The psychophysics of decision making in a two-direction random dot motion target selection task
Random dot kinematograms are used in visual psychophysics with the two-alternative forced-choice paradigm to study the process of simple perceptual decisions. Mathematical models of this process assume that stochastic motion evidence for the two alternative choices is encoded in the brain, and that the difference in evidence is accumulated towards a decision bound. However, no study to date has tested this assumption using stimuli with different levels of mutually opposing evidence in both directions. This thesis presents the results of two experiments using two novel stimuli with opposing coherent motion evidence. Over a variety of competing evidence combinations, subject performance was based on the net difference in the opposing signals. Furthermore, task performance was similar with both types of stimuli. These results support a decision model based on the accumulation of net evidence, and suggest that the decision process is capable of integrating motion evidence from a wide range of directions to obtain a global percept of motion.
Decision making Psychophysics Sensorimotor integration Random dot motion Two alternative forced choice