Reaction times to weak test lights

Maloney and Wandell [Vision Res. 24, 633-640 (1984)] describe a model of the response of a single visual channel to weak test lights. The initial channel response is a linearly filtered version of the stimulus. The filter output is randomly sampled over time. Each time a sample occurs there is some probability--increasing with the magnitude of the sampled response--that a discrete detection event is generated. Maloney and Wandell derive the statistics of the detection events. In this paper we test the hypothesis that the reaction time responses to the presence of a weak test light are initiated at the first detection event. This permits us to extend the application of the model to lights that are slightly above threshold, but still within the linear operating range of the visual system. We test a parameter-free prediction of the model proposed by maloney and Wandell for lights detected by this statistic. The data are in agreement with the prediction.