A difference that is not a difference: Reply to Vanderploeg and Logan.

Replies to Vanderploeg and Logan's comment on Russell and Levy's (1987) article. We used statistics to support the contention that differences in the Revised Category Test (RCAT), which was introduced by Russell and Levy, did not change what the original Category Test (CAT) was measuring. Rather than being a substitute for the test–retest criterion method, rescoring items from the CAT eliminated much of the variance introduced by retesting. Two new forms of criterion testing that reduce error variance are suggested. Multiplying the RCAT raw score by 2.2 provides scores that are close to those derived from the CAT. Finally, evidence is presented that, for the subject, the primary difficulty in the CAT is making conceptual rather than perceptual shifts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)