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.

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.

In a recent series of papers, Pearce and colleagues (e.g., Pearce, Dopson, Haselgrove, & Esber, 2012) have demonstrated a so-called "redundancy effect" in Pavlovian conditioning, which is the finding of more conditioned responding to a redundant cue trained as part of a blocking procedure (A+AX+) than to a redundant cue trained as part of a simple discrimination procedure (BY+CY-). This phenomenon presents a serious challenge for those theories of conditioning that compute learning through a global error-term. In this paper, we use the Rescorla and Wagner (1972) model as a prototypical example to demonstrate that the redundancy effect can be accounted for by this class of theories if the experimental stimuli are assumed to share a common component. We also point to some domains in which this approach leads to novel predictions that may deserve empirical evaluation. (PsycINFO Database Record

The available data on occasion setting led Susan Brandon and Allan Wagner (Brandon and Wagner, 1998; Wagner and Brandon, 2001) to formulate what has come to be known as a replaced-elements conception (REM) of context-dependent cues within the SOP model (Wagner, 1981). In the present paper, we review the development of the theory, and show how, with a few congenial assumptions about shared cues, it can address some of the major regularities concerning when the transfer of occasion setting does or does not occur. Among the particular examples are the relatively unique transfers that have been reported to occur between separate serial discriminations and between targets that have been trained with the same versus different reinforcers.

In 1968 there was a symposium at Dalhousie University, the proceedings of which were published with the title Fundamental Issues in Associative Learning. There may have been some exaggeration in the title, but there was an extraordinary shared vision among the participants about what was deemed challenging at the time, and how to approach the challenge through an invigorated investigation of Pavlovian conditioning. Especially congruent were the presentations by Leon Kamin, Robert Rescorla, and myself. An important result of the research and theorizing that followed has been the appreciation of how “expectations” shape the basic regularities of associative learning as they play out even in the simplest instances of animal behavior.

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.

Investigation of the eyeblink response of humans to auditory and tactile stimulation focused on the determinants of the so called incremental stimulus intensity effect. In Experiment 1, two groups of participants were exposed to 100 tones from 60 to 87-dB in intensity. In Group Incremental, the tones increased from 60- to 87-dB in 3-dB steps, whereas participants in Group Random received the same intensities in a pseudorandom order. The performance of the two groups was compared to Group Constant that received all 100 tones at 90-dB intensity and to a fourth group, named “Apparatus” that received no stimulation. In a subsequent testing block, the results indicated that there was less responding to a 90-dB tone in the Incremental than in the other three groups, which replicates the incremental stimulus intensity effect. The novel observation was that there was also significantly less responding in the Incremental than in the other three groups to an untrained tactile stimulus, suggesting that the differences between the conditions may have implicated differences in a more general sensitization, in addition to any differences in stimulus-specific habituation. Experiment 2 demonstrated that repetition of tones at a fixed intensity caused a decrease in responding to the tones, but also an increase in responding to a novel tactile stimulus, as compared to an untrained condition. These results are discussed in terms of the interpretation of the incremental stimulus intensity effect suggested by Davis and Wagner (1969) and the AESOP (Wagner & Brandon, 1989) treatment of habituation and sensitization.

Wir berichten über einen 42-jährigen, männlichen Patienten mit pustulösen Hautveränderungen am Hinterkopf, die während eines stationären Aufenthaltes in der Gastroenterologie zur Abklärung rezidivierender blutiger Durchfälle erstmalig auftraten und sich rasch zu größenprogredienten, schmerzhaften Ulzerationen entwickelten. Nach Ausschluss anderer ulzerativer Prozesse stellten wir die Diagnose eines Pyoderma gangraenosum (PG). Die durchgeführte Diagnostik ergab als zugrunde liegende Erkrankung eine Colitis ulcerosa (CU). Eine systemische Glukokortikoidtherapie, begleitet von einer Mesalazingabe speziell zur Behandlung der CU, und eine spätere Azathioprinmedikation führten zur Abheilung des PG.

The conditioned eyeblink response (CR) in rabbits is lateralized to the eye targeted by the unconditioned stimulus (US). However, a contralateral component has been reported during concurrent discriminative conditioning of the two eyes. The authors investigated CRs produced by both eyes during conditioning with 2 different interstimulus intervals (ISIs) in which a short conditioned stimulus (CS) was paired with a US to the left eye and a long CS was paired with a US to the right eye. Whether the 2 CSs were more or less similar (or identical), the short CS produced short-latency CRs in the left eye, whereas the long CS produced long-latency CRs in the right eye. The contralateral responses to a CS trained at one ISI were separable into temporal corollaries of the ipsilateral response (suggesting a bilaterality of the CR) versus those to a CS trained at another ISI (indicating generalization between the CSs). The results indicate that the neuronal substrates subserving CRs of the two eyes involve not only a dominant lateralization but also some avenue of bilaterality.

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.

This article presents an overview of the recent research and theoretical developments in Pavlovian conditioning. In the first section, background information is provided and three of the historically most important theoretical approaches are described: The linear rule, the delta P rule, and the Rescorla–Wagner rule. The second section is divided into seven parts, each covering an important empirical issue and the manner of theoretical solution that it has inspired. Given the general influence of the Rescorla–-Wagner model in the background, each empirical issue is presented in terms of how it has challenged the basic assumptions of that model. The issues considered include inhibitory learning during extinction, the configural versus elemental controversy, timing effects, the common fate of stimuli trained in compound, priming effects, divergence of response measures, and learning about absent cues.

In Pavlovian eyeblink conditioning, the conditioned response (CR) is highly lateralized to the eye to which the unconditioned stimulus (US) has been directed. However, the initial conditioning of one eye can facilitate subsequent conditioning of the other eye, a phenomenon known as the intereye transfer (IET) effect. Because a conditioned emotional response (CER), as well as the eyeblink CR, is acquired during eyeblink conditioning and influences the development of the CR, the CER acquired in initial training can plausibly account for the IET effect. To evaluate this possibility, the present study utilized previously determined eyeblink conditioning procedures that effectively decouple the degree of CER and CR development to investigate the IET effect. In each of 3 experiments rabbits were initially trained with comparison procedures that differentially favored the development of the eyeblink CR or the CER, prior to a shift of the US to the alternate eye. The observed differences in the IET suggest that the effect depends largely on the specific development of eyeblink CRs rather than the CER. The neurobiological implications of this apparent bilaterality of the eyeblink CR are discussed.

Kenneth Spence (1936, 1937) formalized a quantitative, elemental approach to association theory that has had a broad and dominating influence on learning theory for many years. A set of challenges to the basic approach has spurred the subsequent evolution of elemental theory in various ways. Four of the challenges and some resulting theoretical accommodations are described in the context of Pavlovian conditioning. The evolution involves departures from important specifics of Spence’s theory, but is viewed as demonstrating the utility of the basic, elemental approach that is one of his legacies.

The paper by Melchers, Shanks, and Lachnit (2007) reviews the available evidence suggesting that there is flexible processing, such that some associative learning tasks can be solved either configurally or elementally. We find the evidence provocative but limited in its demonstrated generality and silent with respect to the theoretical mechanisms that might regulate the alleged flexibility of processing. Further research is invited to determine the scope of the variation involved and how best to account for it. At present, theories, either elemental or configural, that include mechanisms to shift the weight assigned to component stimuli appear to be potential candidates for embracing the data.

Kenneth W. Spence was among the most influential learning theorists of the 20th century. He was not only a pioneer in the genesis of computational models but an articulate systematist and scholar regarding the place of theory in psychology. The following observations and remembrances were offered at the University of Iowa as part of a tribute to his contributions on the 100th anniversary of his birth.