Within-compound associations in retrospective revaluation and in direct learning: A challenge for comparator theory

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.

What is the value of an action that has never been tried before? One way to frame this question is as an inductive problem: how can I generalize my previous experience with one set of actions to a novel action? We show how hierarchical Bayesian inference can be used to solve this problem, and describe an equivalence between the Bayesian model and temporal difference learning algorithms that have been proposed as models of human reinforcement learning. In two experiments we test several predictions of this model, providing behavioral evidence that humans learn and exploit structured inductive knowledge to make predictions about novel actions. We suggest a new interpretation of dopaminergic responses to novelty in light of this model. Keywords: reinforcement learning, Bayesian inference, exploration, exploitation

The authors investigated people's ability to restructure their knowledge when additional information about a categorization task is revealed. In 2 experiments, people first learned to rely on a fairly accurate (but imperfect) predictor. At various points in training, a complex relationship between 2 other predictors was revealed in a schematic diagram that could support perfect performance. In Experiment 1, people adopted the complex strategy when it was revealed at the outset but were unable to restructure their knowledge after the expedient predictor had been learned. In Experiment 2, expedient knowledge persisted even with an adaptive display. The persistence of expedient knowledge is explained by associative blocking of potential alternative cues. A 3rd experiment analyzed the strategies people use with and without the diagram. The study confirmed that the diagram, when presented at the outset, significantly alters people's approach to the task. Knowledge restructuring is often observed when people develop new skills, both in the real world and in the laboratory; paradoxically, expertise at these skills in some cases also seems to prevent restructuring of knowledge. Little is known about the processes involved in knowledge restructuring, and our investigation formed

Abstract not found