Cody W. Polack

Extinction context as a conditioned inhibitor

Two lick suppression experiments using rats were conducted to determine whether extinction of a punctate excitor in a particular context would result in that context becoming a conditioned inhibitor, as defined by passing both summation and retardation tests. The role of extinction trial spacing was investigated as a possible determinant of whether the extinction context would become inhibitory. Experiment 1 demonstrated that, although inhibition was evident using either massed or spaced extinction trials, spaced trials reduced measurable inhibition as assessed by the summation test, but trial spacing had no influence on retardation test performance. Experiment 2 confirmed Experiment 1’s conclusions while controlling for the influence of latent inhibition on the retardation test. In Experiment 2, the context proved inhibitory only following massed extinction trials. These data suggest that, at least with select parameters, an extinction context can become inhibitory.

On the differences in degree of renewal produced by the different renewal designs.

This paper addresses sources contributing to the differences in the degree of recovery from extinction observed with different renewal paradigms. In two lick suppression experiments with rats, we assessed the role of the associative status of the acquisition context in both the weakness of AAC renewal and the sometimes observed weaker renewal resulting from an ABC design relative to an ABA design. In Experiment 1, we observed that AAC renewal relative to an AAA control group was small unless Context A had undergone associative deflation (i.e., extinction of Context A). Deflation of Context A not only decreased behavioral control by the CS in the AAA condition, but increased it in the AAC condition, thereby implicating a comparator process in addition to associative summation between the CS and test context. In Experiment 2, an excitatory acquisition context was found to enhance the difference between ABC and ABA renewal. Associative deflation of the acquisition context decreased ABA renewal more than ABC renewal. Thus, the associative value of the acquisition context (A) was more positively related to the level of renewal when the target CS (X) was tested in this context than when it was tested in a neutral but equally familiar context (C), consistent with the frequently observed greater renewal in an ABA condition than an ABC condition arising from associative summation of the CS and test context. These findings demonstrate that the excitatory status of the acquisition context influences the observed degree of renewal.

Trial frequency effects in human temporal bisection: Implications for theories of timing

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.

Associative foundation of causal learning in rats

Are humans unique in their ability to interpret exogenous events as causes? We addressed this question by observing the behavior of rats for indications of causal learning. Within an operant motor–sensory preconditioning paradigm, associative surgical techniques revealed that rats attempted to control an outcome (i.e., a potential effect) by manipulating a potential exogenous cause (i.e., an intervention). Rats were able to generate an innocuous auditory stimulus. This stimulus was then paired with an aversive stimulus. The animals subsequently avoided potential generation of the predictive cue, but not if the aversive stimulus was subsequently devalued or the predictive cue was extinguished (Exp. 1). In Experiment 2, we demonstrated that the aversive stimulus we used was in fact aversive, that it was subject to devaluation, that the cue–aversive stimulus pairings did make the cue a conditioned stimulus, and that the cue was subject to extinction. In Experiments 3 and 4, we established that the decrease in leverpressing observed in Experiment 1 was goal-directed instrumental behavior rather than purely a product of Pavlovian conditioning. To the extent that interventions suggest causal reasoning, it appears that causal reasoning can be based on associations between contiguous exogenous events. Thus, contiguity appears capable of establishing causal relationships between exogenous events. Our results challenge the widely held view that causal learning is uniquely human, and suggest that causal learning is explicable in an associative framework.

Animal models of psychopathology: Historical models and the pavlovian contribution

La investigacion con animales no humanos como sujetos experimentales, para entender el comportamiento humano, se basa en la nocion darwiniana de la continuidad de las especies. En este marco encontramos modelos analogos para entender la biologia y el comportamiento humanos en especies no humanas. En psicologia, los modelos animales han probado ser una herramienta efectiva para el entendimiento del comportamiento humano, tanto normal como anormal. En la presente revision discutimos como los modelos animales han sido usados al investigar la psicopatologia. Luego de revisar tres modelos animales historicos de psicopatologias especificas, discutimos como los fenomenos descubiertos al estudiar el condicionamiento pavloviano han contribuido a nuestra comprension de la etiologia y mantencion de la psicopatologia humana, como la tradicion pavloviana ha contribuido al desarrollo de mejores formas de tratamiento para desordenes del comportamiento, y de forma mas general, como los fenomenos pavlovianos se encuentran implicados en casi todas las interacciones entre un organismo y su ambiente.

Stepping back from ‘persistence and relapse’ to see the forest: Associative interference

Historically, there has been considerable interest in a large variety of forms of associative interference. However, various factors including interest in clinical application and perhaps recent funding priorities have resulted in a narrowed focus on one particular instance of interference, extinction, with relative neglect of other types of interference. We have been using the existing literature and conducting new experiments to determine whether there is a consistent set of rules governing the occurrence and persistence of two-phase associative interference across (a) proactive and retroactive interference, (b) cue and outcome interference, (c) the type of training in phase 1 (excitatory, inhibitory, or simple nonreinforcement), and (d) the type of training in phase 2 (excitatory, inhibitory, or simple nonreinforcement). Our hope is that a return to more general questions concerning associative interference might reveal broad truths concerning the nature of forgetting. Identifying global principles of associative interference may also help us better appreciate the nature of extinction, including how it can be enhanced and made more enduring, as well as how it can be minimized and made more fleeting.

Comparing the context specificity of extinction and latent inhibition

Exposure to a cue alone either before (i.e., latent inhibition treatment) or after (i.e., extinction) the cue is paired with an unconditioned stimulus results in attenuated conditioned responding to the cue. Here we report two experiments in which potential parallels between the context specificity of the effects of extinction and latent inhibition treatments were directly compared in a lick suppression preparation with rats. The reversed ordering of conditioning and nonreinforcement in extinction and latent inhibition designs allowed us to examine the effect of training order on the context specificity of what is learned given phasic reinforcement and nonreinforcement of a target cue. Experiment 1 revealed that when conditioned-stimulus (CS) conditioning and CS nonreinforcement were administered in the same context, both extinction and latent inhibition treatments had reduced impacts on test performance, relative to excitatory conditioning when testing occurred outside the treatment context. Similarly, Experiment 2 showed that when conditioning was administered in one context and nonreinforcement was administered in a second context, the effects of both extinction and latent inhibition treatments were attenuated when testing occurred in a neutral context, relative to the context in which the CS was nonreinforced. The observed context specificity of extinction and latent inhibition treatments has been previously reported in both cases, but not in a single experiment under otherwise identical conditions. The results of the two experiments convergently suggest that memory of nonreinforcement becomes context dependent after a cue is both reinforced and nonreinforced, independent of the order of training.

Failure to observe renewal following retrieval-induced forgetting.

Recent studies have pursued the nature of inhibition observed in retrieval-induced forgetting (RIF) tasks. In a RIF paradigm, participants are trained on category-exemplar pairs in Phase 1. Then, some exemplars from select categories (Rp+ items) receive further practice in Phase 2. At test, impaired recall for non-practiced exemplars of the practiced categories (Rp- items) is observed relative to exemplars from non-practiced categories (Nrp items). This difference constitutes RIF. Prior reports of spontaneous recovery from RIF indicate that RIF represents a lapse rather than a loss of memory. Empirical analogs and theoretical considerations suggest that RIF should also be reversible through a change of context between Phase 2 and testing (i.e., renewal). We conducted two experiments using human participants to evaluate the context dependency of RIF. In both experiments, Phases 1 and 2 occurred in distinctly different contexts with subsequent testing occurring in either the Phase 1 context or the Phase 2 context. RIF was observed in both experiments. Experiment 1 additionally found that the magnitude of RIF was not reduced by testing in the Phase 1 context relative to testing in the Phase 2 context. Experiment 2 further tested context dependency of RIF by (1) increasing the dissimilarity between the two contexts and (2) inserting a retention interval between Phase 2 and test for half of the participants in each test context condition. The data again indicated no effect of the context manipulation. Thus, no renewal from RIF was observed in either experiment; moreover, these null findings were supported by Bayesian analyses. These results are compared with analogous inhibitory processes in the animal memory literature that typically show both physical and temporal context dependency.

Retrieval-induced versus context-induced forgetting: Does retrieval-induced forgetting depend on context shifts?

Retrieval-induced forgetting (RIF) is the observation that retrieval of target information causes forgetting of related nontarget information. A number of accounts of this phenomenon have been proposed, including a context-shift-based account (Jonker, Seli, & Macleod, 2013). This account proposes that RIF occurs as a result of the context shift from study to retrieval practice, provided there is little context shift between retrieval practice and test phases. We tested both claims put forth by this context account. In Experiment 1, we degraded the context shift between study and retrieval practice by implementing a generative study condition that was highly similar to retrieval practice. We observed no degradation of RIF for these generated exemplars relative to a conventional study control. In Experiment 2, we conceptually replicated the finding of RIF following generative study, and tested whether context differences between each of the three phases affected the size of RIF. Our findings were again contrary to the predictions of the context account. Conjointly, the 2 experiments refute arguments about the potential inadequacy of our context shifts that could be used to explain either result alone. Overall, our results are most consistent with an inhibitory account of RIF (e.g., Anderson, 2003).

Associative structure of integrated temporal relationships.

According to the temporal-coding hypothesis (TCH; Savastano & Miller, Behavioural Processes 44:147–162, 1998), acquired associations include temporal information concerning the interval between the associated elements. Moreover, the TCH posits that subjects can integrate two independently acquired associations that share a common element (e.g., S2–S1 and S1–US), which results in the creation of a third association with its own temporal relationship (S2–US). Some evidence has suggested that such temporal integration occurs at the time of testing (Molet, Miguez, Cham, & Miller, Journal of Experimental Psychology: Animal Behavior Processes 38:369–380, 2012). Here we report two fear-conditioning experiments with rats conducted to identify the associative structure of the integrated temporal relationship. The goal was to distinguish between two possible associative structures that could exist following an initial test on which temporal integration occurs: (1) Conditioned responding to S2 on subsequent tests could be the result of recurring successive activation of two independently learned temporal maps that remain independently stored in memory (i.e., S2–S1 plus S1–US). (2) Temporal integration at the moment of initial testing could result in the formation of a direct S2–US (or S2–response) temporal map. Integration was found to occur at test and to produce a new association that was independent of associations with the common element (S1). However, the associative status of S1 appeared to modulate whether or not the new association with S2 was US-specific (S2–US) or directly activated a fear response (S2–response).