RT Journal Article SR Electronic T1 The Cost of Accumulating Evidence in Perceptual Decision Making JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 3612 OP 3628 DO 10.1523/JNEUROSCI.4010-11.2012 VO 32 IS 11 A1 Drugowitsch, Jan A1 Moreno-Bote, Rubén A1 Churchland, Anne K. A1 Shadlen, Michael N. A1 Pouget, Alexandre YR 2012 UL http://www.jneurosci.org/content/32/11/3612.abstract AB Decision making often involves the accumulation of information over time, but acquiring information typically comes at a cost. Little is known about the cost incurred by animals and humans for acquiring additional information from sensory variables due, for instance, to attentional efforts. Through a novel integration of diffusion models and dynamic programming, we were able to estimate the cost of making additional observations per unit of time from two monkeys and six humans in a reaction time (RT) random-dot motion discrimination task. Surprisingly, we find that the cost is neither zero nor constant over time, but for the animals and humans features a brief period in which it is constant but increases thereafter. In addition, we show that our theory accurately matches the observed reaction time distributions for each stimulus condition, the time-dependent choice accuracy both conditional on stimulus strength and independent of it, and choice accuracy and mean reaction times as a function of stimulus strength. The theory also correctly predicts that urgency signals in the brain should be independent of the difficulty, or stimulus strength, at each trial.