We investigated whether the presence of exception items can impede effects of category compression (within-category items appearing more similar) in classification learning. We hypothesized that the distinct representations afforded to exceptions may cause the target category to appear less cohesive, thereby reducing the likelihood of compression occurring. Across two experiments, participants engaged in classification learning without exceptions, with an easy exception, or with a difficult exception. Pairwise similarity ratings for all items were collected before and after learning to index compression. Results from Experiment 1 suggest that difficult exceptions can impede compression for the contrast category when situated within its cluster, while results from Experiment 2 suggest that both kinds of exceptions can impair compression of standard items in a target category relative to the No Exception control. We also observed surprising evidence of a novel between-category compression effect that was observed with the category structure developed for these experiments.

The mnemonic benefits of animate (e.g., Tiger) over inanimate (e.g., Table) stimuli have been demonstrated across several different memory paradigms. Given the ubiquity of inanimate, computer-generated voices we investigated if the animacy of a presentation source confers mnemonic benefits. We asked: is information delivered by a human voice better remembered than information presented by a computer-generated voice? Word-lists were presented auditorily by either a human or a computer-generated voice and memory was measured using a free recall assessment. In Experiment 1, words presented in a human voice were better remembered than words presented in a computer voice. Experiment 2 demonstrated that beliefs about the animacy of a computer-generated voice were not sufficient for any benefits to accrue, suggesting a possible boundary condition for the effect. Both experiments replicated the mnemonic benefits of animate words and demonstrated further extensions of the effect to spoken word presentation.