Keuken, M. 1, 2 , Forstmann, B. U. 1 & Van Maanen, L. 1
1 Cognitive Science Center Amsterdam, University of Amserdam, Amsterdam; The Netherlands
2 MPI for Human Cognitive and Brain Sciences, Leipzig; Germany
A popular paradigm in perceptual decision-making is the random-dot motion task (RDM). In this task participants have to indicate the direction of motion of a cloud of moving dots. Typically, the targets are perpendicular to the central axis, but previous research has shown that the location of targets influences the decision-making process. In Experiment 1 participants performed an RDM task with different target locations. We found that behavior becomes faster and more accurate when the angular distance between the targets increases to 90 degrees but inverts when the distance increases more. There are two possible explanations for this pattern. The first is that motion perception is a two-stage process in which first the movement axis is determined, and then the direction of motion. The second is that information on the movement axis and the motion-direction is integrated over time until a choice is made. In Experiment 2, these explanations were tested by letting participants rate their confidence after each choice. According to the two-stage process, we predicted an increase in confidence ratings for incorrect choices with an increasing angular distance. According to the information integration, the opposite pattern was expected. Results from experiment 2 clearly favor the information integration explanation.