Date of Award


Document Type


Degree Name

Master of Arts in General Experimental Psychology



First Reader/Committee Chair

Clapper, John


This experiment investigated the processes underlying similarity-based free categorization. Of particular interest was how temporal distance between similar objects affects the likelihood that people will put them into the same novel category. Participants engaged in a free categorization task referred to as binomial labeling. This task required participants to generate a two-part label (A1, B1, C1, etc.) indicating family (superordinate) and species (subordinate) levels of categorization for each object in a visual display. Participants were shown the objects one at a time in a sequential presentation; after labeling each object, they were asked to describe the similarity between that object and previous objects by selecting one of five choices from a drop down menu. Our main prediction was that temporal distance should affect categorization, specifically, that people should be less likely to give two identical objects the same category label the farther apart they are shown in the display. The primary question being addressed in this study was whether the effects of distance are due to a decreased likelihood of remembering the first object when labeling the second (what we refer to as a stage 1 or sampling effect) or to factors during the actual comparison itself (a stage 2 or decision effect)? Our results showed a significant effect of distance on both the likelihood of giving identical objects the same label as well as on the likelihood of mentioning the first object when labeling the second object in an identical pair. Specifically, as the distance between two identical objects increased, the likelihood of giving them the same label, as well as mentioning their similarity, both decreased. Importantly, the decreased probability of giving the second object the same label seemed entirely due to the decreased probability of remembering (sampling) the first object, as indicated by the menu responses. These results provide strong support for the idea that the effect of temporal distance on free categorization is mainly due to stage 1 factors, specifically to its effect on the availability of the first instance in memory when labeling the second. No strong evidence was found in this experiment supporting a separate distance effect at the comparison-decision stage (i.e., stage 2).