Background: Anticipation of upcoming events is an adaptive mechanism that ensures quick and accurate perception and action. Consequently, lower Reaction Time (RT) and higher accuracy is found in response to events that can be adequately anticipated. However, events in the world happen with varying degrees of probability depending on context and preceding events. It is therefore of fundamental importance to investigate how knowledge of probability modulates anticipatory processes. Previous studies found effects of stimulus probability on RT and accuracy, but these are only indirect and post-hoc behavioural measures of the anticipatory processes involved. Methods: The present study investigates how knowledge of probability affects real-time anticipatory processes. Behaviour is monitored online by tracking the computer mouse trajectory leading to a required response (mouse-click on Target). The paradigm implements a probability structure that allows the participant to gain knowledge about the relative probability of the occurrence of two alternative events (target occurring at left or right side). Results: Preliminary results indicate that knowledge of probability affects both RT and mouse movement; both vary systematically over 4 probability conditions (100, 80, 50 and 20 %), with lower RT and mouse movements displaying more direct trajectory to the target in high probability trials.
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The 16th Meeting of the European Society of Cognitive Psychology (ESC0P Conference 2009)