Miyashita, Y., Nakajima, S., & Imada, H. (2000).
Differential outcome effect in the horse.
Journal of the Experimental Analysis of Behavior,
74, 245-253.
Three horses were trained with a discrimination task in which the
color (blue or yellow) of a center panel signaled the correct
(left or right) response (lever press). Reinforcing outcomes for
the two correct color–position combinations (blue–left
and yellow–right) were varied across phases. Discrimination
performance was better when the combinations were differentially
reinforced by two types of food (chopped carrot pieces and
a solid food pellet) than when the combinations were randomly
reinforced by these outcomes or when there was a common
reinforcer for each of the correct combinations. However, the
discrimination performance established by the differential
outcome procedure was still 80% to 90% correct, and an analysis
of two-trial sequences revealed that the stimulus color of the
preceding trial interfered with discrimination performance on a
given trial. Our demonstration of the differential outcome effect
in the horse and its further analysis might contribute to more
efficient control of equine behavior in the laboratory as well as
in horse sports.
Key words: differential outcome effect, proactive interference,
conditional discrimination, lever press, horses