Reaction time as an indicator of instance typicality in conceptual spaces

In typical categorization tasks, humans are presented with a sequence of instances and report whether each instance is a member of a given category or not. In the current study, we examine the relationship between the reaction times (RTs) of human participants and the position of the instance in the conceptual space. Our main hypothesis is that instances closer to the boundary of the two categories, which are harder to be categorized, will require longer cognitive processing, resulting in longer RTs. Human subjects categorized images of novel objects to one of two given categories (represented by images of their prototypes); the selected category, RT and confidence rating for each trial were recorded. For trials with longer RTs people responded with less confidence and were more prone to making errors than for trials with shorter RTs. Moreover, people responded faster to stimuli with high similarity to at least one of the prototypes of the given categories than to stimuli that were distant from both prototypes, and hence closer to the boundary of the two categories, confirming our main hypothesis. � 2018 CEUR-WS. All rights reserved.