Analysis of categorical response data: use logistic regression rather than endpoint-difference scores or discriminant analysis.

Example of a typical second-language (L2) speech perception experiment: Synthetic vowel stimuli from a two-dimensional grid of points in which acoustic properties vary systematically in duration and spectral properties are classified as English /i/ or /I/ by L2-English listeners. In a number of studies, the data from such experiments have been analyzed using endpoint-difference scores or discriminant analysis. The current letter describes theoretical problems inherent in the first procedure in general, and in the application of the second procedure to data of this type in particular. Logistic regression is proposed as an alternative, which does not suffer from these problems.