Recall as a function of number of classificatory categories.

Some psychologists are interested in the organism's processing of information—how it is received or selected, organized, stored, made available when needed. Categories are important in the processing of information because they establish equivalences in our Heraclitian world, making it possible for the organism to profit by experience and react at a better-thanchance level with the environment (3, 8, 12). It seems evident that the process of categorizing is itself one determinant of which previous experiences are brought to bear on subsequent occasions. That the use of a particular category influences the content of the information that is recalled has been demonstrated in many ways (1, 4). However, the influences of formal characteristics of categories, such as how many there are, their distinctness, exclusiveness, "ecological validity," generality, etc., have been studied very little. The problem of the present study" is the apparently simple one of how mere number of categories affects the amount of information that can be recalled. A further problem is how such effects can be explained in terms of more molecular psychological concepts concerning cognitive processes.