Exploring Human Cognition From Eye-Movements: Is There Unconscious Visual Information?

In this study, we investigate whether fast-vanishing visual stimuli can carry information that affects human behavior, even when individuals report not seeing it. The impact of fast-vanishing cues on oculomotor functions can impact our understanding of the role of high-frequency fixational eye movements as well as human cognition in general. It may also inform technological developments, in particular, on the potential impact of high-frequency cameras and screens. For this purpose, we designed an experiment with two main tasks. In the control task, we estimate how fast a stimulus should be to escape conscious detection. We find that when it is presented during 1/120s or 1/240s, participants do not notice this fast stimulus most of the time. In the second part of the experiment, we use this stimulus as a cue to where a visible target will appear for one second. We find that, even when the probability of consciously registering the presence of a cue is as small as 0.02, its presence has a significant impact on saccade reaction times (SRTs). For all cue durations tested, {1/60, 1/120, 1/240} s, the probability of SRTs being impacted by a cue is greater than the probability of (consciously) reporting its detection. We argue that a cue having an impact on SRTs even when it is not noticed is evidence of unconscious visual information.