On-line choice and the representation of serially structured stimuli.

Three groups of pigeons were trained to discriminate between a target temporal sequence, consisting of red, green, and blue, and distractor sequences consisting of all other combinations of these three colors presented on a pecking key. Response alternatives were provided during the course of the trial (on-line decisions) as well as the end of the trial (postsequence decisions). Different temporal phrasing patterns emphasized the first stimulus in the sequence, the final stimulus, or all stimuli equally. The phrasing pattern did not affect the speed of acquisition, but groups receiving emphasized stimuli relied more heavily on those stimuli than on the other stimuli for their discriminations. The patterns of both on-line choices during the sequence and terminal choices following the sequence were consistent with the use of hierarchical representations and inconsistent with a simple item-by-item prospective discrimination scheme.