People use several visual signals to determine another person’s gaze, and a new study suggests that one of the smallest—the reflection of light on the eye’s surface—plays an important role when viewing conditions become challenging.
Known as eye glint, the feature consists of mirror-like highlights created when light reflects from the cornea and the eye’s moist surface. Researchers Gwenisha J. Liaw and Colin J. Palmer of the National University of Singapore examined whether the human visual system uses this reflection in a way similar to commercial eye-tracking cameras.
The researchers conducted three experiments with computer-generated three-dimensional faces. In each experiment, participants viewed faces with realistic eye glints or with the reflections digitally removed.
The first experiment involved 40 participants who viewed faces looking directly at them or slightly to one side under straightforward lighting. Participants reported whether the faces were making eye contact and used a mouse to indicate the perceived gaze angle. Under these conditions, the presence of eye glint produced no statistically significant improvement in accuracy or precision.
The second experiment introduced a more difficult condition by rotating the faces’ heads 20 degrees to the left or right. A head turn can make the iris appear to shift in a way that leads observers to misjudge gaze direction. With eye glint visible, participants made fewer errors and estimated gaze direction more precisely than when the glints were removed.
According to the researchers, the glint’s position on the iris remains relatively stable when the head turns. This can give the brain a reliable reference point for separating the direction of the gaze from the effects of the changed head position.
The third experiment tested the effect of lighting from a 45-degree angle to the left or right. Shadows can alter the apparent position of the iris and bias judgments of eye contact. Eye glints reduced this lighting-related bias, helping participants make more accurate assessments.
The reflection also changes according to the location of the light source. The researchers suggest that the brain may use this information to estimate the direction of the lighting and compensate for shadows across the face and eyes.
Only about half of the participants in each experiment said they noticed the eye glints. However, performance was nearly the same among those who reported seeing them and those who did not. This indicates that the visual system may process the cue automatically rather than relying on conscious attention.
The researchers noted that real-world lighting is constantly changing, which could make eye glint less reliable in some situations. However, because people typically shift their gaze several times per second, lighting may remain sufficiently stable during an individual glance for the reflection to provide useful information.
Future research will examine whether eye glint affects other social judgments, including the recognition of emotions and assessments based on facial appearance. The study, titled “Eye glint as a novel Perceptual Cue in human vision,” was published in Psychological Science.
Sources: PsyPost.