In the experiments of comparative visual search reported here, each half of a display contains simple geometrical objects of three different colors and forms. The two hemifields are identical except for one mismatch either in color or form. The subject's task is to find this difference. Eye-movement recording yields insight into the interaction of mental processes involved in the completion of this demanding task. We present a hierarchical model of comparative visual search and its implementation as a computer simulation. The evaluation of simulation data shows that this Three-Level Model is able to explain about 9 8 % of the empirical data collected in six different experiments.

Category learning is an essential cognitive mechanism for making sense of the world. Many existing computational category learning models focus on categories that can be represented as feature vectors, and yet a substantial part of the categories we encounter have members with inner structure and inner relationships. We present a novel computational model that perceives and learns structured concepts from physical scenes. The perception and learning processes happen simultaneously and interact with each other. We apply the model to a set of physical categorization tasks and promote specific types of comparisons by manipulating presentation order of examples. We find that these manipulations affect the algorithm similarly to human participants that worked on the same task. Both benefit from juxtaposing examples of different categories – especially ones that are similar to each other. When juxtaposing examples from the same category they do better if the examples are dissimilar to each other.