Adventitious control by the location of comparison stimuli in conditional discriminations.
Changing where choices appear does not remove position cues; learners just stick the new pictures onto the same lucky spot.
01Research in Context
What this study did
Pigeons pecked keys in a two-choice conditional discrimination. The comparison pictures moved around, but one key spot always paid off.
Researchers tracked hits, false alarms, and preference to see if shifting locations could wipe out position cues.
What they found
Key position stayed in charge even when pictures jumped to new spots. Birds simply learned new compounds: picture-plus-place.
Signal-detection plots showed separate curves for learning and for later disruption, proving two layers of control.
How this fits with other research
Meltzer (1983) showed that putting the blurry cue on the non-paying key sharpened control. Davison (1992) adds that moving the whole array does not erase the payoff key's pull; it just lets the bird glue new colors to the same lucky spot.
Davison (2018) seems to clash: delaying reward after the peck weakened location control but not color control. The gap closes when you see the methods: Davison inserted a 3-s pause after reinforcement, breaking the immediate place-reward link, while M kept reward tied to the key. Timing, not place, explains the difference.
Badia et al. (1972) already proved that with clear differential reinforcement, pigeons lock onto auditory location in one or two sessions. M extends that lesson to visual arrays: once a spot wins, it keeps winning.
Why it matters
For your next conditional-discrimination program, do not assume rotating choices will kill side biases. Check which position has a history of hits; that spot may still rule the learner's choices. If you need clean stimulus control, separate the reward from the key location or insert a brief delay, as Davison showed. Track hits and false alarms for a week; the curves will tell you whether the learner is mastering the pictures or just hugging the lucky key.
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Join Free →Map each learner's hit rate by key position; if one side is above 80%, shuffle reward to the other key or add a 2-s delay after reinforcement.
02At a glance
03Original abstract
In a conditional discrimination procedure, samples appeared in a center key, and comparisons appeared in two of four outer keys. The location of comparison keys varied from trial to trial. Separate learning curves for each of the six possible pairs of comparison keys were plotted in a signal-detection space, revealing different patterns of progress on each pair. Also, when learned conditional discriminations were disrupted, pairs of keys differed in their patterns of disruption. Varying the location of comparison stimuli among six different pairs of keys had not eliminated key position as a controlling aspect of the stimuli. The variations simply increased the number of stimulus compounds--key position and experimental stimuli--that the subject learned. Plotting conditional-discrimination learning curves in a signal-detection space reveals relations among hits, false alarms, accuracy, and comparison preference that help to define a subject's progress.
Journal of the experimental analysis of behavior, 1992 · doi:10.1901/jeab.1992.58-173