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To understand how effort, defined by number of responses required to obtain a reward, affects reward value, five pigeons were exposed to a self-control task. They chose between two alternatives, 2s of access to food after a delay of 10s, and 6s of access to food after an adjusting delay. The adjusting delay increased or decreased depending on the pigeons' choices. The delay at which the two alternatives were equally chosen defined the indifference point. To determine whether requiring responses during the delay led to more impulsive (smaller-sooner rewards) or self-controlled (larger-later rewards) choices, we varied the number of required pecks during the 10-s delay to the 2-s reinforcer, and assessed how the requirement affected the indifference points. In the High Rate Phase, they had to peck at least 10 times during the delay; in the Low Rate Phase, they could peck at most 5 times during the delay. For four pigeons the indifference point increased with the response requirement; for one pigeon it decreased. The results suggest that, in general, reward value varies inversely with effort., This work was supported by the Portuguese Foundation for Science and Technology (FCT) Grant (PTDC/MHC-PCN/3540/2012) to Armando Machado and Marco Vasconcelos. 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 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

To contrast the classic version of the Scalar Expectancy Theory (SET) with the Behavioral Economic Model (BEM), we examined the effects of trial frequency on human temporal judgments. Mathematical analysis showed that, in a temporal bisection task, SET predicts that participants should show almost exclusive preference for the response associated with the most frequent duration, whereas BEM predicts that, even though participants will be biased, they will still display temporal control. Participants learned to emit one response (R[S]) after a 1.0-s stimulus and another (R[L]) after a 1.5-s stimulus. Then the effects of varying the frequencies of the 1.0-s and 1.5-s stimuli were assessed. Results were more consistent with BEM than with SET. Overall, this research illustrates how the impact of non-temporal factors on temporal discrimination may help us to contrast associative models such as BEM with cognitive models such as SET. Deciding between these two classes of models has important implications regarding the relations between associative learning and timing. This article is part of a Special Issue entitled: Associative and Temporal Learning., This research was supported by NIH grant MH033881. Jeremie Jozefowiez and Armando Machado acknowledge support from the Fundacao para a Ciencia e a Tecnologia as well as from the European project COST ISCH Action TD0904 "Time in Mental activity" (www.timely-cost.eu). We would like to thank Sean Gannon and Sarah Sterling for help running parts of the experiments, Mario Laborda, Bridget McConnell, Gonzalo Miguez, and James Witnauer for comments on an earlier version of this manuscript. Correspondence concerning this article should be addressed to Jeremie Jozefowiez, laboratoire URECA, Universite Lille Nord de France, Campus de Lille3, Domaine Universitaire du Pont de Bois, BP 60149, 58653 Villeneuve d'Ascq Cedex, France. jeremie.jozefowiez@univ-lille3fr.

This study examined how two models of timing, scalar expectancy theory (SET) and learning to time (LeT), conceptualize the learning process in temporal tasks, and then reports two experiments to test these conceptualizations. Pigeons responded on a two-alternative free-operant psychophysical procedure in which responses on the left key were reinforceable during the first two, but not the last two, quarters of a 60-s trial, and responses on the right key were reinforceable during the last two, but not the first two, quarters of the trial. In Experiment 1 three groups of birds experienced a difference in reinforcement rates between the two keys only at the end segments of the trial (i.e., between the first and fourth quarters), only around the middle segments of the trial (i.e., between the second and third quarters), or in both end and middle segments. In Condition 1 the difference in reinforcement rate favored the left key; in Condition 2 it favored the right key. When the reinforcement rates differed in the end segments of the trial, the psychometric function--the proportion of right responses across the trial--did not shift across conditions; when it occurred around the middle of the trial or in both end and middle segments, the psychometric function shifted across conditions. Experiment 2 showed that the psychometric function shifts even when the overall reinforcement rate for the two keys is equal, provided the rates differ around the middle of the trial. This pattern of shifts of the psychometric function is inconsistent with SET. In contrast, LeT provided a good quantitative fit to the data.

This study examined how pigeons discriminate the relative frequencies of events when the events occur serially. In a discrete-trials procedure, 6 pigeons were shown one light nf times and then another nl times. Next, they received food for choosing the light that had occurred the least number of times during the sample. At issue were (a) how the discrimination was related to two variables, the difference between the frequencies of the two lights, D = nf - nl, and the total number of lights in the sample, T = nf + nl; and (b) whether a simple mathematical model of the discrimination process could account for the data. In contrast with models that assume that pigeons count the stimulus lights, engage in mental arithmetic on numerons, or remember the number of stimuli, the present model assumed only that the influence of a sample stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent. The results showed that, overall, the pigeons discriminated the relative frequencies well. Their accuracy always increased with the absolute value of the difference D and, for D > 0, it decreased with T. Performance also showed clear recency, primacy, and contextual effects. The model accounted well for the major trends in the data.

Two theories of timing, scalar expectancy theory (SET) and learning to time (LeT), make substantially different assumptions about what animals learn in temporal tasks. In a test of these assumptions, pigeons learned two discriminations: On Type 1 trials, they learned to choose a red key after a 1-s signal and a green key after a 4-s signal; on Type 2 trials, they learned to choose a blue key after a 4-s signal and a yellow key after a 16-s signal. Then, two psychometric functions were obtained by presenting them with intermediate durations (1 to 4 s and 4 to 16 s). The two functions did not superpose, and most bisection points were not at the geometric mean of the training stimuli (contra SET); for most birds, the function for Type 2 trials was to the left of the function for Type 1 trials (contra LeT). Finally, the birds were exposed to signals ranging from 1 to 16 s and given a choice between novel key combinations (e.g., red vs. blue). The results with the novel key combinations were always closer to LeT's than to SET's predictions. Observations of the birds' behavior also suggest that, more than being a mere expression of an internal clock, behavior constitutes the clock.

This study reexamined the processes of acquisition and extinction under periodic reinforcement. During the first phase of the experiment, pigeons were exposed to a fixed-interval schedule either 40 or 80 s long. During the second phase, each session started with the fixed-interval schedule but changed to extinction at an unpredictable moment. The results showed that during phase 1 the curve for the average rate of pecking along the interval rotated across sessions, that is, the rate immediately after food decreased, whereas the rate at the end of the interval increased. The initial and terminal rates approached their steady state at different speeds. During the extinction trials of phase 2, behavior was characterized by pause-peck oscillations with a period slightly longer than the fixed-interval duration. These findings concerning acquisition and extinction under periodic reinforcement were then compared with the predictions of some current theories of timing.

The authors argue that some of C R. Gallistel's (2007) and H. C Lau's (2007) solutions to the problems raised in the article by A. Machado and F. J. Silva (2007) are unlikely, logically inconsistent, or at odds with empirical evidence. In particular, Lau seems not to appreciate the necessity of clear and consistent psychological constructs before trying to map these constructs to brain structure and function. The authors conclude that conceptual analysis is a much-needed component of the scientific method., info:eu-repo/semantics/publishedVersion

Overshadowed by more popular disciplines, the study of learning seems to have lost its prominent place in the undergraduate psychology curriculum. In the first part of this essay, we argue that one reason for this state of affairs is the current content of psychology of learning courses, namely, its disproportionate emphasis on facts, procedures, and everyday examples at the expense of functional and conceptual investigations. In the second part of the essay, we outline an alternative approach to the teaching of learning, one that emphasizes basic contents such as the conceptualization of learning as a biological adaptation or the study of temporal regulation, critical methodological issues such as the logic of experimental designs or the difficulties of measuring behavior, and broad epistemological problems such as the role of hypothetical constructs, the advantages of quantitative reasoning, or the origins of knowledge and its integration. By using learning as a means towards more fundamental ends, the splendor of the discipline and its prominent place in the undergraduate curriculum may be restored.

Three experiments compared the amounts of behavioral variability generated with two reinforcement rules. In Experiments 1 and 2 pigeons received food whenever they generated a sequence of eight pecks, distributed over two keys, provided that the sequence contained a certain number of change-overs between the keys. Although no variability was required-the birds could obtain all reinforcers by repeating the same sequence-the pigeons emitted a large number of different sequences. In Experiment 3 pigeons received food whenever they generated a sequence that had not occurred during the last 25 trials. After prolonged training, the birds showed more sequence variability than in the first two experiments. The analysis of the internal structure of the response sequences revealed that, in general, (a) the location of the first peck was highly stereotyped; (b) as the trial advanced, the probability of switching to the initially preferred key decreased whereas the probability of switching to the other key increased; and (c) a first-order Markov chain model with transition probabilities given by a logistic function accounted well for the internal structure of the birds' response sequences. These findings suggest that, to a large extent, the variability of response sequences is an indirect effect of adjustments in changeover frequency.

This study presents a dynamic model of how animals learn to regulate their behavior under time-based reinforcement schedules. The model assumes a serial activation of behavioral states during the interreinforcement interval, an associative process linking the states with the operant response, and a rule mapping the activation of the states and their associative strength onto response rate or probability. The model fits data sets from fixed-interval schedules, the peak procedure, mixed fixed-interval schedules, and the bisection of temporal intervals. The major difficulties of the model came from experiments that suggest that under some conditions animals may time 2 intervals independently and simultaneously.

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.

Models of timing differ on two fundamental issues, the form of the representation and the content of learning. First, regarding the representation of time some models assume a linear encoding, others a logarithmic encoding. Second, regarding the content of learning cognitive models assume that the animal learns explicit representations of the intervals relevant to the task and that their behavior is based on a comparison of those representations, whereas associative models assume that the animal learns associations between its representations of time and responding, which then drive performance. In this paper, we show that some key empirical findings (timescale invariant psychometric curves, bisection point at the geometric mean of the trained durations in the bisection procedure, and location of the indifference point in the time-left procedure) seem to make these two issues interdependent. That is, cognitive models seem to entail a linear representation of time, and at least a certain class of associative models seem to entail a log representation of time. These interdependencies suggest new ways to compare and contrast timing models., Jeremie Jozefowiez and Armando Machado acknowledge support from the Fundacao para a Ciencia e a Tecnologia as well as from the European project COST ISCH Action TD0904 "Time in Mental activity" (www.timely-cost.eu)., info:eu-repo/semantics/publishedVersion

In two experiments, we investigated emergent conditional relations in pigeons using a symbolic matching-to-sample task with temporal stimuli as the samples and hues as the comparisons. Both experiments comprised three phases. In Phase I, pigeons learned to choose a red keylight (R) but not a green keylight (G) after a 1-s signal. They also learned to choose G but not R after a 4-s signal. In Phase II, correct responding consisted of choosing a blue keylight (B) after a 4-s signal and a yellow keylight (Y) after a 16-s signal. Comparisons G and B were both related to the same 4-s sample, whereas comparisons R and Y had no common sample. In Phase III, R and G were presented as samples, and B and Y were presented as the comparisons. The choice of B was correct following G, and the choice of Y was correct following R. If a relation between comparisons that shared a common sample were to emerge, then responding to B given G would be more likely than responding to Y given R. The results were generally consistent with this prediction, suggesting, for the first time in pigeons, the emergence of novel relations that involve temporal stimuli as nodal samples., This research was supported by doctoral grants to E.M.H. (FAPESP 60678-4/05 and CAPES 0103/08 0) and S.M.V. (CNPq 142544/2005-1 and CAPES 4457 07 2). G.Y.T. and D.G.d.S. were supported by a research productivity fellowship from The National Council for Scientific and Technological Development (CNPq, Brazil). A.D.M. was funded by the Portuguese Foundation for Science and Technology (FCT). All of the Brazilian authors are currently affiliated with the National Institute of Science and Technology on Behavior, Cognition and Teaching, supported by FAPESP (Grant No. 08/57705-8) and CNPq (Grant No. 573972/2008-7). The data were collected in the Animal Learning and Behavior Laboratory, University of Minho, Portugal, and were presented at the 36th Annual Meeting of the Brazilian Society of Psychology (SBP), Goiania, Brazil, in October 2009. E.M.H. is currently a college professor at the Universidade Federal de Minas Gerais., info:eu-repo/semantics/publishedVersion

The experiment examined how pigeons differentiate response patterns along the dimension of number. Seven pigeons received food after pecking the left key at least N times and then switching to the right key (Mechner’s Fixed Consecutive Number schedule). Parameter N was set according to a percentile schedule, which is a form of automatic shaping. Our aim was twofold: on the empirical side to determine how run length on the left key would evolve under this shaping procedure and how it would change during a subsequent extinction phase; and on the theoretical side to compare the data with the predictions of a theoretical model of response differentiation. Results showed that during shaping, run length on the left key increased and then, for some pigeons, it stabilized, whereas for others pigeons it remained variable. Some pigeons ceased to respond when average run length reached a highvalue. There were substantial within-session trends in run length. In extinction, before the pigeons ceased to respond altogether, they emitted the same distribution of run lengths as during the last sessions of shaping with the exception, in some birds, of a large number of runs of length zero. These results are interpreted at the light of the theoretical model of numerosity differentiation.Keywords: Mathematical Model, Response Numerosity, Percentile Schedule, Shaping, Pigeon, O presente estudo analisa a diferenciação numérica de padrões de resposta. Em uma caixa de Skinner com duas teclas, sete pombos receberam comida após bicarem pelo menos N vezes na tecla esquerda e depois uma vez na tecla direita (programa “Fixed Consecutive Number” de Mechner). Em cada ensaio, o parâmetro N era ajustado por um programa de reforço percentil (uma forma de shaping automático). O estudo teve dois objetivos. Primeiro, determinar como é que varia o tamanho das corridas na tecla da esquerda durante o procedimento de modelagem (shaping) e durante uma fase de extinção que se seguiu. Segundo, comparar os dados obtidos com as previsões de um modelo teórico de diferenciação da resposta. Os resultados mostraram que, durante a modelagem, o tamanho das corridas na tecla esquerda aumentou e depois, para alguns pombos, estabilizou, enquanto para outros pombos permaneceu variável. Alguns pombos pararam de responder quando o tamanho médio da corrida atingiu valores elevados. Observaram-se ainda variações sistemáticas nos tamanhos das corridas no interior de cada sessão como, por exemplo, o aumento do tamanho da corrida ao longo da sessão. Durante a fase de extinção os pombos produziram distribuições de tamanhos de corrida semelhantes às distribuições produzidas durante as últimas sessões de modelagem com exceção, em alguns sujeitos, do elevado número de corridas de tamanho zero. Estes resultados são interpretados à luz do modelo teórico de diferenciação numérica das respostas. Palavras-chave: Modelo matemático, numerosidade, esquema percentil, modelagem, pombo

In a temporal double bisection task, animals learn two discriminations. In the presence of Red and Green keys, responses to Red are reinforced after 1-s samples and responses to Green are reinforced after 4-s samples; in the presence of Blue and Yellow keys, responses to Blue are reinforced after 4-s samples and responses to Yellow are reinforced after 16-s samples. Subsequently, given a choice between Green and Blue, the probability of choosing Green increases with the sample duration_the context effect. In the present study we asked whether this effect could be predicted from the stimulus generalization gradients induced by the two basic discriminations. Six pigeons learned to peck Green following 4-s samples (S+) but not following 1-s samples (S2) and to peck Red following 4-s samples (S+) but not following 16-s samples (S2). Temporal generalization gradients for Green and Red were then obtained. Finally, the pigeons were given a choice between Green and Red following sample durations ranging from 1 to 16 s. Results showed that a) the two generalization gradients had the minimum at the S2 duration, an intermediate value between the S2 and the S+ durations, and the maximum at the S+ as well as more extreme durations; b) on choice trials, preference for Green over Red increased with sample duration, the context effect; and c) the two generalization gradients predicted the average context effect well. The Learning-to-Time model accounts for the major trends in the data., The authors 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).

In a discrete-trials procedure, a frequency-dependent schedule shaped left-right choice proportion toward various equilibrium values between 0 and 1. At issue was (1) whether pigeons match when the overall reinforcement probabilities for two responses depend inversely on their recent frequency, and (2) how pigeons meet the schedule constraint in terms of local responding. That is, do they respond quasi-randomly (Bernoulli mode), or do they learn the stable pattern of the schedule (stable-pattern mode)? Molar choice behavior always tracked the equilibrium solution of the schedule, but the molecular response patterns varied substantially. Markov chains applied to the data revealed that responding was generally intermediate between the memoryless Bernoulli mode, and the perfect memory stable-pattern mode. The polymorphism of molecular patterns, despite molar regularities in behavior, suggests that (1) in order to engender the Bernoulli or stable-pattern modes, the reinforcement rule must strongly discourage competing response patterns (e.g., perseveration), and (2) under frequency-dependent schedules, molar matching is apparently not the outcome of momentary maximizing.

When subjects learn to associate two sample durations with two comparison keys, do they learn to associate the keys with the short and long samples (relational hypothesis), or with the specific sample durations (absolute hypothesis)? We exposed 16 pigeons to an ABA design in which phases A and B corresponded to tasks using samples of 1s and 4 s, or 4 s and 16 s. Across phases, we varied the mapping between the samples and the keys. For group Relative, short and long samples were always associated with the same keys (e.g., Phase A: ‘1s--> Left, 4 s--> Right’; Phase B: ‘4 s--> Left, 16 s--> Right’); for group Absolute, the 4-s sample was associated always with the same key (e.g., Phase A: ‘1s--> Left, 4 s--> Right’; Phase B: ’16 s--> Left, 4 s--> Right”). If temporal control is relational, group Relative should learn the new task faster than group Absolute, but if temporal control is absolute, the opposite should occur. We compared the results with the predictions of the Learning-to-Time (LeT) model, which accounts for temporal discrimination in terms of absolute stimulus control and stimulus generalization. The acquisition curves of the two groups were generally consistent with LeT and therefore more consistent with the absolute than the relative hypothesis., The authors thank the members of the Animal Learning and Behavior Lab of the University of Minho for their helpful comments. The work was supported by grants to the two authors from the Portuguese Foundation for Science and Technology (FCT).

In the present study we extended errorless learning to a conditional temporal discrimination. Pigeons’ responses to a left–red key after a 2-s sample and to a right–green key after a 10-s sample were reinforced. There were two groups: One learned the discrimination through trial and error and the other through an errorless learning procedure. Then, both groups were presented with three types of tests. First, they were exposed to intermediate durations between 2 s and 10 s, and given a choice between both keys (stimulus generalization test). Second, a delay from 1 s to 16 s was included between the offset of the sample and the onset of the choice keys (delay test). Finally, pigeons learned a new discrimination in which the stimuli were switched (reversal test). Results showed that pigeons from the Errorless group made significantly fewer errors than those in the Trial-and-Error group. Both groups performed similarly during the stimulus generalization test and the reversal test, but results of the delay test suggested that, on long stimulus trials, responding in the errorless training group was less disrupted by delays., This research was presented in part at the 33rd Annual Convention of the Association of Behavioral Analysis (ABA) in San Diego, California. The authors were supported by the Portuguese Foundation for Science and Technology (FT). The authors thank Herbert S. Terrace for his valuable thoughts at the 31st Annual Meeting of the Society for the Quantitative Analyses of Behavior (SQAB) about this research.

The “A-not-B” error is consistent with an old memory principle, Jost's Law. Quantitative properties of the effect can be explained by a dynamic model for habituation that is also consistent with Jost. Piaget was well aware of the resemblance between adult memory errors and the “A-not-B” effect and, contrary to their assertions, Thelen et al.'s analysis of the object concept is much the same as his, though couched in different language.

The present experiment investigated whether pigeons can show associative symmetry on a two-alternative matching to-sample procedure The procedure consisted of a within subject sequence of training and testing with reinforcement and It provided (a) exemplars of symmetrical responding and (b) all prerequisite discriminations among test samples and comparisons After pigeons had learned two arbitrary matching tasks (A B and C D) they were given a reinforced symmetry test for half of the baseline relations (B1-A1 and D1-C1) To control for the effects of reinforcement during testing two novel nonsymmetrical responses were concurrently reinforced using the other baseline stimuli (D2-A2 and B2-C2) Pigeons matched at chance on both types of relations thus indicating no evidence for symmetry These symmetrical and nonsymmetrical relations were then directly trained in order to provide exemplars of symmetry and all prerequisite discriminations for a second test The symmetrical test relations were now B2-A2 and D2-C2 and the nonsymmetrical relations were D1-A1 and B1-C1 On this test 1 pigeon showed clear evidence of symmetry 2 pigeons showed weak evidence and 1 pigeon showed no evidence The previous training of all prerequisite discriminations among stimuli and the within subject control for testing with reinforcement seem to have set favorable conditions for the emergence of symmetry in nonhumans However the variability across subjects shows that methodological variables still remain to be controlled, This research was supported by Doctoral Grant (CNPq 142544/2005-1) and Doctoral Sandwich Grant (CAPES 4457-07 2) to Saulo M Velasco Doctoral Grant (FAPESP 60678-4/05) and Doctoral Sandwich Grant (CAPES 0103/08-0) to Edson M Huziwara Researcher Grant (CNPq 302640/2007-0) and Research Support (CNPq 471953/2004-0) to Gerson Y Tomanari Armando Machado was funded by the Portuguese Foundation for Science and Technology (FCT), info:eu-repo/semantics/publishedVersion

In the time-left procedure, a task used to study prospective timing, animals choose between two stimuli that signal different delays to reinforcement. Trials begin with one stimulus signaling C seconds to reinforcement and, at different moments since its onset, another stimulus, signaling S seconds to reinforcement, with C>S, is introduced. Optimal performance consists in choosing the stimulus signaling the shorter time to reinforcement. Animals have been found to perform in this optimal way. However, this procedure is complex and variables other than time may be responsible for the results. In two experiments with pigeons we sought to improve the time-left procedure to better isolate the effect of time in the animals' behavior. We attempted to control for two confounding variables, the asymmetry in the time markers from training to testing and the cost of switching between the two response alternatives. We conclude that in the time-left task pigeons seem indeed to regulate their behavior based on time because, with our improved procedure, they still chose the stimulus associated with the shorter time to food. However, our version of the procedure created new interpretative difficulties, strengthening the idea that the time-left procedure may be too complex to study timing., The authors would like to thank Luis Oliveira for his help in developing the present study and Jeremie Jozefowiez for comments on an earlier version of the manuscript. Work supported by the Portuguese Foundation for Science and Technology (FCT) grants SFRH/BD/43398/2008 and PTDC/PSI/65678/2006., info:eu-repo/semantics/publishedVersion

O objetivo deste modelo é apresentar um planejamento financeiro de execução de obras da construção civil, usando apenas recursos próprios, sem comprometer o prazo de entrega, nem a imagem da construtora, com otimização utilizando o simplex. Um melhor resultado para a filial de Recife é perseguido exaustivamente. A realidade do mercado imobiliário da cidade de Recife e as práticas existentes num grupo construtor são descritas e servem de pano para a problemática do planejamento e a solução adotada, a partir da sustentação teórica. Os resultados alcançados são analisados de forma aberta. As novas realidades, oriundas da implantação do planejamento, bem como os melhoramentos no modelo que se fizeram necessários são apresentados e analisados, na sua ordem cronológica. Além de tudo, é um registro interessante de como uma empresa preocupada na melhoria de sua gestão, aprende com seus erros e se adapta a novas realidades, sem perder seu foco

In the last decades, researchers have proposed a large number of theoretical models of timing. These models make different assumptions concerning how animals learn to time events and how such learning is represented in memory. However, few studies have examined these different assumptions either empirically or conceptually. For knowledge to accumulate, variation in theoretical models must be accompanied by selection of models and model ideas. To that end, we review two timing models, Scalar Expectancy Theory (SET), the dominant model in the Field, and the Learning-to-Time (LeT) model, one of the few models dealing explicitly with learning. In the first part of this article, we describe how each model works in prototypical concurrent and retrospective timing tasks, identify their structural similarities, and classify their differences concerning temporal learning and memory. In the Second part, we review a series of studies that examined these differences and conclude that both the memory structure postulated by SET and the state dynamics postulated by LeT are probably incorrect. In the third part, we propose a hybrid model that may improve on its parents. The hybrid model accounts for the typical findings in fixed-interval schedules, the peak procedure, mixed fixed interval schedules, simple and double temporal bisection, and temporal generalization tasks. In the fourth and last part, we identify seven challenges that any timing model trust meet., Fundação para a Ciência e a Tecnologia (FCT)

We examined if the representation of time intervals in a temporal discrimination task is based not only on their absolute but also on their relative durations. Six pigeons learned two temporal discriminations. In the first, red and green choices were correct following 2-s and 8-s samples, respectively. In the second, vertical and horizontal bar choices were correct following 4-s and 16-s samples, respectively. In a previous study [Zentall, T.R., Weaver, J.E., Clement, T.S., 2004. Pigeons group time intervals according to their relative duration. Psychon. Bull. Rev. 11, 113-117.]. tests with 4-s samples and red/green comparisons revealed a bias for red, whereas tests with 8-s samples with vertical/horizontal comparisons revealed a bias for horizontal. These results were interpreted in terms of relative encoding of sample durations. We attempted to replicate this finding but instead of testing with only 4-s or 8-s samples, we tested with several other sample durations to obtain a psychometric function. Results were inconsistent with the relative encoding hypothesis., Part of the work reported here was included in a Masters thesis submitted by the first author to the University of Minho, Portugal. Research supported by a grant from the Portuguese Foundation for Science and Technology (FCT) to the second author., info:eu-repo/semantics/publishedVersion

Three experiments examined behavior in extinction following periodic reinforcement. During the first phase of Experiment 1, four groups of pigeons were exposed to fixed interval (FI 16s or FI 48s) or variable interval (VI 16 s or VI 48 s) reinforcement schedules. Next, during the second phase, each session started with reinforcement trials and ended with an extinction segment. Experiment 2 was similar except that the extinction segment was considerably longer. Experiment 3 replaced the FI schedules with a peak procedure, with FI trials interspersed with non-food peak interval (PI) trials that were four times longer. One group of pigeons was exposed to A 20 s PI 80 s trials, and another to FI 40 s PI 160 s trials. Results showed that, during the extinction segment, most pigeons trained with FI schedules, but not with VI schedules, displayed pause-peck oscillations with a period close to, but slightly greater than the Fl parameter. These oscillations did not start immediately after the onset of extinction. Comparing the oscillations from Experiments I and 2 suggested that the alternation of reconditioning and re-extinction increases the reliability and earlier onset of the oscillations. In Experiment 3 the pigeons exhibited well-defined pause-peck cycles since the onset of extinction. These cycles had periods close to twice the value of the FI and lasted for long intervals of time. We discuss some hypotheses concerning the processes underlying behavioral oscillations following periodic reinforcement., Part of the work reported here was included in a Masters thesis submitted by the first author to the University of Minho, Portugal. The work was funded by a grant from the Portuguese Foundation for Science and Technology to the second author. The authors thank Maria José Souza for her help collecting and analyzing the data., info:eu-repo/semantics/publishedVersion

In a symbolic matching to sample task, six pigeons learned to associate different sample durations with different comparison stimuli. On "Short" trials, choice of Red and Green keylight comparisons were reinforced following 3-s and 9-s samples, respectively; on "Long" trials, Blue and Yellow keylight comparisons were reinforced following 9-s and 27-s samples, respectively. in contrast with previous studies, the comparison keys were available during the samples. After the temporal discriminations were learned, new pairs of comparison keys were presented and the preference for each was assessed during 27-s samples. One pair in particular, Green and Blue, was critical because it tested the predictions of two timing models, Scalar Expectancy Theory (SET) and the Learning-to-Time (LeT) model. The results showed that preference for Green increased during the sample, a result consistent with LeT but not with SET. Other test results, however, were predicted by neither model., Research supported by a grant from the Portugese Foundation for Science and Technology (FCT) to the second author., info:eu-repo/semantics/publishedVersion

To test the assumptions of two models of timing, Scalar Expectancy Theory (SET) and Learning to Time (LeT), nine pigeons were exposed to two temporal discriminations, each signaled by a different cue. On half of the trials, pigeons learned to choose a red key after a 1.5-s horizontal bar and a green key after a 6-s horizontal bar; on the other half of the trials, they learned to choose a blue key after a 6-s vertical bar and a yellow key after a 24-s vertical bar. During subsequent test trials, they were exposed to the horizontal or vertical bar, for durations ranging from 1.5 to 24 s, and given a choice between novel key combinations: red vs. yellow, or green vs. blue. Results showed a strong effect of sample duration-as the test signal duration increased, preference for green over blue increased and preference for red over yellow decreased. The effect of sample cue was obtained only on the green-blue test trials. These effects are discussed in light of SET and LeT., The authors thank Francisco Silva for helpful comments. Research supported by a grant from the Portuguese Foundation for Science and Technology (FCT) to the second author., info:eu-repo/semantics/publishedVersion

We used a numerical bisection procedure to examine preschool children's sensitivity to the numerical attributes of stimuli. In Experiment I children performed two tasks. In the Cups Task they earned coins for choosing a green cup after two drumbeats and a blue cup after eight drumbeats. In the Gloves Task they earned coins for raising a red glove on their left hand after two drumbeats and a yellow glove on their right hand after eight drumbeats. Then in each task a psychometric function was obtained by presenting intermediate numerosities and recording the percentage of trials in which children chose the "many" option. In Experiment 2 children's performance in a '2 vs. 8' discrimination was compared with their performance in a "4 vs. 16" discrimination. Results showed that the individual psychometric functions were of two types, one in which the percentage of "many" choices increased gradually with stimulus numerosity and another in which it increased abruptly, in a step-like manner. Although the average point of subjective equality was close to the geometric mean of the anchor numerosities and the average functions for "2 vs. 8" and "4 vs. 16" superimposed when plotted on a common scale (the scalar property), the individual data were highly variable both across tasks (Cups and Gloves) and numerosity ranges (`2 vs. 8' and `4 vs. 16'). It is suggested that between-and within-subjects variability in the psychometric function is related to children's verbalizations about the sample stimulus., info:eu-repo/semantics/publishedVersion

Two experiments examined how pigeons differentiate response patterns along the dimension of number. In Experiment 1, 5 pigeons received food after pecking the left key at least N times and then switching to the right key (Mechner's Fixed Consecutive Number schedule). Parameter N varied across conditions from 4 to 32. Results showed that run length on the left key followed a normal distribution whose mean and standard deviation increased linearly with N; the coefficient of variation approached a constant value (the scalar property). In Experiment 2, 4 pigeons received food with probability p for pecking the left key exactly four times and then switching. If that did not happen, the pigeons still could receive food by returning to the left key and pecking it for a total of at least 16 times and then switching. Parameter p varied across conditions from 1.0 to .25. Results showed that when p= 1.0 or p=.5, pigeons learned two response numerosities within the same condition. When p=.25, each pigeon adapted to the schedule differently. Two of them emitted first runs well described by a mixture of two normal distributions, one with mean close to 4 and the other with mean close to 16 pecks. A mathematical model for the differentiation of response numerosity in Fixed Consecutive Number schedules is proposed., We thank Francisco Silva and Luı´s Oliveira for their comments. Research was supported by a grant from the Portuguese Foundation for Science and Technology (FCT;Pocti/Psi/44136/2002) to the first author., info:eu-repo/semantics/publishedVersion

Within the complex set of activities that comprise the scientific method, three clusters of activities can be recognized: experimentation, mathematization, and conceptual analysis. In psychology, the first two of these clusters are well-known and valued, but the third seems less known and valued. The authors show the value of these three clusters of scientific method activities in the works of the quintessential scientist Galileo Galilei. They then illustrate how conceptual analysis can be used in psychology to clarify the grammar and meaning of concepts, expose conceptual problems in models, reveal unacknowledged assumptions and steps in arguments, and evaluate the consistency of theoretical accounts. The article concludes with a discussion of three criticisms of conceptual analysis., Armando Machado was funded by a grant from the Portuguese Foundation for Science and Technology. We thank Susan Goldstein for sharing her expertise about construct validity, info:eu-repo/semantics/publishedVersion

To contrast two models of timing, Scalar Expectancy Theory (SET) and Learning to Time (LeT), pigeons were exposed to a double temporal bisection procedure. On half of the trials, they learned to choose a red key after a 1 s signal and a green key after a 4 s signal; on the other half of the trials, they learned to choose a blue key after a 4-s signal and a yellow key after a 16-s signal. This was Phase A of an ABA design. On Phase B, the pigeons were divided into two groups and exposed to a new bisection task in which the signals ranged from 1 to 16 s and the choice keys were blue and green. One group was reinforced for choosing blue after 1-s signals and green after 16-s signals and the other group was reinforced for the opposite mapping (green after 1-s signals and blue after 16-s signals). Whereas SET predicted no differences between the groups, LeT predicted that the former group would learn the new discrimination faster than the latter group. The results were consistent with LeT. Finally, the pigeons returned to Phase A. Only LeT made specific predictions regarding the reacquisition of the four temporal discriminations. These predictions were only partly consistent with the results.

According to Grau and Joynes (2005), (1) the current classification of types of learning is based on methodology and assumes a correspondence between types of learning and distinct neural-functional mechanisms; (2) this assumption is wrong because experiments show that different mechanisms may underlie the same type of learning; consequently, (3) we should change the teaching of the psychology of learning. I argue that because Grau and Joynes misunderstood the nature of the classification of learning phenomena and cloaked their research findings with a garb of conceptual errors and infelicities, their recommendations concerning the teaching of learning should be rejected.

To test some predictions of scalar expectancy theory (SET) for the time-left procedure, we performed one experiment with two conditions. In Condition A, pigeons were exposed to two fixed-interval schedules, a fixed-interval (FI) 30s and an FI 60s, each associated with a distinct key and presented on a separate trial. Subsequently, during test trials, the FI 60-s key was illuminated and then after T = 15, 30 or 45 s the FI 30-s key also was illuminated. The main issue was how choice between the two keys varied with T. Condition B replicated Condition A with different FI parameters and T values. The results showed that (a) contrary to SET's predictions, preference changed reliably with testing, which suggests that learning took place during the test trials; (b) within each test trial, pigeons revealed an almost exclusive preference for one of the keys, and (c) at steady state pigeons behaved in the same way as rats. Because SET could not account for these findings we advanced a new descriptive model of performance for the time-left task. The model fit the data well.

Two theories of timing, scalar expectancy theory (SET) and learning-to-time (LeT), make substantially different assumptions about what animals learn in temporal tasks. In a test of these assumptions, pigeons learned two temporal discriminations. On Type 1 trials, they learned to choose a red key after a 1-sec signal and a green key after a 4-sec signal; on Type 2 trials, they learned to choose a blue key after a 4-sec signal and a yellow key after either an 8-sec signal (Group 8) or a 16-sec signal (Group 16). Then, the birds were exposed to signals 1 sec, 4 sec, and 16 sec in length and given a choice between novel key combinations (red or green vs. blue or yellow). The choice between the green key and the blue key was of particular significance because both keys were associated with the same 4-sec signal. Whereas SET predicted no effect of the test signal duration on choice, LeT predicted that preference for green would increase monotonically with the length of the signal but would do so faster for Group 8 than for Group 16. The results were consistent with LeT, but not with SET.

A fim de caracterizar o que se publica em Portugal nas revistas especializadas em psicologia, analisámos os artigos publicados desde 1996 até 2003 em três revistas: Psicologia: teoria, investigação e prática, associada à Universidade do Minho; Psychologica, associada à Universidade de Coimbra; e Análise Psicológica, associada ao Instituto Superior de Psicologia Aplicada, Lisboa. Após descrevermos a nacionalidade, género e filiação institucional dos autores dos artigos, classificámos o conteúdo de cada artigo em termos de área temática e de metodologia utilizada. Os resultados – muito semelhantes nas três revistas – mostram que a) os artigos provêm sobretudo de autores portugueses com filiação universitária, muitas vezes na própria instituição que publica a revista; b) os artigos versam sobretudo os domínios aplicados da clínica e da educação; c) cerca de metade dos artigos consiste em revisões de literatura ou análises conceptuais; e d) apenas cinco por cento utiliza metodologia experimental. Estes resultados são interpretados à luz do contexto universitário português, em geral, e da nossa experiência de investigação em Portugal, em particular. To characterize what gets published in specialized Portuguese journals of psychology, we analyzed the articles published from 1996 to 2003 in three journals: Psicologia: teoria, investigação e prática, associated with the University of Minho; Psychologica, associated with the University of Coimbra; and Análise Psicológica, associated with the Instituto Superior de Psicologia Aplicada, located at Lisbon. We tabulated the nationality, gender, and institutional affiliation of the authors of the articles and also classified the articles in terms of their content area and methodology. The results, which were similar across the three journals, showed that a) most of the authors are Portuguese working at a university, often at the same university that publishes the journal; b) the articles address mainly the applied areas of clinical and educational psychology; c) half of the articles consist of literature reviews or conceptual analyses; and d) only five per cent used experimental methodology. The results are interpreted at the light of the Portuguese university context, in general, and our research experiences in Portugal, in particular. info:eu-repo/semantics/publishedVersion

Pigeons were placed in a long chamber equipped with one key and feeder at each end side and one key and houselight at the middle. To obtain food the birds had to choose one side key after a short signal and the other side key after a long signal. The signals consisted of the illumination of the center key and the houselight and were initiated by a peck at the center key. The chamber had sensitive floor panels that enabled us to measure the location of the bird during the signals. In Experiment 1, after the birds learned the discrimination we reversed the assignment of keys to signals. In Experiment 2, we examined performance on two pairs of discriminations holding the same ratio. In Experiment 3, after the pigeons learned to discriminate two signals, we changed the duration of the long signal. The results showed that (a) the birds' motion during the signal was highly stereotypical, i.e. the birds moved to the short side, waited a few seconds, and then departed to, and stayed on the long side; (b) this motion pattern predicted the results of generalization tests with novel durations; (c) the mean of the times of departure from the short side approached its steady state values quicker than the standard deviation and consequently superposition of behavioral measures became stronger with training; (d) only the duration of the short signal influenced significantly the moment the birds departed from the short side: finally (e) the times of arrival at and departure from the short side were positively correlated, but the times of arrival and residence at the short side were negatively correlated., info:eu-repo/semantics/publishedVersion

We reviewed Daniel Povinelli's book, Folk physics for apes: The chimpanzee's theory of how the world works. After a summary of the book's contents, we analyzed two sets of experiments on chimpanzees' folk psychology: one that explored whether chimpanzees understand that others see (i.e., that apes have internal visual experiences) and another that examined whether chimpanzees can distinguish intended from unintended actions. The conceptual scaffolding on which these studies were conceived was sufficiently faulty that their outcomes were virtually assured a priori. We then analyzed two sets of experiments on chimpanzees' folk physics, reinforcing our view that conceptual confusion guaranteed that certain key predictions about the outcome of these studies could not be supported. A unifying reason for this conceptual confusion is that the author devalues understanding that results from programmatic conditioning. We closed the review by relating Povinelli's findings and conclusions to behavior analysis and by explaining why behavior analysts should read this book.

This study tested a model of how animals discriminate the relative numerosity of stimuli in successive or sequential presentation tasks. In a discrete-trials procedure, pigeons were shown one light for nf times and then another for nl times. Next they received food for choosing the light that had occurred the least-number of times during the sample. At issue were (a) how performance varies with the interval between the two stimulus sets (the interblock interval) and the interval between the end of the sample and the beginning of the choice period (the retention interval); and (b) whether a simple mathematical model of the discrimination process could account for the data. The model assumed that the influence of a stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent; choice probability is given by the ratio of the influence values of the two stimuli. The model also assumed that as the retention interval elapses there is an increasing probability that the ongoing discriminative process be disrupted and then the animal responds randomly. Results showed that increasing the interblock intervals reduced the probability of choosing the last stimulus of the sample as the least-frequent one. Increasing the retention interval reduced accuracy without inducing any stimulus bias. The model accounted well for the major trends in the data.

Five experiments addressed the issue of how pigeons learn to discriminate the relative frequency of stimuli. During a sampling period, three different stimuli (keylights) were presented serially, in mixed order, and with different frequencies. During a choice period, the stimuli were presented simultaneously, and reinforcement was arranged for choosing the stimulus that was presented the least number of times during the sample. The results showed that (a) the overall proportion of correct choices was always above chance levels; (b) the likelihood of a correct choice decreased with the serial position of the correct stimulus, a negative recency effect; (c) when the last three stimuli of the sample were constrained to be one of each kind, the negative recency effect decreased but errors became more likely when the correct stimulus occurred early in the sample, a negative primacy effect; (d) accurate performance generalized to new and larger samples; and (e) under some conditions the probability of a correct choice was independent of the serial position of the correct stimulus. The serial position curves suggest that in a least frequent discrimination task, two processes determine how the least frequent stimulus controls behavior: a passive decay process (the stimulus loses its effectiveness with time since its last occurrence), and a residual salience process (when the stimulus occurs in the first position it may decay to a higher asymptote than when it occurs in later positions.

Economia Monetária e Financeira Submitted by Susana Vilar (svilar@iseg.ulisboa.pt) on 2018-05-14T15:42:24Z No. of bitstreams: 1 TD-JAMA-1995.pdf: 38576992 bytes, checksum: fc849a8a2e4662ca6ccdb3e180c981c7 (MD5) Made available in DSpace on 2018-05-14T15:42:24Z (GMT). No. of bitstreams: 1 TD-JAMA-1995.pdf: 38576992 bytes, checksum: fc849a8a2e4662ca6ccdb3e180c981c7 (MD5) Previous issue date: 1995-12 N/A