Speed and Accuracy of Static Image Discrimination by Rats

TL;DR

This study shows that rats improve their image discrimination accuracy by taking more time to decide, especially when stimuli are more similar, indicating evidence accumulation in perceptual decision-making.

Contribution

It demonstrates that rats' response times and accuracy are modulated by stimulus similarity, revealing evidence accumulation in static image discrimination tasks.

Findings

Rats respond longer in correct trials than errors.

Discrimination accuracy increases with response latency.

Response times increase with stimulus similarity.

Abstract

When discriminating dynamic noisy sensory signals, human and primate subjects achieve higher accuracy when they take more time to decide, an effect attributed to accumulation of evidence over time to overcome neural noise. We measured the speed and accuracy of twelve freely behaving rats discriminating static, high contrast photographs of real-world objects for water reward in a self-paced task. Response latency was longer in correct trials compared to error trials. Discrimination accuracy increased with response latency over the range of 500-1200ms. We used morphs between previously learned images to vary the image similarity parametrically, and thereby modulate task difficulty from ceiling to chance. Over this range we find that rats take more time before responding in trials with more similar stimuli. We conclude that rats' perceptual decisions improve with time even in the absence of temporal information in the stimulus, and that rats modulate speed in response to discrimination difficulty to balance speed and accuracy.