The limits of deliberation in a perceptual decision task.

While it is commonly assumed that decisions taken slowly result in superior outcomes, is it possible that optimal decision making does not always require sacrificing speed? For odor categorization decisions, it was previously shown that rats use <300 ms regardless of difficulty, but these findings could be interpreted as a tradeoff of accuracy for speed. Here, by systematically manipulating the task contingencies, we demonstrate that this is the maximum time over which sampling time can improve accuracy. Furthermore, we show that decision accuracy increases at no temporal cost when rats can better anticipate either the identity of stimuli or the required timing of responses. These experiments suggest that uncertainty in odor category decisions arises from noise sources that fluctuate slowly from trial-to-trial rather than rapidly within trials and that category decisions in other species and modalities might likewise be optimally served by rapid choices.