Reflections on human pavlovian decelerative heart-rate conditioning with negative tilt as US: Alternative approaches

The negative-tilt preparation that has been reported since the late seventies is a specific form of Pavlovian conditioning that is of scientific interest and has potential applications. In this paper I reflect on the usefulness, to the development of this preparation, of two approaches to Pavlovian conditioning. One approach is the older S-R learning, stimulus-substitution paradigm exemplified by learning texts of the sixties. The other is the modern, Tolman-like view, according to which the phenomenon of Pavlovian conditioning is “now described as the learning of relations among events so as to allow the organism to represent its environment.” The three assumptions encapsulated by this approach are: (a) that only CS-US contingency relations are learned; (b) that teleological modes of explanations are adequate; (c) that the representational theory of knowledge is sound. Concerning Pavlovian conditioning in general, questions been raised in the literature for all three assumptions; they have not been adequately answered. Regarding the specific problem of developing the human Pavlovian heart-ratedecelerative conditioning with negative tilt as the US, I suggest that the cognitive approach has been much less helpful than the older, S-R, stimulus-substitution paradigm. Nevertheless, other literature clearly indicates that the cognitive, S-S approach has generated considerable interest and research, especially in preparations like the conditioned emotional response (CER), which are CS-IR ones in the sense that the effects on the CR are assessed indirectly through measuring an indicator or instrumental response (IR). Finally, even in CS-CR preparations like human GSR conditioning, it is important to study the cognitive, S-S learning process through using such dependent variables as continuously assessed subjective CS-US contingency.     

Some recalcitrant views on the role of noncognitive S-R factors in human Pavlovian autonomic conditioning. Some facts still haunt us

Either implicitly or explicity, most workers in the last two decades have adopted the (imperialistic) view that conditioning is simply the learning of (cognitive) S-S relationships, and that (noncognitive) S-R factors are irrelevant. I shall remind us of some contrary evidence from human Pavlovian autonomic conditioning (HPAC), consideration of which may spoil our neat cognitive picture (representation?) of the world, but may also lead both to a better understanding of the conditioning phenomenon and to more genuinely useful applications of conditioning principles to behavioral (including psychophysiological) problems.     

Some recalcitrant views on the role of noncognitive S-R factors in human pavlovian autonomic conditioning

Either implicitly or explicitly, most workers in the last two decades have adopted the (imperialistic) view that conditioning is simply the learning of (cognitive) S-S relationships, and that (noncognitive) S-R factors are irrelevant. I shall remind us of some contrary evidence from human Pavlovian autonomic conditioning (HPAC), consideration of which may spoil our neat cognitive picture (representation?) of the world, but may also lead both to a better understanding of the conditioning phenomenon and to more genuinely useful applications of conditioning principles to behavioral (including psychophysiological) problems.     

The effect of CS-US contingency variation on GSR and on subjective CS-US relational awareness

Ninety subjects were tested in a single-cue Pavlovian conditioning paradigm involving three groups which differed with regard to the contingency relationship between CS and US (negative contingency, zero contingency, positive contingency). To examine the relationship between conditioned GSR performance and subject’s cognitive beliefs regarding the CS-US relationship, both GSR and CS-US relational learning were constantly measured on a continuous scale over the entire experimental session. The data suggest the independence of autonomic and cognitive responding in the single-cue Pavlovian paradigm.     

When All Is Still Concealed: Are We Closer to Understanding the Mechanisms Underlying Evaluative Conditioning?

Fulcher and Hammerl's (2001) important exploration of the role of contingency awareness in evaluative conditioning (EC) raises a lot of issues for discussion: (1) what boundaries, if any, exist between EC and affective learning paradigms?; (2) if EC does occur without awareness does this mean it is nonpropositional learning?; (3) is EC driven by stimulus-response (S-R), rather than stimulus-stimulus (S-S), associations and if so should it then surprise us that contingency awareness is not important?; and (4) if S-R associations are at the heart of EC, should we automatically assume EC is part of a different learning mechanism to autonomic Pavlovian conditioning (Field, 2000a, 2000b)? This article, after a critical review of Fulcher and Hammerl's work, discusses these issues with reference to what can be realistically inferred about the mechanisms underlying EC.     

Direct and continuous measurement of relational learning in human pavlovian conditioning

Three experiments were conducted employing a continuous measure of conditional stimulus/unconditional stimulus (CS/US) contingencies as perceived by the subject (i.e., subjective contingency or SC). It is argued that direct measurement of relational learning, as indexed by SC, can lead to a better understanding of Pavlovian conditioning processes. The first two experiments applied this approach to a methodologic controversy, raising the debate from a procedure-based argument to testing what the subject actually learns about CS/US relationships. While the issue was not resolved, testable hypotheses for future research were generated from the data. The third experiment contrasted the contingency stimulus-stimulus (S-S) account of Pavlovian conditioning with an earlier stimulus-response (S-R) continguity-reinforcement account. In this experiment, both SC and skin resistance were measured. Evidence for the existence of both cognitive-propositional and response-learning processes in conditioning was obtained.     

Backward conditioning in Pavlovian type studies

Authors of almost all learning texts have indicated that unconditional/ stimulus-conditional stimulus (UCS-CS) trials (backward conditioning) utilized in classical conditioning experiments will not result in establishing a conditional response (CR) (excitation). Recently, it has been proposed that backward conditioning can take place although whether UCS-CS trials result in excitation or inhibition has been left unspecified. It is proposed that the diversity of findings can be attributed to inadequate methodology and the use of a classical-instrumental transfer paradigm. When only traditional Pavlovian conditioning studies are examined, the experimental findings suggest that UCS-CS trials will result in inhibition.     

Pavlovian conditioning of Hermissenda: current cellular, molecular, and circuit perspectives

The less-complex central nervous system of many invertebrates make them attractive for not only the molecular analysis of the associative learning and memory, but also in determining how neural circuits are modified by learning to generate changes in behavior. The nudibranch mollusk Hermissenda crassicornis is a preparation that has contributed to an understanding of cellular and molecular mechanisms of Pavlovian conditioning. Identified neurons in the conditioned stimulus (CS) pathway have been studied in detail using biophysical, biochemical, and molecular techniques. These studies have resulted in the identification and characterization of specific membrane conductances contributing to enhanced excitability and synaptic facilitation in the CS pathway of conditioned animals. Second-messenger systems activated by the CS and US have been examined, and proteins that are regulated by one-trial and multi-trial Pavlovian conditioning have been identified in the CS pathway. The recent progress that has been made in the identification of the neural circuitry supporting the unconditioned response (UR) and conditioned response (CR) now provides for the opportunity to understand how Pavlovian conditioning is expressed in behavior.     

Signalization and stimulus-substitution in Pavlov's theory of conditioning

The concept of conditioning as signalization proposed by Ivan P. Pavlov (1927, 1928) is studied in relation to the theory of stimulus-substitution, which is also attributed to him. In the so-called theory of stimulus-substitution a distinction must be made between an empirical principle of substitution and an actual theory of substitution, which can adopt different forms. The Pavlovian theory of substitution--which conceives substitution as a substitution of the unconditioned stimulus (US) by the conditioned stimulus (CS) in the activation of the representation of the former--can be understood as an explanation or model of signalization. Signalization and substitution are answers to different questions, and the level of analysis to which signalization corresponds, is that which concerns the nature of conditioning as an operation of the animal in the environment.     

Pavlov and the foundation of behavior therapy

The foundation, achievements, and proliferation of behavior therapy have largely been fueled by the movement's foundation in behavioral principles and theories. Although behavioral accounts of the genesis and treatment of psychopathology differ in the extent to which they emphasize classical or operant conditioning, the mediation of cognitive factors, and the role of biological variables, Pavlov's discovery of conditioning principles was essential to the founding of behavior therapy in the 1950s, and continues to be central to modern behavior therapy. Pavlov's reliance on a physiological model of the nervous system, sensible in the context of an early science of neurology, has had an implication for behavior therapists interested in the study of personality types. However, Pavlov's major legacy to behavior therapy was his discovery of "experimental neuroses," shown by his students Eroféeva and Shenger-Krestovnikova, to be produced and eliminated through the principles of conditioning and counter-conditioning. This discovery laid the foundation for the first empirically-validated behavior therapy procedure, systematic desensitization, pioneered by Wolpe. The Pavlovian origins of behavior therapy are analyzed in this paper, and the relevance of conditioning principles to modern behavior therapy is demonstrated. It is shown that Pavlovian conditioning represents far more than a systematic basic learning paradigm. It is also an essential theoretical foundation for the theory and practice of behavior therapy.     

The role of information about the response-outcome relation in instrumental discrimination learning

In 4 instrumental learning experiments, the hierarchical organization among responses (R), outcomes (O), and stimuli (S) was examined. Each experiment explored the possibility that S becomes associated with the R-O relation by providing information about that relation. In each case, an analogy was developed to a paradigm that has been important for concluding that informational relations affect Pavlovian conditioning. Experiments 1 and 2 found an effect of the information that S provides about the R-O relation, using paradigms analogous to blocking and contingency experiments. Experiments 3 and 4 demonstrated a similar result, using a paradigm like that of relative validity. In each case, the experiments pointed to the importance of the information that S gives about the R-O relation, rather than about the individual R and O elements.     

The S-R Information Stream: Where's the Filter?

Pavlovian conditioning procedures, in which events such as tastes, lights, and sounds become predictors of food, water, and shocks, have been used for studying the role of the information filter in the selection of conditioned responses. Different models posit the filter at different locations in the S-R stream, but most models suggest either a pre-encoding filter, in which much information is discarded at an early stage of processing, or a post-encoding filter, in which the information is stored but not subsequently expressed in behavior. A selective review of the literature on cue-competition effects reveals a plethora of phenomena that support a post-encoding, but not a pre-encoding filter in Pavlovian processes.     

The S-R information stream: Where’s the filter?

Pavlovian conditioning procedures, in which events such as tastes, lights, and sounds become predictors of food, water, and shocks, have been used for studying the role of the information filter in the selection of conditioned responses. Different models posit the filter at different locations in the S-R stream, but most models suggest either a pre-encoding filter, in which much information is discarded at an early stage of processing, or a post-encoding filter, in which the information is stored but not subsequently expressed in behavior. A selective review of the literature on cue-competition effects reveals a plethora of phenomena that support a post-encoding, but not a pre-encoding filter in Pavlovian processes.     

S-R associations, their extinction, and recovery in an animal model of anxiety: a new associative account of phobias without recall of original trauma

Associative accounts of the etiology of phobias have been criticized because of numerous cases of phobias in which the client does not remember a relevant traumatic event (i.e., Pavlovian conditioning trial), instructions, or vicarious experience with the phobic object. In three lick suppression experiments with rats as subjects, we modeled an associative account of such fears. Experiment 1 assessed stimulus-response (S-R) associations in first-order fear conditioning. After behaviorally complete devaluation of the unconditioned stimulus, the target stimulus still produced strong conditioned responses, suggesting that an S-R association had been formed and that this association was not significantly affected when the outcome was devalued through unsignaled presentations of the unconditioned stimulus. Experiments 2 and 3 examined extinction and recovery of S-R associations. Experiment 2 showed that extinguished S-R associations returned when testing occurred outside of the extinction context (i.e., renewal) and Experiment 3 found that a long delay between extinction and testing also produced a return of the extinguished S-R associations (i.e., spontaneous recovery). These experiments suggest that fears for which people cannot recall a cause are explicable in an associative framework, and indicate that those fears are susceptible to relapse after extinction treatment just like stimulus-outcome (S-O) associations.     

Differential effects of forward or simultaneous conditioned stimulus-unconditioned stimulus intervals on the defensive behavior system of the Norway rat (Rattus norvegicus)

To test several predictions derived from a behavior-systems approach, the authors assessed Pavlovian fear conditioning in rats after 30 trials of forward, simultaneous, or unpaired training. Direct evidence of conditioned fear was collected through observation of flight and freezing reactions during presentations of the conditioned stimulus (CS) alone. The authors also tested the CS's potential to reinforce an instrumental escape response in an escape-from-fear paradigm. On the one hand, rats that received forward training showed conditioned freezing, but no conditioned flight was observed. On the other hand, rats that received simultaneous training showed conditioned flight, but no conditioned freezing was observed. Rats that received either forward or simultaneous pairings showed instrumental learning of the escape-from-fear response. Implications for several theories of Pavlovian conditioning are discussed.     

Reasoning rats: forward blocking in Pavlovian animal conditioning is sensitive to constraints of causal inference

Forward blocking is one of the best-documented phenomena in Pavlovian animal conditioning. According to contemporary associative learning theories, forward blocking arises directly from the hardwired basic learning rules that govern the acquisition or expression of associations. Contrary to this view, here the authors demonstrate that blocking in rats is flexible and sensitive to constraints of causal inference, such as violation of additivity and ceiling considerations. This suggests that complex cognitive processes akin to causal inferential reasoning are involved in a well-established Pavlovian animal conditioning phenomenon commonly attributed to the operation of basic associative processes.     

Is the devil in the detail? Evidence for S-S learning after unconditional stimulus revaluation in human evaluative conditioning under a broader set of experimental conditions

Whether valence change during evaluative conditioning is mediated by a link between the conditional stimulus (CS) and the unconditional stimulus (US; S-S learning) or between the CS and the unconditional response (S-R learning) is a matter of continued debate. Changing the valence of the US after conditioning, known as US revaluation, can be used to dissociate these accounts. Changes in CS valence after US revaluation provide evidence for S-S learning but if CS valence does not change, evidence for S-R learning is found. Support for S-S learning has been provided by most past revaluation studies, but typically the CS and US have been from the same stimulus category, the task instructions have suggested that judgements of the CS should be based on the US, and USs have been mildly valenced stimuli. These factors may bias the results in favour of S-S learning. We examined whether S-R learning would be evident when CSs and USs were taken from different categories, the task instructions were removed, and more salient USs were used. US revaluation was found to influence explicit US evaluations and explicit and implicit CS evaluations, supporting an S-S learning account and suggesting that past results are stable across procedural changes.     

The effects of postconditioning revaluation of CS1 and UCS following pavlovian second-order electrodermal conditioning in humans

An experiment is described which uses various inferential post-conditioning revaluation techniques in order to clarify the associative substructure underlying Pavlovian electrodermal conditioning in human subjects. This study established a second-order skin conductance response (SCR) by pairing a CS₁ with an aversive 115 dB tone (UCS), and then pairing a different stimulus (CS₂) with CS₁. The second-order SCR survived post-conditioning extinction of the response to CS₁, but was abolished when (i) a post-conditioning habituation procedure resulted in a favourable revaluation of the tone UCS, or (ii) when subjects were given instructions which informed them that there would be no more UCS presentations. These results suggest that in the second-order electrodermal conditioning paradigm described, CR₂ is not mediated by S-R links--as it appears to be in second-order aversive conditioning in nonhuman animals--but is affected by manipulations which modify the subject's cognitions concerning the UCS.     

Predicting danger: the nature, consequences, and neural mechanisms of predictive fear learning

The ability to detect and learn about the predictive relations existing between events in the world is essential for adaptive behavior. It allows us to use past events to predict the future and to adjust our behavior accordingly. Pavlovian fear conditioning allows anticipation of sources of danger in the environment. It guides attention away from poorer predictors toward better predictors of danger and elicits defensive behavior appropriate to these threats. This article reviews the differences between learning about predictive relations and learning about contiguous relations in Pavlovian fear conditioning. It then describes behavioral approaches to the study of these differences and to the examination of subtle variations in the nature and consequences of predictive learning. Finally, it reviews recent data from rodent and human studies that have begun to identify the neural mechanisms for direct and indirect predictive fear learning.     

Examining the sex- and circadian dependency of a learning phenotype in mice with glycine transporter 1 deletion in two Pavlovian conditioning paradigms

Behavioural characterisation of transgenic mice has been instrumental in search of therapeutic targets for the modulation of cognitive function. However, little effort has been devoted to phenotypic characterisation across environmental conditions and genomic differences such as sex and strain, which is essential to translational research. The present study is an effort in this direction. It scrutinised the stability and robustness of the phenotype of enhanced Pavlovian conditioning reported in mice with forebrain neuronal deletion of glycine transporter 1 by evaluating the possible presence of sex and circadian dependency, and its consistency across aversive and appetitive conditioning paradigms. The Pavlovian phenotype was essentially unaffected by the time of testing between the two circadian phases, but it was modified by sex in both conditioning paradigms. We observed that the effect size of the phenotype was strongest in female mice tested during the dark phase in the aversive paradigm. Critically, the presence of the phenotype in female mutants was accompanied by an increase in resistance to extinction. Similarly, enhanced conditioned responding once again emerged solely in female mutants in the appetitive conditioning experiment, which was again associated with an increased resistance to extinction across days, but male mutants exhibited an opposite trend towards facilitation of extinction. The present study has thus added hitherto unknown qualifications and specifications of a previously reported memory enhancing phenotype in this mouse line by identifying the determinants of the magnitude and direction of the expressed phenotype. This in-depth comparative approach is of value to the interpretation of behavioural findings in general.