Machado, A., & Cevik, M. (1997).
The discrimination of relative frequency by pigeons.
Journal of the Experimental Analysis of Behavior,
67, 11-41.
Five experiments addressed the issue of how pigeons learn to
discriminate the relative frequency of stimuli. During a sampling
period, three different stimuli (keylights) were presented
serially, in mixed order, and with different frequencies. During
a choice period, the stimuli were presented simultaneously, and
reinforcement was arranged for choosing the stimulus that was
presented the least number of times during the sample. The
results showed that (a) the overall proportion of correct choices
was always above chance levels; (b) the likelihood of a correct
choice decreased with the serial position of the correct
stimulus, a negative recency effect; (c) when the last three
stimuli of the sample were constrained to be one of each kind,
the negative recency effect decreased but errors became more
likely when the correct stimulus occurred early in the sample, a
negative primacy effect; (d) accurate performance generalized to
new and larger samples; and (e) under some conditions the
probability of a correct choice was independent of the serial
position of the correct stimulus. The serial position curves
suggest that in a least frequent discrimination task, two
processes determine how the least frequent stimulus controls
behavior: a passive decay process (the stimulus loses its
effectiveness with time since its last occurrence), and a
residual salience process (when the stimulus occurs in the first
position it may decay to a higher asymptote than when it occurs
in later positions).
Key words: frequency discrimination, negative recency and
negative primacy effects, temporal integration, generalization,
key peck, pigeon