Conditional discrimination learning in the pigeon.
Compound color-form cues can teach conditional discriminations, but form may outshine color unless you program reinforcement to notice both.
01Research in Context
What this study did
Researchers taught pigeons to peck only when a color-form pair matched a sample. For example, red-circle plus green-triangle meant peck left, while red-triangle plus green-circle meant peck right.
They then dimmed or brightened the colors to see if the birds would still choose correctly.
What they found
The pigeons kept choosing correctly even when colors changed intensity. Shape cues controlled their choices more than color cues.
This shows compound cues can work, but one part may steal control.
How this fits with other research
Bennett et al. (1973) seems to disagree. They saw worse matching when pigeons got compound samples instead of single cues. The gap is about task type: G et al. used conditional discrimination while S et al. used matching-to-sample. Different rules, different outcomes.
Catania (1973) and Wilkie (1973) build on the 1969 result. C showed that redundant compounds speed up learning, and M showed you must reinforce both dimensions or the bird will ignore one.
Later work like Paul et al. (1987) added that daily alternation of problems helps pigeons lock in conditional control.
Why it matters
When you set up conditional discrimination lessons, know that compound cues can help, but one cue may dominate. Check which dimension the learner actually uses. If you want control by both color and shape, make sure reinforcement depends on both, and switch tasks often. Start with redundant cues, then fade to the one you care about most.
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02At a glance
03Original abstract
Four pigeons received conditional discrimination training in which reinforcement contingencies were related to specific combinations of color and form, but were unrelated to either color or form considered separately. During discrete-trial training, each response in the presence of two of four color-form displays produced reinforcement and terminated the trial; responding to the other two displays was never reinforced, and each such response prolonged the particular trial on which it occurred. Subsequently, the subjects received multiple-schedule training in which responding to either of the displays previously associated with reinforcement was now reinforced on a variable-interval schedule, and extinction was the schedule again correlated with the other two displays. After differential responding to the stimuli was clearly evident, intensity of the combination displays was changed in subsequent training sessions. Complex stimulus control was generally maintained across variation in intensity, although there were temporary disruptions in performance associated with onset of some of the intensity changes. Finally, a component-stimulus test revealed considerably more responding to the forms than to the colors.
Journal of the experimental analysis of behavior, 1969 · doi:10.1901/jeab.1969.12-119