Abstract
Temporal expectations are predictions regarding the timing of events, that are formed based on previously-experienced temporal regularities. Two recent studies suggested that there is a tight link between eye movements and temporal expectations: prior to predictable visual targets, while expectations are being formed, saccades and blinks are inhibited. However, it is still unknown whether this pre-target oculomotor inhibition is related to the anticipation of a future predictable target, or to the process of timing itself, i.e. to the estimation of the duration of the interval prior to the target. The purpose of the present study was to examine this question by comparing a task that requires duration estimation (explicit assessment of time) with a task that requires anticipation of a target (implicit assessment of time). Trials consisted of two intervals (I1 and I2), each followed by a briefly (33ms) displayed tilted Gabor patches (S1 and S2). The duration of I1 was always 1s in the temporally-regular condition, and varied between 1–3s (0.5s increments) in the temporally-irregular condition. I2 was set individually per participant using a staircase procedure. During the implicit-timing condition, participants were required to judge which of the two Gabor patches was more vertically tilted. During the explicit-timing condition, participants were required to judge which of the two intervals was longer. Importantly, both condition were identical in their stimulation protocol and varied only by task. Saccade and blink rate were measured relative to the onset of S1. Results showed that temporal regularity led to pre-target oculomotor inhibition in both implicit- and explicit- timing conditions. These findings indicate that pre-target inhibition of eye movements is related to duration estimation rather than to anticipation of predictable targets. This is first evidence for a tight link between the cognitive process of duration estimation and control mechanisms of the oculomotor system.