Performance of rats on a discrimination operant alley task discriminated

An automated discriminated operant alley apparatus is described. Data from four rat strains indicate that the light-dark choice is learned by both pigmented and albino rats. The task requires a minimum of experimenter time and allows initial acquisition to be recorded without the interference of a shaping procedure.     

Significant category clustering in free recall

Frender and Doubilet suggest that Bousfield's ratio of repetitions (RR) is the best measure of clustering in free recall presently available. Conditioning only on the number of words recalled, they determine the mean ofRR in the absence of clustering. In this note the null variance ofRR is presented. This permits development of conservative significance tests based on the Cramér inequality.