Illusory perceptions of space and time preserve cross-saccadic perceptual continuity

When voluntary saccadic eye movements are made to a silently ticking clock, observers sometimes think that the second hand takes longer than normal to move to its next position(1). For a short period, the clock appears to hav e stopped (chronostasis). Here we show that the illusion occurs because the brain extends the percept of the saccadic target backwards in time to just before the onset of the saccade. This occurs every time we move the eyes b ut it is only perceived when an external time reference alerts us to the ph enomenon. The illusion does not seem to depend on the shift of spatial atte ntion that accompanies the saccade. However, if the target is moved unpredi ctably during the saccade, breaking perception of the target's spatial cont inuity, then the illusion disappears. We suggest that temporal extension of the target's percept is one of the mechanisms that 'fill in' the perceptua l 'gap' during saccadic suppression. The effect is critically linked to per ceptual mechanisms that identify a target's spatial stability.