Choice Model, we were able to predict simultaneous choices from the latencies of sequential choices and observed a substantial shortening of latencies during simultaneous choices.

Using signal detection theory, we investigated whether human participants represent time linearly or logarithmically in a bisection task. Participants saw a stimulus 1.0 to 1.5 s in duration, and then judged whether the stimulus duration was closer to 1.0 s or to 1.5 s, and how sure they were of their response. Whereas the mean of the subjective stimulus duration was a linear function of the objective stimulus duration, participants produced remarkably different psychophysical functions-linear for some participants, concave for others, and convex for still others. Hence, the appropriate question might not be whether humans encode time linearly or logarithmically, but for which participants and under which conditions is time encoded linearly, logarithmically, or even exponentially. (PsycINFO Database Record (c) 2018 APA, all rights reserved). 44

We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function.

We investigated how differential payoffs affect the temporal discrimination of humans. In a temporal bisection task, participants learned to make one response after a short sample and another after a long sample. When presented with a range of intermediate samples, the proportion of responses fitted well a Gaussian-like distribution function characterized by a location (bias), a scale (sensitivity) parameter, and two asymptote (discrimination) parameters. In Experiment 1, when one response yielded more reinforcers than the other, parameters were unaltered, but overall responses increased for the response producing higher payoffs. In Experiment 2, we used a video game to track motion during the sample and participants learned to approach the “short” response location at sample onset and remain there before departing to the “long” location on long trials. Departure times were shorter when “long” choices produced higher payoffs than “short” and matched well the shifted psychometric functions. However, on some trials, subjects were biased for short, returning to the short side after having departed towards long. Evidence was found for effects of differential payoffs on response bias, but discrimination and sensitivity did not change consistently. These results favor a behavioral account of timing processes.

A meaningless symbol that repeatedly co-occurs with emotionally salient faces (US) can transform into a valenced symbol (CS). US-to-CS valence transformations have been observed for CS that have been directly (US→CS0) and indirectly (US→CS0→CS1→CS2) linked with face US. The structure of a US→CS0→CS1→CS2 series may be conceptualized in terms of “nodal distance,” where CS0, CS1, and CS2 are 0, 1, and 2 nodes from the US respectively. Increasing nodal distance between an evaluated CS and its linked US can reduce magnitude of observed CS valence transformations. We explored currently whether nodal distance can influence CS valence extinction, which describes reductions in CS valence following repeated exposures to CS without any accompanying US. In our study, faces with happy/neutral/sad expressions (US) were directly linked with nonsense words (US→CS0). The directly linked CS0 was concurrently linked with other words (CS0→CS1, CS1→CS2). Subjects evaluated all stimuli before and after conditioning, then continued to provide CS evaluations twice a week for 6 weeks. Bayesian factors provided credible evidence for the transformation and extinction of CS valences that were 0 and 1 nodes from US (all BF10’s > 100). The variability across post-conditioning CS evaluations provides indirect evidence for context-sensitive/propositional and structural/associative operations during CS evaluations.

Simple and conditional discrimination training may produce various types of controlling relations. Responses may be controlled primarily by the positive stimulus (select-control relation) or by the negative stimulus (reject-control relation; the subject excludes the negative stimulus and chooses the positive). Bees learn to respond in simple and conditional discriminations. However, no study has searched for reject-control responding in Melipona bees. We trained Melipona quadrifasciata on a simple discrimination task (S+ vs. S-; e.g., blue vs. yellow) and then probed for stimulus control with two types of probe trials, S+ versus a new stimulus (Select-control probes) and S- versus a new stimulus (Reject-control probes). For Group Different, a new-stimulus color (e.g., white) was used in one type of probe and another color (e.g., black) was used in the other type. For Group Same, a single new-stimulus color was used in both types of probes. On Select probes, the bees always preferred S+ to the new stimulus. On Reject probes, results were mixed. Depending on the colors used in training and probing, bees responded to both stimuli, and even preferred the S-. The data suggest no control by the negative function of the S- and support the select-stimulus control hypothesis of responding.

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. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Eckard and Lattal (2020) summarized the behavioristic view of hypothetical constructs and theories, and then, in a novel and timely manner, applied this view to a critique of internal clock models of temporal control. In our three-part commentary, we aim to contribute to the authors' discussion by first expanding upon their view of the positive contributions afforded by constructs and theories. We then refine and question their view of the perils of reifying constructs and assigning them causal properties. Finally, we suggest to behavior analysts four rules of conduct for dealing with mediational theories: tolerate constructs proposed with sufficient reason; consider them seriously, both empirically and conceptually; develop alternative, behavior-analytic models with overlapping empirical domains; and contrast the various models. Through variation and selection, behavioral science will evolve.

O presente documento constitui um relato teoricamente fundamentado da atividade desenvolvida enquanto estudante estagiário na Escola Secundária Inês de Castro, no âmbito da iniciação à prática profissional (Decreto-Lei n.º 79/2014 de 14 de maio). Este relatório consiste na descrição e análise dos acontecimentos importantes vividos ao longo deste ano letivo, responsáveis pela construção da identidade pessoal e profissional do futuro docente. N/A

Researchers have unraveled multiple cases in which behavior deviates from rationality principles. We propose that such deviations are valuable tools to understand the adaptive significance of the underpinning mechanisms. To illustrate, we discuss in detail an experimental protocol in which animals systematically incur substantial foraging losses by preferring a lean but informative option over a rich but non-informative one. To understand how adaptive mechanisms may fail to maximize food intake, we review a model inspired by optimal foraging principles that reconciles sub-optimal choice with the view that current behavioral mechanisms were pruned by the optimizing action of natural selection. To move beyond retrospective speculation, we then review critical tests of the model, regarding both its assumptions and its (sometimes counterintuitive) predictions, all of which have been upheld. The overall contention is that (a) known mechanisms can be used to develop better ultimate accounts and that (b) to understand why mechanisms that generate suboptimal behavior evolved, we need to consider their adaptive value in the animal’s characteristic ecology.

We examined how biasing time perception affects choice in a midsession reversal task. Given a simultaneous discrimination between stimuli S1 and S2, with choices of S1 reinforced during the first, but not the second half of the trials, and choices of S2 reinforced during the second, but not the first half of the trials, pigeons show anticipation errors (premature choices of S2) and perseveration errors (belated choices of S1). This suggests that choice depends on timing processes, on predicting when the contingency reverses based on session duration. We exposed 7 pigeons to a midsession reversal task and manipulated the reinforcement rate on each half of the session. Compared to equal reinforcement rates on both halves of the session, when the reinforcement rate on the first half was lower than on the second half, performance showed more anticipation and less perseveration errors, and when the reinforcement rate on the first half was higher than on the second half, performance showed a remarkable reduction of both types of errors. These results suggest that choice depends on both time into the session and the outcome of previous trials. They also challenge current models of timing to integrate local effects.

When offered a choice between 2 alternatives, animals sometimes prefer the option yielding less food. For instance, pigeons and starlings prefer an option that on 20% of the trials presents a stimulus always followed by food, and on the remaining 80% of the trials presents a stimulus never followed by food (the Informative Option), over an option that provides food on 50% of the trials regardless of the stimulus presented (the Noninformative Option). To explain this suboptimal behavior, it has been hypothesized that animals ignore (or do not engage with) the stimulus that is never followed by food in the Informative Option. To assess when pigeons attend to the stimulus usually not followed by food, we increased the probability of reinforcement, p, in the presence of that stimulus. Across 2 experiments, we found that the value of the Informative Option decreased with p. To account for the results, we added to the Reinforcement Rate Model (and also to the Hyperbolic Discounting Model) an engagement function, f(p), that specified the likelihood the animal attends to a stimulus followed by reward with probability p, and then derived the model predictions for 2 forms of f(p), a linear function, and an all-or-none threshold function. Both models predicted the observed findings with a linear engagement function: The higher the probability of reinforcement after a stimulus, the higher the probability of engaging the stimulus, and, surprisingly, the less the value of the option comprising the stimulus., This study was conducted at the Psychology Research Centre (UID/PSI/01662/2013) of the University of Minho, and supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Science, Technology and Higher Education through national funds and cofinanced by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653). This work was also supported by an FCT Grant (PTDC/MHC-PCN/3540/2012) to AM. IF and CP were supported by FCT Doctoral Grants (SFRH/BD/77061/2011 and SFRH/BD/78566/2011, respectively).

We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function.

To investigate the coding strategies that pigeons may use in a temporal discrimination tasks, pigeons were trained on a matching-to-sample procedure with three sample durations (2s, 6s and 18s) and two comparisons (red and green hues). One comparison was correct following 2-s samples and the other was correct following both 6-s and 18-s samples. Tests were then run to contrast the predictions of two hypotheses concerning the pigeons’ coding strategies, the multiple-coding and the single-code/default. According to the multiple-coding hypothesis, three response rules are acquired, one for each sample. According to the single-code/default hypothesis, only two response rules are acquired, one for the 2-s sample and a “default” rule for any other duration. In retention interval tests, pigeons preferred the “default” key, a result predicted by the single-code/default hypothesis. In no-sample tests, pigeons preferred the key associated with the 2-s sample, a result predicted by multiple-coding. Finally, in generalization tests, when the sample duration equaled 3.5s, the geometric mean of 2s and 6s, pigeons preferred the key associated with the 6-s and 18-s samples, a result predicted by the single-code/default hypothesis. The pattern of results suggests the need for models that take into account multiple sources of stimulus control.

In the natural environment, when an animal encounters a stimulus that signals the absence of food-a 'bad-news' stimulus-it will most likely redirect its search to another patch or prey. Because the animal does not pay the opportunity cost of waiting in the presence of a bad-news stimulus, the properties of the stimulus (e.g., its duration and probability) may have little impact in the evolution of the decision processes deployed in these circumstances. Hence, in the laboratory, when animals are forced to experience a bad-news stimulus they seem to ignore its duration, even though they pay the cost of waiting. Under certain circumstances, this insensitivity to the opportunity cost can lead to suboptimal preferences, such as a preference for an option yielding a low rather than a high rate of reinforcement. In 2 experiments, we tested Vasconcelos, Monteiro, and Kacelnik's (2015) assumption that, if given the opportunity, animals will escape the bad-news stimulus. To predict when an escape response should occur, we incorporated ideas from the prey choice model into Vasconcelos et al. (2015) model and made 2 novel predictions. Namely, both longer intertrial intervals and longer durations of signals predicting food or no food should lead to higher proportions of escape responses. The results of 2 experiments with pigeons supported these predictions., This study was conducted at the Psychology Research Centre, University of Minho, Portugal, and was supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Education and Science through national funds cofinanced by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013). This work was also supported by FCT Grant PTDC/MHC-PCN/3540/2012 to Armando Machado. Ines Fortes was supported by FCT Doctoral Grant (SFRH/BD/77061/2011). We thank the members of the Animal Learning and Behavior Laboratory of University of Minho for their comments on a prior version of this paper., info:eu-repo/semantics/publishedVersion

The temporal bisection task, one of the most widely used to study time perception, has helped to understand the psychophysics of time and the mechanisms of timing across different species. We extended the temporal bisection task to dogs. Five dogs were reinforced for choosing a yellow but not a blue stimulus after a 1-s tone, and for choosing a blue but not a yellow stimulus after a 4-s tone. After they learned this conditional discrimination, the dogs chose between the blue and yellow stimuli after tones with intermediate durations (1.4, 2.0, and 2.8 s). The results showed that the proportion of “Long” choices increased monotonically with stimulus duration. Moreover, the point of subjective equality was slightly below the geometric mean of the trained tone durations. These psychophysical results are consistent with those obtained with other nonhuman species, and suggest that common mechanisms underlie timing across different mammals and birds., This research was part of the scientific program of Instituto Nacional de Ciência e Tecnologia Sobre Comportamento, Cognição e Ensino, with support from the Brazilian National Research Council (CNPq, Grant 465686/2014-1) and the São Paulo Research Foundation (Grant 2014/50909-8). Camila Domeniconi had a postdoctoral fellowship from the Foundation for Research Support in the State of São Paulo (FAPESP, 2009/ 18479-5). She has a research productivity fellowship bythe National Council for Scientific and Technological Development (CNPq, 301623/2012-0). Armando Machado was supported by grant PTDC/MHC-PCN/ 3540/ 2012 from the Portuguese Foundation for Science and Technology., info:eu-repo/semantics/publishedVersion

The ability to identify stimuli that signal important events is fundamental for an organism to adapt to its environment. In the present paper, we investigated how more than one stimulus could be used jointly to learn a temporal discrimination task. Ten pigeons were exposed to a symbolic matching-to-sample procedure with three durations as samples (2, 6, and 18 s of keylight) and two colors as comparisons (red and green hues). A 30-s intertrial interval (ITI), illuminated with a houselight, separated the trials. Both the houselight and the sample keylight could control responding, so two tests were run to assess how these stimuli influenced choice. In the no-sample test, the keylight was not presented; in the dark-ITI test, the houselight was not illuminated. Results suggest that both houselight and keylight controlled choice, and with the exception of one animal, the more a pigeon relied on one of these stimuli, the less it appeared to rely on the other., The present work was conducted at the Psychology Research Centre, University of Minho, and was supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Education and Science through national funds and when applicable co-financed by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013). This work was also supported by FCT Doctoral Grants to Carlos Pinto (SFRH/BD/78566/2011) and Ines Fortes (SFRH/BD/77061/2011), and a FCT Grant (PTDC/MHC-PCN/3540/2012) to Armando Machado., info:eu-repo/semantics/publishedVersion

Responding by exclusion, one of the most robust phenomena in Experimental Psychology, describes a particular form of responding observed in symbolic, matching-to-sample tasks. Given two comparison stimuli, one experimentally defined and one experimentally undefined, the participant prefers the undefined comparison following an undefined sample. The goal of the present study was to determine whether responding by exclusion could be obtained using samples that varied along a single dimension. Using a double temporal bisection task, 10 university students learned to choose visual comparisons (colored circles) based on the duration of a tone. In tests of exclusion, sample stimuli with new durations were followed by comparison sets that included one previously trained, defined comparison (colored circle) and one previously untrained, undefined comparison (geometric shape). Participants preferred the defined comparisons following the defined samples and the undefined comparisons following the undefined samples, the choice pattern typical of responding by exclusion. The use of samples varying along a single dimension allows us to study the interaction between stimulus generalization gradients and exclusion in the control of conditional responding.

To test the Learning-to-Time model, six pigeons learned two temporal bisection tasks. In one task they learned to choose a Red key over a Green key following 2-s samples and the Green key over the Red key following 6-s samples; in another task, they learned to choose a Blue key over a Yellow key following 6-s samples and the Yellow key over the Blue key following 18-s samples. After each task was learned, temporal generalization gradients were obtained with samples ranging from 0.7 s to 51.4 s. Finally, preference for Green over Blue - the keys associated with the common 6-s duration, was determined as a function of sample duration. Two issues were examined, whether the preference for Green over Blue increased with sample duration, a transposition-like effect reported before, and whether the preference for Green over Blue could be predicted from the generalization gradients for Green and Blue previously obtained. Results showed that preference for Green over Blue increased with sample duration and that the general shape of the function could be predicted from the generalization gradients. The Learning-to-Time model accounted well for the major trends in the data., The authors thank Saulo Missiaggia Velasco for all the valuable help given during the data collection at the University of Sao Paulo. The authors also thank the students from the Animal Learning and Behavior laboratory of the University of Minho for their helpful comments on the paper. Ana Catarina Vieira de Castro was supported by a PhD fellowship and Armando Machado by a grant from the Portuguese Foundation for Science and Technology (FCT). Gerson Yukio Tomanari was supported by a grant from the Brazilian National Council for Science and Technology (CNPq)., info:eu-repo/semantics/publishedVersion

Inspired by Spence's seminal work on transposition, we propose a synthetic approach to understanding the temporal control of operant behavior. The approach takes as primitives the temporal generalization gradients obtained in prototypical concurrent and retrospective timing tasks and then combines them to synthetize more complex temporal performances. The approach is instantiated by the learning-to-time (LeT) model. The article is divided into three parts. In the first part, we review the basic findings concerning the generalization gradients observed in fixed-interval schedules, the peak procedure, and the temporal generalization procedure and then describe how LeT explains them. In the second part, we use LeT to derive by gradient combination the typical performances observed in mixed fixed-interval schedules, the free-operant psychophysical procedure, the temporal bisection task, and the double temporal bisection task. We also show how the model plays the role of a useful null hypothesis to examine whether temporal control in the bisection task is relative or absolute. In the third part, we identify a set of issues that must be solved to advance our understanding of temporal control, including the shape of the generalization gradients outside the range of trained stimulus durations, the nature of temporal memories, the influence of context on temporal learning, whether temporal control can be inhibitory, and whether temporal control is also relational. These issues attest to the heuristic value of a Spencean approach to temporal control., The authors MPC, AM, and MV were supported by grants SFRH/BD/73875/2010, PTDC/MHC-PCN/3540/2012, and IF/01624/2013/CP1158/CT0012, respectively, from the Portuguese Foundation for Science and Technology. This study was conducted at the Psychology Research Centre, University of Minho, and partially supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and when applicable co-financed by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013)., info:eu-repo/semantics/publishedVersion

In temporal discriminations tasks, more than one stimulus may function as a time marker. We studied two of them in a matching-to-sample task, the sample keylight and the houselight that signaled the intertrial interval (ITI). One group of pigeons learned a symmetrical matching-to-sample task with two samples (2 s or 18 s of a center keylight) and two comparisons (red and green side keys), whereas another group of pigeons learned an asymmetrical matching-to-sample task with three samples (2 s, 6 s, and 18 s) and two comparisons (red and green). In the asymmetrical task, 6-s and 18-s samples shared the same comparison. In a subsequent retention test, both groups showed a preference for the comparison associated with the longer samples, a result consistent with the hypothesis that pigeons based their choices on the duration elapsed since the offset of the houselight (i.e., sample duration + retention interval). Results from two no-sample tests further corroborated the importance of the ITI illumination as a time marker: When the ITI was illuminated, the proportion of choices correlated positively with the retention interval; when the ITI was darkened, choices fell to random levels. However, the absolute value of choice proportions suggested that the sample stimulus was also a time marker. How multiple stimuli acquire control over behavior and how they combine remains to be worked out., This work was conducted at the Psychology Research Centre, University of Minho, and was supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Education and Science through national funds, and when applicable co-financed by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013). This work was also supported by a FCT Doctoral Grant (SFRH/BD/78566/2011) to Carlos Pinto and a FCT Grant (PTDC/MHC-PCN/3540/2012) to Armando Machado., info:eu-repo/semantics/publishedVersion

Several studies have shown that, when offered a choice between an option followed by stimuli indicating whether or not reward is forthcoming and an option followed by noninformative stimuli, animals strongly prefer the former even when the latter is more profitable. Though this paradoxical preference appears to question the principles of optimal foraging theory, Vasconcelos, Monteiro, and Kacelnik (2015) proposed an optimality model that shows how such preference maximizes gains under certain conditions. In this paper, we tested the model's core assumption that a stimulus signaling the absence of food should not influence choice independently of its other properties, such as probability or duration. In 2 experiments, pigeons chose between 2 options: the "informative option" delivered food on 20% of the trials after a 10-s delay, signaled by a "good-news" stimulus, and delivered no food on the remaining 80% of the trials, signaled by a "bad-news" stimulus. The "noninformative option" delivered food after 10 s on 50% of the trials, regardless of the signal shown. In Experiment 1, the probability of the bad-news stimulus was manipulated from 0.80 to 1.00; in Experiment 2, the duration of the bad-news stimulus was increased every time pigeons preferred the informative option, reaching at least 200 s. Consistent with the model's predictions, pigeons clearly preferred the informative option even when the noninformative option delivered 9 (Experiment 1) and 35 (Experiment 2) times more food., This study was conducted at the Psychology Research Centre, University of Minho, Portugal, and was supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Education and Science through national funds cofinanced by FEDER under the PT2020 Partnership Agreement (Grant UID/PSI/01662/2013). This work was also supported by FCT Grant PTDC/MHC-PCN/3540/2012 to Armando Machado. Ines Fortes and Marco Vasconcelos were supported by an FCT Doctoral Grant SFRH/BD/77061/2011 and an FCT Investigator Grant IF/01624/2013, respectively. We are grateful to Thomas Zentall and the members of the Animal Learning and Behavior Laboratory of University of Minho for their helpful comments on a prior version of this paper., info:eu-repo/semantics/publishedVersion

We examined whether temporal learning in a bisection task is absolute or relational. Eight pigeons learned to choose a red key after a t-seconds sample and a green key after a 3t-seconds sample. To determine whether they had learned a relative mapping (short -> Red, long -> Green) or an absolute mapping (t-seconds -> Red, 3t-seconds -> Green), the pigeons then learned a series of new discriminations in which either the relative or the absolute mapping was maintained. Results showed that the generalization gradient obtained at the end of a discrimination predicted the pattern of choices made during the first session of a new discrimination. Moreover, most acquisition curves and generalization gradients were consistent with the predictions of the learning-to-time model, a Spencean model that instantiates absolute learning with temporal generalization. In the bisection task, the basis of temporal discrimination seems to be absolute, not relational., The authors were supported by grants from the Portuguese Foundation for Science and Technology (FCT SFRH/BD/73875/2010 and PTDC/MHC-PCN/3540/2012). The study was conducted at the Psychology Research Centre of the University of Minho, and was partially supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and cofinanced by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013). The authors thank Catarina Soares and Margarida Monteiro for helping with data collection, and the members of the Animal Learning and Behavior Lab for comments on a first version of the manuscript. Results reported here were presented at the 26th Meeting of the Spanish Society for Comparative Psychology, Braga, Portugal, and at the 2014 Annual Symposium of the Society for the Quantitative Analysis of Behavior, Chicago, Illinois., info:eu-repo/semantics/publishedVersion

[Excerpt] Barba’s (2012) article deftly weaves three main themes in one argument about operant variability. From general theoretical considerations on operant behavior (Catania, 1973), Barba derives methodological guidelines about response differentiation and applies them to the study of operant variability. In the process, he uncovers unnoticed features of operant variability research (e.g., Neuringer, 2002) and proposes interesting modifications and extensions of current experimental practices. Barba’s article calls for renewed attention to important issues, and we find merit in his proposal to evaluate operant variability by comparing response distributions along a common continuous measure. We are less convinced, however, by the conceptual underpinnings that he brings to the task. [...]

We investigated the effects of interdimensional discrimination training in the temporal generalization gradient. In a matching-to-sample task, pigeons learned to choose key S after a T-s houselight sample and key NS in the absence of the houselight sample. For one group of pigeons, T = 20 s; for another, T = 10 s. Subsequently, houselight duration was varied to obtain temporal generalization gradients. Results showed that (a) proportion S increased as houselight duration ranged from 0 s to T s and then remained high for houselight durations longer than T; (b) the gradients were well described by negative-exponential functions; (c) these non-flat gradients were present from the beginning of testing, and; (d) the average gradients obtained with T = 20 s and T = 10 s overlapped when plotted in relative time. We conclude that temporal control does not require explicit discrimination training along the temporal dimension, and that temporal generalization gradients obtained with an interdimensional protocol show the scalar property of timing. We discuss how these findings challenge current models of timing., This work was supported by Portuguese Foundation for Science and Technology (FCT) [Grant number PTDC/MHC-PCN/3540/2012] to Armando Machado. Ana Catarina Vieira de Castro was supported by an FCT doctoral grant [Grant number SFRH/BD/43398/2008], by ERDF funds through the Operational Competitiveness Programme-COMPETE, and by National Funds through FCT under project FCOMP-01-0124-FEDER-029527 [Grant number PTDC/MHC ETI/4890/2012], and Marco Vasconcelos was supported by an FCT Investigator Grant [Grant number IF/01624/2013]., info:eu-repo/semantics/publishedVersion

To better understand short-term memory for temporal intervals, we re-examined the choose-short effect. In Experiment 1, to contrast the predictions of two models of this effect, the subjective shortening and the coding models, pigeons were exposed to a delayed matching-to-sample task with three sample durations (2, 6 and 18 s) and retention intervals ranging from 0 to 20 s. Consistent with the coding model, the results suggested a sudden forgetting of memories for duration. In Experiment 2, to test the confusion hypothesis, the characteristics of the ITI and the retention interval differed. Contrary to the confusion hypothesis, a choose-short effect was obtained. In both experiments, a test with only two of the three comparison keys was performed. The results suggest three effects that may be controlling the birds’ responses: stimulus generalization when no retention interval is present; an increase in random responding at longer retention intervals; and, similarly, an increase in preference for the “short-sample” key at longer retention intervals.

We present an elementary proof of the existence of an eigenvalue for an endomorphism of a complex vector space and we derive the Fundamental Theorem of Algebra as a corollary of this existence. We also present new proofs for the corresponding results for endomorphisms of real vector spaces.

Pigeons were trained on two temporal bisection tasks, which alternated every two sessions. In the first task, they learned to choose a red key after a 1-s signal and a green key after a 4-s signal; in the second task, they learned to choose a blue key after a 4-s signal and a yellow key after a 16-s signal. Then the pigeons were exposed to a series of test trials in order to contrast two timing models, Learning-to-Time (LeT) and Scalar Expectancy Theory (SET). The models made substantially different predictions particularly for the test trials in which the sample duration ranged from 1 s to 16 s and the choice keys were Green and Blue, the keys associated with the same 4-s samples: LeT predicted that preference for Green should increase with sample duration, a context effect, but SET predicted that preference for Green should not vary with sample duration. The results were consistent with LeT. The present study adds to the literature the finding that the context effect occurs even when the two basic discriminations are never combined in the same session., Research was supported by a grant from the Portuguese Foundation for Science and Technology (FCT) to Armando Machado. Joana Arantes was supported by a Ph.D. scholarship from the Portuguese Foundation for Science and Technology (FCT). We thank John Staddon, Randolph Grace, and Luı´s Oliveira for helpful comments on earlier versions of the paper, and Alexandra Lima for assistance with data collection., info:eu-repo/semantics/publishedVersion

The primary goal was to compare results from a free-operant procedure with pigeons [Machado, A., Guilhardi, P., 2000. Shifts in the psychometric function and their implications for models of timing. J. Exp. Anal. Behav. 74, 25-54, Experiment 2] with new results obtained with rats. The secondary goal was to compare the results of both experiments with dependent variables that were not used in the original publication. As in the original study with pigeons, rats were trained on a two-alternative free-operant psychophysical procedure in which left lever press responses were reinforced during the first and second quarters of a 60-s trial, and right lever press responses were reinforced during the third and fourth quarters of the trial. The quarters were reinforced according to four independent variable interval (VI) schedules of reinforcement. The VI duration was manipulated in each quarter, and shifts in the psychophysical functions that relate response rate with time since trial onset were measured. The results obtained with rats were consistent with those previously obtained with pigeons. In addition, results not originally reported were also consistent between rats and pigeons, and provided insights into the perception, memory, and decision processes in Scalar Expectancy Theory and Learning-to-Time Theory., Uminho - Universidade do Minho(MH44234), This research was supported by National Institute of Mental Health Grant MH44234 to Brown University, and by a Research Grant from the Portuguese Science and Technology Foundation to Universidade do Minho. The authors thank. An Le for conversion of the primary data into compatible format., info:eu-repo/semantics/publishedVersion

We examined whether temporal context influences how animals produce a time interval. Six pigeons pecked one key to start an interval and then another key to end the interval. Reinforcement followed whenever the interval duration fell within a range of values signaled by the keylight colors. During Phase 1, keylight colors S1 and L1, intermixed across trials, signaled the ranges (0.5-1.5 s) and (1.5- 4.5 s), respectively. During Phase 2, colors S2 and L2 signaled the ranges (1.5-4.5 s) and (4.5-13.5 s), respectively. We asked whether the intervals produced in the presence of L1 and S2, stimuli signalling the same range, varied with their temporal context, short in Phase 1, long in Phase 2. The results showed that a) the intervals produced in the presence of the different keylight colors accorded with the main properties of temporal differentiation, including Weber’s law, b) the L1 intervals had slightly higher means than the S2 intervals, a weak contrast effect, c) the L1 intervals also had higher variability than the S2 intervals. An extension of the learning-to-time model to temporal differentiation tasks reproduced some of the major features of the data but left unanswered how context might change the model parameters., MPC, AM, and MV benefited from grants from the Portuguese Foundation for Science and Technology (FCT SFRH/BD/73875/2010, PTDC/MHC-PCN/3540/2012, and IF/01624/2013/CP1158/CT0012, respectively). This study was conducted at the Psychology Research Centre, University of Minho, and partially supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds and when applicable co-financed by FEDER under the PT2020 Partnership Agreement (UID/PSI/01662/2013). The authors thank Catarina Soares, Margarida Monteiro, Francisca Cunha, Janete Silva, Lénia Amaral, Pilar Niño and Sofia Ribeiro for help collecting data., info:eu-repo/semantics/publishedVersion