Abstract
If “decision neurons” code for the likelihood of a sensory event by integrating the difference in activity of opposing sensory neurons over time, then the rate at which evidence favoring that event is accumulated can be treated as a measure of response confidence. From this, a simple, quantitative relationship follows; the likelihood of a response being correct should vary linearly with inverse response times. Latency derived receiver operating characteristics (RT-ROCs) were used to convincingly demonstrate that this is the case. Human subjects performed a visual discrimination task at perceptual threshold while the degree of response urgency was manipulated. When accuracy is stressed, inverse response times correlate extremely well with the likelihood of a correct response (r2 > 0.9, p 0.5, p < 0.05), and eventually vanishes. These results provide a method with which to quantify the extent to which a subject is relying on underlying sensory evidence to make a perceptual decision, as opposed to other aspects of decision making, such as response urgency and response bias.