Purchase this article with an account.
Casimir Ludwig, Rhys Davies; Estimating the growth of discriminative information guiding perceptual decisions. Journal of Vision 2011;11(11):1171. doi: 10.1167/11.11.1171.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Perceptual decision-making is thought to involve a gradual accrual of noisy sensory evidence. Temporal integration of the evidence reduces the relative contribution of dynamic internal noise to the decision variable, thereby boosting its signal-to-noise ratio. We aimed to estimate the discriminative quality of the internal representations guiding perceptual decisions over time, using a novel combination of external noise and signal-to-respond methods. Observers performed orientation discrimination of patterns presented in external noise. We varied the contrast of the patterns and the delay at which observers were forced to signal their decision. Each test stimulus (patterns and noise sample) was presented twice. Analysis of performance at a single contrast level showed that accuracy conformed to a standard ‘speed-accuracy’ curve: discrimination accuracy improved over time according to an exponential growth function. However, observer model analysis of discrimination accuracy and response consistency to two passes of the same stimulus, suggested very little growth in discriminative information. The improvement in performance over time predominantly reflected a decreasing proportion of non-visual, or purely random, decisions. The standard speed-accuracy growth curve collected in signal-to-respond paradigms is therefore not necessarily indicative of an improvement in discriminative quality of the internal representations guiding decision-making. The relative constancy of the discriminative information over time suggests that the dominant source of internal noise limiting performance is static and cannot be compensated for by prolonged evidence integration.
This PDF is available to Subscribers Only