A role for spatial proximity in feature-positive discriminations using spatial search tasks in rats and humans

Winstead, Sara Rene

Item

A role for spatial proximity in feature-positive discriminations using spatial search tasks in rats and humans

Winstead, Sara Rene

Date

2025-08-06

Abstract

Feature-positive discriminations involve reinforcement of a feature-target compound (XA+) and nonreinforcement of the target alone (A-). The temporal proximity between the feature and target have been frequently studied. When X is less temporally proximal to A and reinforcement (i.e., serial; X→ A+, A-), occasion setting typically occurs. Whereas when X is more temporally proximal to A and reinforcement (i.e., simultaneous; XA+, A-), direct control by X typically occurs. These effects suggest that the temporal proximity of cues influence their salience or noticeability. Salience can also be affected by physical intensity, (i.e., brightness, loudness, size), with a more physically intense A leading to occasion setting, and a less intense A resulting in direct control. Manipulating spatial proximity can also influence salience but hasn’t been looked at directly in feature-positive discriminations. The current experiments utilized a spatial feature-positive discrimination, where one response is correct in the presence of X and A (e.g., left cup), but another response (e.g., right cup) is correct in the presence of A alone. In both experiments, the target and reinforcer was either more (near) or less proximal (far) to the feature. We hypothesized that when the feature and target are near, that occasion setting-like behavior would occur and when far, direct control, or failure to acquire the task would occur. In Experiment 1, rats did not learn the discrimination in either group, due to other cues overshadowing the target landmark cue. In Experiment 2, humans underwent a similar procedure with both Near and Far groups, with effect of anxiety (Non-anxious, Anxious) on feature-positive learning also being evaluated. Results revealed that all participants were more anxious after the task and did not learn about both XA and A trials. However, during feature extinction testing, there was a reduction in responding to the extinguished X, but not to XA in the Non-anxious Near, Anxious Near, and Anxious Far groups, which is consistent with occasion setting. No evidence of occasion setting occurred in the Non-anxious Far group. Additional research is needed to continue to explore the effects of anxiety and spatial proximity on feature-positive learning.