Perceptual Categorization: Connectionist Modelling and Decision Rules

Although it is currently popular to model human associative learning using connectionist networks, the mechanism by which their output activations are converted to probabilities of response has received relatively little attention. Several possible models of this decision process are considered here, including a simple ratio rule, a simple difference rule, their exponential versions, and a winner-take-all network. Two categorization experiments that attempt to dissociate these models are reported. Analogues of the experiments were presented to a single-layer, feed-forward, delta-rule network. Only the exponential ratio rule and the winner-take-all architecture, acting on the networks' output activations that corresponded to responses available on test, were capable of fully predicting the mean response results. In addition, unlike the exponential ratio rule, the winner-take-all model has the potential to predict latencies. Further studies will be required to determine whether latencies produced under more stringent conditions conform to the model's predictions.     

“To hope was to expect”: The impact of perspective taking and forecast type on wishful thinking

When forecasting future outcomes, people tend to believe that the outcomes they want to happen are also likely to happen. Despite numerous attempts, few systematic factors have been identified that consistently and robustly reduce wishful thinking (WT) effects. Using elections and sporting event outcomes as contexts, three experiments examined whether taking the perspective of a political rival or opposing fan reduced WT effects. We also examined whether making deliberative (vs. intuitive-based) forecasts was associated with lower WT effects. Online adult samples of U.S. citizens from Mechanical Turk and U.S. college students provided their preferences and forecasts for the U.S. presidential election (Experiments 1 and 2) and a sports competition outcome (Experiment 3). Critically, some participants received perspective taking prompts immediately before providing forecasts. First, results revealed reductions in WT effects when participants engaged in perspective taking. Interestingly, this effect only emerged when intuitive-based forecasts were made first (Experiment 3). Second, intuitive-based forecasts revealed stronger evidence of WT effects. Finally, we found that perspective taking and forming forecasts deliberately promoted a shift in focus away from preferences and toward a consideration of the relative strengths and weaknesses of the entities (i.e., candidates and teams). Theoretical implications for understanding WT effects and applied implications for developing interventions are discussed.     

Context specificity of latent inhibition in taste aversion learning

In three experiments rats were given injections of LiCl after consuming distinctively flavoured water. The rats developed an aversion to the flavour and in all experiments the magnitude of the aversion was found to be reduced in subjects that had received pre-exposure to the flavour without aversive consequences. Experiment 1 demonstrated this pre-exposure effect to be a case of latent inhibition. The remaining experiments investigated the effects of pre-exposing the flavour in a context different from that used for conditioning. It was found (Experiment 2) diat latent inhibition transferred perfectly when the context change consisted of a move from one home cage to another. Context specificity of latent inhibition was found (Experiment 3) only when the subjects were given daily sessions in die experimental contexts, these being cages different from the home cage.