Effect of proximity of elements on the feature-positive effect.
Push the 'no-reinforcement' parts of a stimulus together to help learners spot when to hold back.
01Research in Context
What this study did
Sainsbury (1971) worked with pigeons to see how close or far stimulus parts should sit. The birds pecked at screens where tiny shapes either touched or had gaps between them.
Some trials were feature-positive: one shape meant food was coming. Others were feature-negative: the same shape meant no food. The team tracked how often birds picked the right choice.
What they found
When the shapes were pushed together, pigeons got better at the feature-negative task. They learned faster which display meant 'no food'.
The same squeeze did not help the feature-positive task. Birds already did well when the shape signaled food, no matter the spacing.
How this fits with other research
Stevenson (1966) showed that tighter test spacing flattens generalization curves. Sainsbury (1971) adds that tight spacing can also sharpen discrimination, but only when the cue tells the bird to hold back.
Schwartz (1975) moved the cue to different spots on the response key and saw positive contrast rise. Together these papers say: where and how close stimuli sit changes what the animal learns.
Kirkpatrick-Steger et al. (1996) scrambled object parts and watched recognition drop. Their result lines up with Sainsbury (1971): break the usual layout and performance suffers.
Why it matters
If you run discrimination lessons, pack the 'no-go' cues close together. Keep the 'go' cues spread if you like, because spacing does not hurt those. This small layout tweak can cut errors in half when learners must withhold a response.
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02At a glance
03Original abstract
Eight groups of pigeons were trained to discriminate between two stimulus displays that could be differentiated only by a single distinctive feature on one of the displays. For half of the pigeons, responses to displays containing the distinctive feature were reinforced (feature-positive), and for the remaining pigeons responses to displays without the distinctive feature were reinforced (feature-negative). The pigeons were further grouped so that half were presented displays in which the distinctive feature was in close proximity to other features (compact displays) and half were presented displays in which the features were not close together (distributed displays). Pigeons in the feature-positive groups localized responses on the distinctive feature of the displays and seldom responded to displays without the distinctive feature. Pigeons in the distributed feature-negative groups localized responses on features common to the two displays and did not learn the discrimination. Compacting the displays facilitated discrimination performance for the subjects in the feature-negative condition. Tests carried out in extinction indicated that responding in the compact feature-negative group was largely controlled by pattern rather than by the individual elements on the display.
Journal of the experimental analysis of behavior, 1971 · doi:10.1901/jeab.1971.16-315