The Sometimes Context-Specific Habituation: Theoretical Challenges to Associative Accounts.

A substantial corpus of experimental research indicates that in many species, long-term habituation appears to depend on context-stimulus associations. Some authors have recently emphasized that this type of outcome supports Wagner's priming theory, which affirms that responding is diminished when the eliciting stimulus is predicted by the context where the animal encountered that stimulus in the past. Although we agree with both the empirical reality of the phenomenon as well as the principled adequacy of the theory, we think that the available evidence is more provocative than conclusive and that there are a few nontrivial empirical and theoretical issues that need to be worked out by researchers in the future. In this paper, we comment on these issues within the framework of a quantitative version of priming theory, the SOP model.

SOP- habituation laboratory: An interactive tool for simulating the basic behavioral features of habituation.

This paper presents an open-source online tool for introducing psychology students to the major theoretical and empirical facts of habituation. The tool was designed in a way that combines theory and data through simulated experiments. The simulations exemplify how the priming theory of Allan R. Wagner accounts for the set of behavioral characteristics of habituation proposed by Richard F. Thompson and W. Alden Spencer in 1966. Through this interactive platform, the user can learn the basics of the theory and examine how it accounts for the empirical facts with different parameters. Instructions and commands are provided in three languages: English, Spanish, and Portuguese.

A Quantitative Account of the Behavioral Characteristics of Habituation: The Sometimes Opponent Processes Model of Stimulus Processing.

Habituation is defined as a decline in responding to a repeated stimulus. After more than 80 years of research, there is an enduring consensus among researchers on the existence of 9-10 behavioral regularities or parameters of habituation. There is no similar agreement, however, on the best approach to explain these facts. In this paper, we demonstrate that the Sometimes Opponent Processes (SOP) model of stimulus processing accurately describes all of these regularities. This model was proposed by Allan Wagner as a quantitative elaboration of priming theory, which states that the processing of a stimulus, and therefore its capacity to provoke its response, depends inversely on the degree to which the stimulus is pre-represented in short-term memory. Using computer simulations, we show that all the facts involving within-session effects or short-term habituation might be the result of priming from recent presentations of the stimulus (self-generated priming). The characteristics involving between-sessions effects or long-term habituation would result from the retrieval of the representation of the stimulus from memory by the associated context (associatively generated priming).

The development and present status of the SOP model of associative learning.

The Sometimes Opponent Processes (SOP) model in its original form was especially calculated to address how expected unconditioned stimulus (US) and conditioned stimulus (CS) are rendered less effective than their novel counterparts in Pavlovian conditioning. Its several elaborations embracing the essential notion have extended the scope of the model to integrate a much greater number of phenomena of Pavlovian conditioning. Here, we trace the development of the model and add further thoughts about its extension and refinement.

Cue competition effects in human causal learning.

Five experiments involving human causal learning were conducted to compare the cue competition effects known as blocking and unovershadowing, in proactive and retroactive instantiations. Experiment 1 demonstrated reliable proactive blocking and unovershadowing but only retroactive unovershadowing. Experiment 2 replicated the same pattern and showed that the retroactive unovershadowing that was observed was interfered with by a secondary memory task that had no demonstrable effect on either proactive unovershadowing or blocking. Experiments 3a, 3b, and 3c demonstrated that retroactive unovershadowing was accompanied by an inflated memory effect not accompanying proactive unovershadowing. The differential pattern of proactive versus retroactive cue competition effects is discussed in relationship to amenable associative and inferential processing possibilities.

Especificidad contextual diferencial en la habituación de las respuestas de parpadeo y aceleración cardiaca en humanos / Differential Context-Specificity in the Habituation of the Eyeblink and Cardiac Responses in Humans

Wagner (1978) propuso que la habituación, definida como una disminución en la respuesta a un estímulo que se repite, dependería de la formación de una asociación entre el contexto y el estímulo. Según este enfoque, la habituación debería ser contexto-específica, es decir, la respuesta habituada en un contexto debería deshabituarse al presentar el estímulo en un contexto novedoso. Esta hipótesis fue examinada a través de un experimento donde se sometió a un grupo de estudiantes a una sesión de habituación consistente en 60 repeticiones de un estímulo provocador de reacciones de parpadeo y aceleración cardiaca. Posteriormente, en una sesión de prueba se midió la amplitud de estas respuestas, presentando el estímulo en el mismo contexto (Grupo Igual) o en un contexto distinto a aquel donde ocurrió la habituación (Grupo Diferente). Los resultados de la prueba arrojaron evidencia de especificidad contextual diferencial para ambas respuestas, ya que la respuesta de aceleración cardiaca resultó disminuida en el grupo igual pero no en el grupo diferente (revelando especificidad), mientras que la respuesta de parpadeo estuvo igualmente disminuida en ambos grupos (revelando ausencia de especificidad). Estos hallazgos confirman observaciones previas con ratas que demuestran que el control contextual de la habituación depende de la naturaleza de la respuesta.

Wagner (1978) proposed that habituation, defined as a decrease in responding to a repeated stimulus, would depend on the formation of an association between the stimulus and the context. According to this approach, habitua-tion should be context-specific; that is, a response that was habituated in a given context should dishabituate when the stimulus is presented in a novel context. This hypothesis was examined in an experiment in which a group of students received a habituation session consisting of 60 repetitions of a stimulus capable of evoking eyeblink and heart-rate acceleration reactions. Subsequently, in a testing session the amplitude of these responses was examined by presenting the stimulus in the same context used in the habituation session (Group Same) or in an alternative context (Group Different). The results provided evidence of differential context-specificity for the two responses, since the heart-rate acceleration response was diminished in the group same but not in the group different (revealing specificity), while the eyeblink response was diminished in both groups (revealing no specificity). These findings are consistent with previous observations in rats demonstrating that the contextual control of habituation depends on the nature of the measured response.

Reinstatement of short-latency responses after asymptotic Pavlovian conditioning training by the presentation of an extraneous stimulus.

The purpose of this study was to examine whether the progressive disappearance of short-latency conditioned responses, or inhibition of delay, observed in Pavlovian conditioning with long inter-stimulus intervals, could be reverted by the presentation of a novel stimulus. In one experiment, two groups of rabbits received extensive training with a short (250 ms) or a long (1500 ms) tone that overlapped and terminated with a periorbital shock unconditioned stimulus. After training, the presentation of an extraneous stimulus prior to tone onset produced a reinstatement of short latency CRs in the group trained with the long CS, but did not affect CR latency in the group trained with the short CS. This finding is consistent with Pavlov's (1927) view that conditioning with long conditioned stimuli involves the acquisition of response tendencies in the early portion of the stimulus that are subsequently suppressed by the development of an inhibitory process.

Reinstatement of short-latency responses after asymptotic Pavlovian conditioning training by the presentation of an extraneous stimulus

The purpose of this study was to examine whether the progressive disappearance of short-latency conditioned responses, or inhibition of delay, observed in Pavlovian conditioning with long inter-stimulus intervals, could be reverted by the presentation of a novel stimulus. In one experiment, two groups of rabbits received extensive training with a short (250 ms) or a long (1500 ms) tone that overlapped and terminated with a periorbital shock unconditioned stimulus. After training, the presentation of an extraneous stimulus prior to tone onset produced a reinstatement of short latency CRs in the group trained with the long CS, but did not affect CR latency in the group trained with the short CS. This finding is consistent with Pavlov's (1927) view that conditioning with long conditioned stimuli involves the acquisition of response tendencies in the early portion of the stimulus that are subsequently suppressed by the development of an inhibitory process.

Habituation of the eyeblink response in humans with stimuli presented in a sequence of incremental intensity.

In an experiment we examined whether the repeated presentation of tones of gradually increasing intensities produces greater decrement in the eyeblink reflex response in humans than the repetition of tones of constant intensities. Two groups of participants matched for their initial level of response were exposed to 110 tones of 100-ms duration. For the participants in the incremental group, the tones increased from 60- to 90- dB in 3-dB steps, whereas participants in the constant group received the tones at a fixed 90-dB intensity. The results indicated that the level of response in the last block of 10 trials, in which both groups received 90-dB tones, was significantly lower in the incremental group than in the constant group. These findings support the data presented by Davis and Wagner (7) with the acoustic response in rats, but differ from several reports with autonomic responses in humans, where the advantage of the incremental condition has not been observed unambiguously. The discussion analyzes theoretical approaches to this phenomenon and the possible involvement of separate neural circuits.

Habituation of the eyeblink response in humans with stimuli presented in a sequence of incremental intensity

In an experiment we examined whether the repeated presentation of tones of gradually increasing intensities produces greater decrement in the eyeblink reflex response in humans than the repetition of tones of constant intensities. Two groups of participants matched for their initial level of response were exposed to 110 tones of 100-ms duration. For the participants in the incremental group, the tones increased from 60- to 90- dB in 3-dB steps, whereas participants in the constant group received the tones at a fixed 90-dB intensity. The results indicated that the level of response in the last block of 10 trials, in which both groups received 90-dB tones, was significantly lower in the incremental group than in the constant group. These findings support the data presented by Davis and Wagner (7) with the acoustic response in rats, but differ from several reports with autonomic responses in humans, where the advantage of the incremental condition has not been observed unambiguously. The discussion analyzes theoretical approaches to this phenomenon and the possible involvement of separate neural circuits.

Psychology and natural disasters: earthquake and tsunami in Chile on February 27, 2010 / Psicología y desastres naturales: terremoto y tsunami: del 27 de febrero de 2010 en Chile

Esta edición especial de Terapia Psicológica surge como un intento por sistematizar la información preliminar recolectada por investigadores acerca de las consecuencias psicológicas del desastre natural ocurrido en la zona centro sur de Chile el 27 de Febrero de 2010. Esta edición también se focaliza en las formas de intervención psicológica que se han aplicado en la distintas zonas devastadas, enfatizándose, además, la necesidad de concebir intervenciones para los efectos de mediano y largo plazo de este fenómeno. Por último, se revisan estrategias utilizadas en otros países para abordar desastres naturales.

This special issue of Terapia Psicológica is an attempt to organize preliminary information collected by researchers on the psychological consequences of the natural disaster occurred in the south central zone of Chile on February 27, 2010. This issue is also focused on the types of psychological interventions that have been conducted in the affected zones, also emphasizing the need to define intervention strategies for middle- and long-term effects of this phenomenon. Finally, some intervention strategies applied in other countries are reviewed.

Asociaciones excitatorias entre el contexto y la consecuencia en la reinstalación de respuestas extinguidas en el aprendizaje causal humano / Excitatory context-consequence associations in the reinstatement of extinguished responses in human causal learning

En dos experimentos, estudiantes universitarios aprendieron una relación predictiva entre un evento y una consecuencia, la que posteriormente fue extinguida presentando el evento sin la consecuencia. En el Experimento 1, se presentó la consecuencia por sí sola después de la extinción, ocasionando la reaparición de la relación predictiva aprendida originalmente, asemejándose al fenómeno del condicionamiento Pavloviano conocido como "reinstalación". Este experimento demostró además, que no es necesario apelar a asociaciones inhibitorias para explicar la reinstalación, sino que solamente a asociaciones excitatorias entre el contexto y la consecuencia. El Experimento 2 confirmó la generalidad de estos hallazgos utilizando otro procedimiento de aprendizaje causal. Se discuten estos hallazgos en términos de las diferencias entre el aprendizaje causal y el condicionamiento Pavloviano y de la posible existencia de dos mecanismos alternativos de extinción: desaprendizaje para extinguir asociaciones no consolidadas e inhibición para las consolidadas.

In two experiments, undergraduates learned a predictive relationship between an event and a consequence, which was subsequently extinguished by presenting the event without the consequence. In Experiment 1, participants were exposed to the consequence by itself after extinction, occasioning the reappearance of the originally learned predictive relationship, resembling a phenomenon known as Reinstatement in the field of Pavlovian conditioning. This experiment further demonstrated that reinstatement can be explained without appealing to inhibitory associations, but only by mean of excitatory associations between the context and the consequence. Experiment 2 confirmed the generality of these findings using a different procedure of causal learning. The findings are discussed in terms of differences between Pavlovian conditioning and causal learning and of the possible existence of two mechanisms of extinction: unlearning to extinguish non consolidated associations and inhibition for the consolidated associations.

Generality of the summation effect in human causal learning.

Considerable research has examined the contrasting predictions of the elemental and configural association theories proposed by Rescorla and Wagner (1972) and Pearce (1987), respectively. One simple method to distinguish between these approaches is the summation test, in which the associative strength attributed to a novel compound of two separately trained cues is examined. Under common assumptions, the configural view predicts that the strength of the compound will approximate to the average strength of its components, whereas the elemental approach predicts that the strength of the compound will be greater than the strength of either component. Different studies have produced mixed outcomes. In studies of human causal learning, Collins and Shanks (2006) suggested that the observation of summation is encouraged by training, in which different stimuli are associated with different submaximal outcomes, and by testing, in which the alternative outcomes can be scaled. The reported experiments further pursued this reasoning. In Experiment 1, summation was more substantial when the participants were trained with outcomes identified as submaximal than when trained with simple categorical (presence/absence) outcomes. Experiments 2 and 3 demonstrated that summation can also be obtained with categorical outcomes during training, if the participants are encouraged by instruction or the character of training to rate the separately trained components with submaximal ratings. The results are interpreted in terms of apparent performance constraints in evaluations of the contrasting theoretical predictions concerning summation.

Stimulus specificity in the acquisition and extinction of conditioned taste aversion.

An experiment evaluated whether the acquisition and extinction of conditioned taste aversion in the rat is stimulus-specific by testing the degree of response transfer between sweet and salty tastes. Animals in the paired-same and paired-different groups received a presentation of a gustatory CS and a cyclophosphamide injection US. Nonconditioned control groups received unpaired CS /US presentations or the CS followed by a vehicle injection. Taste avoidance was evaluated in three nonreinforced test sessions. In the paired-same, unpaired and vehicle groups, all test sessions were conducted with the same flavor as originally used in training, whereas the paired-different group was tested with a novel flavor on the first and second sessions and with the originally trained flavor in last session. Stimulus specific acquisition was apparent in the first test session, when the animals in the group paired-same exhibited lower fluid intake than the other three groups. Evidence of specificity of extinction was apparent in the last test session, when animals in the group paired-different exhibited lower fluid intake than the other three groups. These results provide further evidence of stimulus specificity in acquisition and extinction of conditioned taste aversion, supporting the associative interpretation of these phenomena.

[Development of a computer program to simulate the predictions of the replaced elements model of Pavlovian conditioning]. / Desarrollo de un programa computacional para simular las predicciones del modelo de elementos reemplazados (REM) de condicionamiento pavloviano.

Despite of the apparent simplicity of Pavlovian conditioning, research on its mechanisms has caused considerable debate, such as the dispute about whether the associated stimuli are coded in an "elementistic"(a compound stimuli is equivalent to the sum of its components) or a "configural" (a compound stimuli is a unique exemplar) fashion. This controversy is evident in the abundant research on the contrasting predictions of elementistic and the configural models. Recently, some mixed solutions have been proposed, which, although they have the advantages of both approaches, are difficult to evaluate due to their complexity. This paper presents a computer program to conduct simulations of a mixed model ( replaced elements model or REM). Instructions and examples are provided to use the simulator for research and educational purposes.

Enhancement of Pavlovian conditioned immunosuppression in rats.

The goal of this study was to define conditions under which conditioned immunosuppression may be observed reliably. In three experiments, rats were exposed to a gustatory conditioned stimulus (CS) paired with cyclophosphamide (US), which induces immunosuppression and malaise. In Experiment 1, a single pairing of the CS with low, medium, or high doses of cyclophosphamide in separate groups produced no reliable conditioned immunosuppression even though conditioned taste aversion was observed in groups trained with high and medium doses of CY. Experiment 2 replicated the lack of effect following a single pairing of the CS with the medium dose of cyclophosphamide but demonstrated that three pairings are sufficient to induce conditioned immunosuppression. Experiment 3 demonstrated that significant immunosuppression is observable following a single CS-US pairing if the CS is presented in compound with a previously nonreinforced CS during training, an effect reminiscent of supernormal conditioning. These findings indicate that conditioned immunosuppression effects can be enhanced in magnitude through the use of certain procedural techniques.

Stimulus specificity in the acquisition and extinction of conditioned taste aversion

An experiment evaluated whether the acquisition and extinction of conditioned taste aversion in the rat is stimulus-specific by testing the degree of response transfer between sweet and salty tastes. Animals in the paired-same and paired-different groups received a presentation of a gustatory CS and a cyclophosphamide injection US. Nonconditioned control groups received unpaired CS /US presentations or the CS followed by a vehicle injection. Taste avoidance was evaluated in three nonreinforced test sessions. In the paired-same, unpaired and vehicle groups, all test sessions were conducted with the same flavor as originally used in training, whereas the paired-different group was tested with a novel flavor on the first and second sessions and with the originally trained flavor in last session. Stimulus specific acquisition was apparent in the first test session, when the animals in the group paired-same exhibited lower fluid intake than the other three groups. Evidence of specificity of extinction was apparent in the last test session, when animals in the group paired-different exhibited lower fluid intake than the other three groups. These results provide further evidence of stimulus specificity in acquisition and extinction of conditioned taste aversion, supporting the associative interpretation of these phenomena.

Stimulus specificity in the habituation of the startle response in the rat.

A series of experiments evaluated whether the habituation of the startle response of the rat to tactile and auditory cues is stimulus specific. Experiment 1 showed stimulus specificity of a short-term habituation effect, whereby the startle to the second of a pair of stimuli was significantly less when the initial stimulus involved the same rather than the different modality. Experiments 2 and 3 focused on the more persistent decrement in startle that is a result of repeated stimulation, and demonstrated that such long-term habituation to the tactile and auditory stimuli contained a stimulus specific component in addition to a generalized component. The generalized habituation observed between the tactile and auditory stimuli in the three experiments may be due to an auditory accompaniment of the tactile stimulus employed. Discussion emphasized the utility of investigating habituation in a preparation with robust specificity.

Quantitative models of Pavlovian conditioning.

Over the last few years, research on learning and memory has become increasingly interdisciplinary. In the past, theories of learning, as a prerogative of psychologists, were generally formulated in purely verbal terms and evaluated exclusively at the behavioral level. At present, scientists are trying to build theories with a quantitative and biological flavor, seeking to embrace more complex behavioral phenomena. Pavlovian conditioning, one of the simplest and ubiquitous forms of learning, is especially suited for this multiple level analysis (i.e., quantitative, neurobiological, and behavioral), in part because of recent discoveries showing a correspondence between behavioral phenomena and associative properties at the cellular and systems levels, and in part because of its well established quantitative theoretical tradition. The present review, examines the mayor quantitative theories of Pavlovian conditioning and the phenomena to which they have been designed to account. In order to provide researchers from different disciplines with a simple guideline about the rationale of the different theoretical choices, all the models are described through a single formalism based on the neural network connectionist perspective.

Stimulus representation in SOP: II. An application to inhibition of delay.

The componential extension of SOP accounts for conditioned response (CR) timing in Pavlovian conditioning by assuming that learning accrues with relative independence to stimulus elements that are differentially occasioned during the duration of the conditioned stimulus (CS). SOP, using a competitive learning rule and the assumption that temporal learning emerges via resolution of what is equivalent to an "AX+BX-" discrimination, predicts a progressive increase in the latency of the CR over training, or what Pavlov refer to as "inhibition of delay." Other componential models, which use noncompetitive learning rules, do not predict inhibition of delay. Either type of model makes the prediction indicated, independently of the length of the CS-unconditioned stimulus (US) interval. We report two experiments that demonstrated inhibition of delay when rabbits were trained with relatively long, but not with short, CS-US intervals. To account for this divergence, we assumed that the SOP stimulus trace involves two kinds of elements, some with a temporally distributed pattern of activity over the duration of the CS duration, and some with a randomly distributed pattern. This stimulus representation, not only allows for inhibition of delay with long but not short CS-US intervals, but in combination with SOP's performance rule deduces CR's with "Weber variability."