Figure 2.

Preexperimental stimulus set ratings. A, An independent group of subjects rated all possible picture stimuli as accurately belonging to their intended category (p < 0.001, one-sample t tests). B, Preexperimental ratings from experimental subjects confirmed that familiar odors were accurately rated as fruity or floral. *p < 0.01 (one-sample t tests). Importantly, before learning, the novel odors were not consistently rated as belonging to either category (p > 0.26, one-sample t tests). Data are mean ± SEM.