Pavlovian backward conditioned inhibition in humans: summation and retardation tests

Alcohol cues impair learning inhibitory signals in beer drinkers

BACKGROUND

Models of drug addiction emphasize the reciprocal influence of incentive-motivational properties of drug-related cues and poor impulse control resulting in drug use. Recent studies have shown that alcohol-related cues can impair response inhibition. What is unknown is whether these cues also disrupt learning of inhibitory associations.

METHODS

Participants performed a conditioned inhibition (CI) task and were required to learn that a neutral image was a conditioned inhibitor when presented in the context of either an alcohol image intended to draw their attention away from the to-be-trained inhibitor, or a control condition in which the alcohol image was absent. After training, subjects in each condition rated the likelihood that the neutral image would signal the outcome. Eye tracking was used to verify that attention to the neutral image was in fact reduced when the alcohol image was present.

RESULTS

Compared with controls those trained in the alcohol image condition reported a greater likelihood that the presence of the inhibitor would be followed by the outcome and thus were less able to acquire CI. Measures of eye tracking verified that attention to the alcohol cue was associated with this maladaptive behavior.

CONCLUSIONS

When alcohol cues are present, there is a reduced ability to learn that such information is irrelevant to an outcome, and this impairs ones' ability to inhibit perseveration of a response. This has implications for persistence of a drinking episode.

Explaining compound generalization in associative and causal learning through rational principles of dimensional generalization

How do we apply learning from one situation to a similar, but not identical, situation? The principles governing the extent to which animals and humans generalize what they have learned about certain stimuli to novel compounds containing those stimuli vary depending on a number of factors. Perhaps the best studied among these factors is the type of stimuli used to generate compounds. One prominent hypothesis is that different generalization principles apply depending on whether the stimuli in a compound are similar or dissimilar to each other. However, the results of many experiments cannot be explained by this hypothesis. Here, we propose a rational Bayesian theory of compound generalization that uses the notion of consequential regions, first developed in the context of rational theories of multidimensional generalization, to explain the effects of stimulus factors on compound generalization. The model explains a large number of results from the compound generalization literature, including the influence of stimulus modality and spatial contiguity on the summation effect, the lack of influence of stimulus factors on summation with a recovered inhibitor, the effect of spatial position of stimuli on the blocking effect, the asymmetrical generalization decrement in overshadowing and external inhibition, and the conditions leading to a reliable external inhibition effect. By integrating rational theories of compound and dimensional generalization, our model provides the first comprehensive computational account of the effects of stimulus factors on compound generalization, including spatial and temporal contiguity between components, which have posed long-standing problems for rational theories of associative and causal learning.

Are Preventive and Generative Causal Reasoning Symmetrical? Extinction and Competition

We tested whether preventive and generative reasoning processes are symmetrical by keeping the training and testing of preventive (inhibitory) and generative (excitatory) causal cues as similar as possible. In Experiment 1, we extinguished excitors and inhibitors in a blocking design, in which each extinguished cause was presented in compound with a novel cause, with the same outcome occurring following the compound and following the novel cause alone. With this novel extinction procedure, the inhibitory cues seemed more likely to lose their properties than the excitatory cues. In Experiment 2, we investigated blocking of excitatory and inhibitory causes and found similar blocking effects. Taken together, these results suggest that acquisition of excitation and inhibition is similar, but that inhibition is more liable to extinguish with our extinction procedure. In addition, we used a variable outcome, and this enabled us to test the predictions of an inferential reasoning account about what happens when the outcome level is at its minimum or maximum (De Houwer, Beckers, & Glautier, 2002). We discuss the predictions of this inferential account, Rescorla and Wagner's (1972) model, and a connectionist model—the auto-associator.

An instance theory of associative learning

We present and test an instance model of associative learning. The model, Minerva-AL, treats associative learning as cued recall. Memory preserves the events of individual trials in separate traces. A probe presented to memory contacts all traces in parallel and retrieves a weighted sum of the traces, a structure called the echo. Learning of a cue-outcome relationship is measured by the cue's ability to retrieve a target outcome. The theory predicts a number of associative learning phenomena, including acquisition, extinction, reacquisition, conditioned inhibition, external inhibition, latent inhibition, discrimination, generalization, blocking, overshadowing, overexpectation, superconditioning, recovery from blocking, recovery from overshadowing, recovery from overexpectation, backward blocking, backward conditioned inhibition, and second-order retrospective revaluation. We argue that associative learning is consistent with an instance-based approach to learning and memory.

Positive and negative mediation as a function of whether the absent cue was previously associated with the outcome

After presenting two cues, A and B, together, later pairings of one of the cues alone with an outcome can generate changes in the associative value of the absent cue. These changes can be in the same direction as the present cue (i.e., positive mediation) or in the opposite direction to the present cue (i.e., negative mediation). We found both mediational effects in a human contingency task. In addition, we found that the direction of the change was determined by the existence of a prior association between the absent cue and the outcome. When a prior association exists, the absent cue tends to change its value in the opposite direction to the present cue, whereas when there is no prior association, the absent cue tends to change its value in the same direction as the present cue. Recent associative models (Stout & Miller, 2007) can explain our results.