Only Time will Tell the Future : Anticipatory saccades reveal the temporal dynamics of time-based location and task expectancy

Kurzfassung/Abstract

Humans form associations between time intervals and subsequent events and thus develop time-based expectancies that enable time-based action preparation. For instance, when each of two foreperiods (short vs. long) is frequently paired with one specific task (e.g., number magnitude judgment vs. number parity judgment) and infrequently with the alternative task, participants are faster to respond to frequent rather than infrequent foreperiod–task combinations. Here, we investigated the time course of time based task expectancy by measuring eye movements toward a left and right target location. Foreperiods predicted target locations with 100% validity and tasks with 90% validity. In 2 experiments, without having any explicit knowledge about the foreperiod–location or foreperiod–task contingencies, participants first moved their eyes to the location associated with the short foreperiod and then looked toward the location of the long foreperiod (if no stimulus had been presented after the short foreperiod had passed). That is, they proactively moved their eyes to optimize perception in line with the specific time and location they expected an event to occur at. Importantly, these eye movements reflected not only time-based location expectations, but also time-based task expectations. We discuss new insights in time-based expectancy and its temporal dynamics obtained from anticipatory eye movements and highlight spontaneous eye movements as a window into cognitive processes that cannot be assessed via behavioral response measures.