Comments on Shimp's (1983) double dissociation between knowledge and tacit knowledge.

Shimp (1983) found in five pigeons "double dissociation" between the distribution of pairs of long and short reinforced interresponse times and "self-reports," obtained by symbolic matching to sample, concerning these interresponse times. This result can be explained by assuming that the birds used a fixed temporal interval as matching criterion, independently of which pattern of interresponse times was reinforced.