A diffusion model analysis of prior probability and spatial attention

Spatial attention and prior probability manipulations have been shown to induce response biases in perceptual decision making behavior. Here, we study the interplay between spatial attention and prior probability manipulations. Participants completed a novel two-alternative forced choice task which simultaneously manipulates spatial attention and prior probability in a factorial design. The task features two cues which prompt the participant to attend to one side of the screen and to expect a given stimulus. A preliminary behavioral analysis showed strong influence of spatial attention and weak influence of prior probability on both RT and accuracy. We fit several variants of the diffusion decision model (DDM) to test which cognitive processes are affected by each manipulation. Preliminary results suggests that the prior probability manipulation affects the starting point parameter, and the attention manipulation the drift rate and non-decision times, in line with earlier literature. The results of this study will set the stage for an fMRI project investigating the neural underpinnings of spatial attention and perceptual expectation.