Gradience - The Modern Definition of Categorical Perception

The Modern Definition of Categorical Perception

This evolved into the contemporary definition of CP, which is no longer peculiar to speech or dependent on the motor theory: CP occurs whenever perceived within-category differences are compressed and/or between-category differences are separated, relative to some baseline of comparison. The baseline might be the actual size of the physical differences involved, or, in the case of learned CP, it might be the perceived similarity or discriminability within and between categories before the categories were learned, compared to after.

The typical learned CP experiment would be the following: A set of stimuli is tested (usually in pairs) for similarity or discriminability. In the case of similarity, Multidimensional scaling might be used to scale the rated pairwise similarity of the set of stimuli. In the case of discriminability, same/different judgments and signal detection analysis might be used to estimate the pairwise discriminability of a set of stimuli. Then the same subjects or a different set are trained, using trial and error and corrective feedback, to sort the stimuli into two or more categories. After the categorization has been learned, similarity or discriminability are tested again, and compared against the untrained data. If there is significant within-category compression and/or between-category separation, this is operationally defined as CP.