DIRECTIONAL SELECTION OF RESPONSE NUMEROSITY: AN EXPLORATORY STUDY

Abstract

The experiment examined how pigeons differentiate response patterns along the dimension of number. Seven pigeons received food after pecking the left key at least N times and then switching to the right key (Mechner’s Fixed Consecutive Number schedule). Parameter N was set according to a percentile schedule, which is a form of automatic shaping. Our aim was twofold: on the empirical side to determine how run length on the left key would evolve under this shaping procedure and how it would change during a subsequent extinction phase; and on the theoretical side to compare the data with the predictions of a theoretical model of response differentiation. Results showed that during shaping, run length on the left key increased and then, for some pigeons, it stabilized, whereas for others pigeons it remained variable. Some pigeons ceased to respond when average run length reached a highvalue. There were substantial within-session trends in run length. In extinction, before the pigeons ceased to respond altogether, they emitted the same distribution of run lengths as during the last sessions of shaping with the exception, in some birds, of a large number of runs of length zero. These results are interpreted at the light of the theoretical model of numerosity differentiation.Keywords: Mathematical Model, Response Numerosity, Percentile Schedule, Shaping, Pigeon