Familiarity revealed by involuntary eye movements on the fringe of awareness

Abstract

Involuntary eye movements during fixation of gaze are typically transiently inhibited following stimulus onset. This oculomotor inhibition (OMI), which includes microsaccades and spontaneous eye blinks, is modulated by stimulus saliency and anticipation, but it is currently unknown whether it is sensitive to familiarity. To investigate this, we measured the OMI while observers passively viewed a slideshow of one familiar and 7 unfamiliar facial images presented briefly at 1 Hz in random order. Since the initial experiments indicated that OMI was occasionally insensitive to familiarity when the facial images were highly visible, and to prevent top-down strategies and potential biases, we limited visibility by backward masking making the faces barely visible or at the fringe of awareness. Under these conditions, we found prolonged inhibition of both microsaccades and eye-blinks, as well as earlier onset of microsaccade inhibition with familiarity. These findings demonstrate, for the first time, the sensitivity of OMI to familiarity. Because this is based on involuntary eye movements and can be measured on the fringe of awareness and in passive viewing, our results provide direct evidence that OMI can be used as a novel physiological measure for studying hidden memories with potential implications for health, legal, and security purposes.

Concealed information revealed by involuntary eye movements on the fringe of awareness in a mock terror experiment

“…In one study, the magnitudes of the P300 and the OMI strength in a visual oddball task were found to be weakly related 39 . Our results with different types of visual, auditory, and cross-modal oddball stimuli revealed a prolonged OMI as a function of the perceptual deviance 40,41 , but this marker of deviance could also be related to the pre-attentive Mismatch Negativity (MMN) potential of around 200 ms, observed even when attention is distracted from the oddball stimuli, or in patients with minimal consciousness 42 , i.e. without orienting.…”

“…It is now well established that concealed memories can be detected via physiological measures 1 . In a recent study 2 , we reported that involuntary eye movements and their inhibition during passive viewing are sensitive to face familiarity. This suggests a potential method for detecting concealed memories, which we successfully explored in the current study.…”

“…This resulted in reduced visibility, which observers rated in our previous study (identical paradigm, for the faces part) as "barely visible", on average 2 . The use of masking followed a previous attempt to detect face familiarity without masking, which did not show good results 2 , and another partly unsuccessful attempt to use RSVP (as in 18 , but using OMI and not P3 ERP). Bowman et al 46 have recently shown that famous (familiar) faces, but not novel (unfamiliar) faces break into awareness in RSVP, resulting in large differences between brain responses to the familiar and unfamiliar.…”

“…Faculty of Law, Bar-Ilan University, Ramat Gan, Israel. 2 School of Optometry and Vision Science, Faculty of Life Science, Bar Ilan University, Ramat Gan, Israel. * email: yoram.bonneh@gmail.com involuntary eye movements and the concealed information test.…”

“…* email: yoram.bonneh@gmail.com involuntary eye movements and the concealed information test. Given the ability to detect familiarity via differences in OMI in passive viewing 2 , we can consider its potential use for CIT. First, the use of masked stimuli on the fringe of awareness 18 reduces the ability for deception.…”