An emerging view in cognitive psychology is that the determination of similarity involves a comparison of structured representations. O n this view, s o m e differences are related to the commonalities of a pair {alignable differences) and others are unrelated to the commonalities of a pair {nonalignable differences). Previous evidence suggests that pairs of similar items have more commonalities and alignable differences than do pairs of dissimilar items. Structural alignment further predicts that alignable differences should be easier to findthan nonalignable differences. T a k e n together, these assertions lead to the counterintuitive prediction that it should be easier to find differences for similar pairs than for dissimilar pairs. This prediction is tested in two studies in which subjects are asked to list differences for as m a n y word pairs as possible in a short period of time. In both studies, more differences are listed for similar pairs than for dissimilar pairs. Further, similar and dissimilar pairs differ in the number of alignable differences listed for them, but not in the number of nonalignable differences listed for them. These studies provide additional support for the structural alignment view of similarity.

Tversky demonstrated that the similarity of two objects increases with their commonalities and decreases with their differences. W e believe that determining commonalities and differences is a complex task. Using analogical mapping as a guide, we propose the process of frame-alignment which can be employed to find the commonalities and differences of structured representations. W e then test the predictions of this approach by asking subjects to list the commonalities and differences of word pairs that vary in their degrees of similarity. The results of this study support the predictions of the frame-alignment view.

We propose that carrying out a similarity comparison of two objects or scenes requires that their components be aligned in a manner akin to analogical mapping. W e present an experiment which supports this claim and then examine a computer simulation of these results which is consistent with the idea that a process of mapping and alignment occurs during similarity judgments.

Two different views of the organization of verbs in the mental lexicon have been formulated in recent years: the matrix view and the cluster view. The matrix view suggests that a verb shares as many features with verbs from other clusters as it shares with verbs from its own cluster. Thus, instead of being organized, like concrete nouns into well-defined hierarchies, verbs in the mental lexicon form a matrix like structure. While admitting differences between the organization of verb and noun lexicons, the cluster view claims that verbs form hierarchically organized clusters that resemble noun hierarchies in many ways. We report one study that extends research on similarity of nouns to verbs in order to shed light on these accounts. Subjects were presented with pairs of verbs and asked to list their commonalities or differences. The obtained patterns of commonalities, alignable and nonalignable differences are similar to the patterns obtained for hierarchies of nouns and are consistent with the cluster view of verb organization.

It is widely acknowledged that categories have many functions, but few studies have actually addressed the impact of these functions on the way categories are learned. For instance, many categorization experiments predominantly rely on classification-based incremental learning. The problem with this approach is that it implicitly assumes that the function of categorization is separable from the way that categories are learned. In this study, we examined the relation between learning and the subsequent use of categories by contrasting three types of category-learning methods — inference-based, classification-based, and a combination of these methods. The results of the experiment indicate that there is an intricate relationship between category-learning and subsequent use of the category. The results further suggest that different processing modes may have been adopted by subjects in the different learning conditions.