In the blink of an eye - Value and novelty drive saccades

Cavanagh Sean, Malalasekera Nishantha, Kennerley Steve 2015.


Evidence accumulation is an essential component of value-based de-cisions. Recent human studies suggest that overt attention correlates withe vidence accumulation necessary for optimal decisions. However, the in-fluence of covert attention on decision-making remains relativelyunexplored.To investigate this issue, two monkeys were trained to perform a decision-making task where they chose between two stimuli, which were either ‘Overtrained’ or learned that day (‘Novel’). Subjects could freely saccadeduring choice evaluation and indicated their decision by moving a joystick.Saccades were made within 170 ms of stimulus presentation and werestrongly driven by both value and novelty, implying covert stimulusevaluation prior to saccade. This effect was strongest for‘Overtrained’choices, but rapidly emerged during learning of‘Novel’choices. Thoughnovel stimuli attracted initial saccades,final decisions were guided only byvalue; implying attentional value comparison processes are at leastpartially dissociable from value comparison processes that govern final decisions. While subjects made highly optimal decisions, they frequently viewed only one stimulus; final choice was thus best explained by assuming covert evidence accumulation. Our results suggest that the pri-mate brain contains multiple value comparison systems for guiding attention toward highly valuable or novel information while simulta-neously optimizingfinal decision value.