DELAYED MATCHING IN PIGEONS - CAN APPARENT MEMORY LOSS BE ATTRIBUTED TO THE DELAY OF REINFORCEMENT OF SAMPLE-ORIENTING BEHAVIOR

In earlier research using constant-delay matching with pigeons, there is evidence that delay of reinforcement of sample-orienting behavior m ay contribute to the decline in matching accuracy with increasing dela y between sample and comparison stimuli. In the present research using this procedure, we found that a significant decline in matching accur acy between the first and second session can occur when delays are rel atively long. This effect cannot be accounted for in terms of either a dditional memory loss or surprise (generalization decrement) associate d with the increase in delay. Furthermore, the decline in matching acc uracy occurred regardless of whether the delay was inserted between sa mples and comparisons (where it would be expected to affect the use of sample memory in making the comparison choice response) or between co mparisons and reinforcement (where it would not be expected to affect the use of sample memory in making the comparison choice response). Th us, the decrease in matching accuracy between Session I and 2 followin g an increase in delay appears to be unrelated to sample memory at the time of choice. Instead, the results suggest that delay of reinforcem ent of sample-orienting behavior may play an important role in the neg ative slope of the retention functions obtained when constant-or mixed -delay matching procedures are used to assess animal memory. (C) 1998 Elsevier Science B.V. All rights reserved.