Similarities between Pavlovian conditioning in nonhumans and causal judgment by humans suggest that similar processes operate in these situations. Notably absent among the similarities is backward blocking (i.e., retrospective devaluation of a signal due to increased valuation of another signal that was present during training), which has been observed in causal judgment by humans but not in Pavlovian responding by animals. The authors used rats to determine if this difference arises from the target cue being biologically significant in the Pavlovian case but not in causal judgment. They used a sensory preconditioning procedure in Experiments 1 and 2, in which the target cue retained low biological significance during the treatment, and obtained backward blocking. The authors found in Experiment 3 that forward blocking also requires the target cue to be of low biological significance. Thus, low biological significance is a necessary condition for a stimulus to be vulnerable to blocking. In recent years, numerous researchers have remarked on the similarity of the conditions that encourage the acquisition of causal relationships in humans and those that foster

Associative learning theories assume that cue interaction and, specifically, retrospective revaluation occur only when the target cue is previously trained in compound with the to-be-revalued cue. However, there are recent demonstrations of retrospective revaluation in the absence of compound training (e.g., Matute & Pineño, 1998a, 1998b). Nevertheless, it seems reasonable to assume that cue interaction should be stronger when the cues are trained together than when they are trained apart. In two experiments with humans, we directly compared compound and elemental training of cues. The results showed that retrospective revaluation in the elemental condition can be as strong as and, sometimes, stronger than that in the compound condition. This suggests that within-compound associations are not necessary for retrospective revaluation to occur and that these effects can possibly be best understood in the framework of general interference theory. In the literature of animal conditioning and human associative learning, it is well known that if a cue, X, is consistently followed by an outcome, O (i.e., X–O), X is generally learned as a predictor of the occurrence of the outcome. It is also well known that responding to X in a subsequent test phase becomes altered if another cue, A, is trained in compound with X as a predictor of the same outcome. Some classic instances of these cue interaction effects in the animal learning literature are overshadowing (Pavlov, 1927), blocking (Kamin, 1968), conditioned inhibition (Pavlov, 1927), and the relative stimulus validity

The impairment in responding to a secondly trained association because of the prior training of another (i.e., proactive interference) is a well-established effect in human and animal research, and it has been demonstrated in many paradigms. However, learning theories have been concerned with proactive interference only when the competing stimuli have been presented in compound at some moment of the training phase. In this experiment we investigated the possibility of proactive interference between elementally-trained stimuli at the acquisition and at the retrieval stages in a behavioral task with humans. After training a cue-outcome association we observed retardation in the acquisition of an association between another cue and the same outcome. Moreover, after asymptotic acquisition of the secondly trained association, impairment of retrieval of this secondly trained association was also observed. This finding of proactive interference between elementally-trained cues suggests that interference in predictive learning and other traditional interference effects could be integrated into a common framework. Interference among cues is a central topic in associative learning research. Cue interference is well represented by Kamin’s early studies (e.g., 1968) with rats, where he found that the training of two cues in compound after the isolated

In the analysis of stimulus competition in causal judgment, 4 variables have been frequently confounded with respect to the conditions necessary for stimuli to compete: causal status of the competing stimuli (causes vs. effects), temporal order of the competing stimuli (antecedent vs. subsequent) relative to the noncompeting stimulus, directionality of training (predictive vs. diagnostic), and directionality of testing (predictive vs. diagnostic). In a factorial study using an overshadowing preparation, the authors isolated the role of each of these variables and their interactions. The results indicate that competition may be obtained in all conditions. Although some of the results are compatible with various theories of learning, the observation of stimulus competition in all conditions calls for a less restrictive reformulation of current learning theories that allows similar processing of antecedent and subsequent events, as well as of causes and effects. Stimulus competition is defined as the phenomenon in which responding to a target stimulus (X), on the basis of its signaling some event, is weakened as a consequence of X’s being trained in the presence of another stimulus (A) that better signals the same

Reversal from blocking in humans as a result of posttraining extinction of the blocking stimulus FRANCISCO ARCEDIANO, MARTHA ESCOBAR, and HELENA MATUTE Universidad de Deusto, Bilbao, Spain In a blocking procedure, conditioned stimulus (CS) A is paired with the unconditioned stimulus (US) in Phase 1, and a compound of CSs A and X is then paired with the US in Phase 2. The usual result of such a treatment is that X elicits less conditioned responding than if the A–US pairings of Phase 1 had not occurred. Obtaining blocking with human participants has proven difficult, especially if a behavioral task is used or if the control group experiences reinforcement of a CS different from the blocking CS in Phase 1. In the present series, in which human participants and a behavioral measure of learning were used, we provide evidence of blocking, using the above described control condition. Most important, we demonstrate that extinction of the blocking CS (A) following blocking treatment reverses the blocking deficit (i.e., increases responding to X). These results are at odds with traditional associative theories of learning, but they support current associative theories that predict that posttraining manipulations of the competing stimulus can result in a reversal of stimulus competition phenomena.

Despite the many demonstrations of blocking in animals, there is still little evidence of blocking with human subjects, which is problematic for general learning and behavior theory. The purpose of this research was to examine blocking with human subjects using a design and behavioral procedure (conditioned suppression) similar to those commonly used in animal research. First, subjects learned an operant task. Later, they were instructed to suppress responding when a visual US was presented. Two Pavlovian acquisition phases and a test phase occurred while the subjects were performing the operant task. In the first Pavlovian phase, CS A predicted the US for the experimental group, but was uncorrelated with the US for the control group. In the second Pavlovian phase, a compound CS AX predicted the US for both groups. At test, CS X was presented to all subjects and suppression ratios were assessed. Experimental subjects suppressed responding in the presence of CS X less than did control subjects, thereby demonstrating a blocking effect. This research, in demonstrating blocking in humans, adds to the known similarities in animal and human behavior. � 1997 Academic Press Since Kamin described the blocking effect in 1968, this effect has been investigated primarily with rats and other nonhuman animals as experimental subjects. In a traditional blocking procedure, there are two acquisition phases. In the first phase, the experimental group is exposed to a conditioned stimulus

“that process which manifests itself by adaptive changes in individual behaviour as a result of experience. ” Thorpe (1963) Manning and Dawkins (1992), and their more recent edition, both state that the old approach to learning has “been replaced by a much more biologically based approach.... learning is now seen as a way in which animals attempt to identify key aspects of a fluctuating environment: to detect its regularities and ignore the distracting ‘noise ’ which is not important for them.” My aim in these lectures is to discuss how animals pick out the relevant detail and much of the material is drawn from a classic book by Dickinson (1980) recommended by Manning and Dawkins. The ideas in the book are important but it is a hard read. I have tried to extract the best bits and place them in an intelligible framework. That means I have had to skip many other aspects of learning and memory but these are covered by Manning and Dawkins (1992) and in other introductory texts. Most of these commend the modern approach but make no attempt to explain it. An exception is Pearce (1997, Chapter 3) which gives a good account of theoretial developments since