Acquisition under Mixed-Delay and Multiple-Delay Matching-to-Sample

The acquisition of delayed matching to sample in two groups of pigeons was examined when three delay values (2, 4, and 6 sec.) were mixed across trials and when each of the three delay values was correlated with one of three standard stimuli (i.e., multiple delays). Extended training resulted in the acquisition of matching by all multiple-delay Ss, while only one of three mixed-delay Ss showed comparable performance. The one S which acquired matching under the mixed condition emitted standard, specific, delay behaviors. The results suggest that acquisition of delayed matching may be highly dependent upon the availability of some source of delay-stimuli that are consistently correlated with standard stimuli.