Dittrich, W. H., Lea, S. E. G., Barrett, J., & Gurr, P. R. (1998).
Categorization of natural movements by pigeons: Visual concept discrimination and biological motion.
Journal of the Experimental Analysis of Behavior,
70, 281-299.
In three experiments, pigeons were exposed
to a discriminated autoshaping procedure in which categories of
moving stimuli, presented on videotape, were differentially
associated with reinforcement. All stimuli depicted pigeons
making defined responses. In Experiment 1, one category consisted
of several different scenes of pecking and the other consisted of
scenes of walking, flying, head movements, or standing still.
Four of the 4 birds for which pecking scenes were positive stimuli
discriminated successfully, whereas only 1 of the 4 for which
pecking was the negative category did so. In the pecking-positive
group, there were differences between the pecking rates in the
presence of the four negative actions, and these differences were
consistent across subjects. In Experiment 2, only the categories
of walking and pecking were used; some but not all birds learned
this discrimination, whichever category was positive, and these
birds showed some transfer to new stimuli in which the same
movements were represented only by a small number of point lights
(Johansson's "biological motion" displays). In Experiment 3,
discriminations between pecking and walking movement categories
using point-light displays were trained. Four of the 8 birds
discriminated successfully, but transfer to fully detailed
displays could not be demonstrated. Pseudoconcept control groups,
in which scenes from the same categories of motion were used in
both the positive and negative stimulus sets, were used in
Experiments 1 and 3. None of the 8 pigeons trained under these
conditions showed discriminative responding. The results suggest
that pigeons can respond differentially to moving stimuli on the
basis of movement cues alone.
Key words: concept discrimination, biological
motion, motion features, natural categories, video images, key
peck, pigeons