Our eyes are always moving, although they are typically temporarily blocked in reaction to external stimuli (oculomotor inhibition [OMI]), depending on the stimulus saliency, anticipation, and attention. Previous studies indicated that auditory oddballs had longer OMI; however, they involved counting the oddballs, which might reflect deliberate attention. For a study, researchers determined whether the “passive” OMI response to auditory deviants offered a quantitative measure of deviance intensity (pitch difference) and how it varied with inter-trial delay (ITI). Participants sat concentrated in the center and passively listened to repeated brief sequences of pure tones that contained a deviant tone either on a regular or with a 20% chance (oddballs). Participants in an “active” control experiment counted the deviant or the standard.
Following the unusual deviant tone, the data demonstrated extended microsaccade inhibition and increased pupil dilation, as in prior investigations. The saliency effect indicated earlier inhibition initiation in proportion to pitch deviance, and a later release for oddballs, but only for ITI 2.5 seconds. The active control experiment yielded identical findings when counting the deviant but a longer OMI when counting the standard. The findings implied that OMI provided involuntary indicators of saliency and deviance that can be retrieved without the participant’s reaction.
Reference:jov.arvojournals.org/article.aspx?articleid=2778778
