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Humboldt-Universität zu Berlin

The effect of gaze direction on unconscious visual processing

Die Masterarbeit von Apoorva Rajiv wurde mit dem Humboldt-Preis 2014 ausgezeichnet.

Laudatio

Apoorva Rajiv Madipakkam hat ihre Masterarbeit in der Neurologie an der Charité durchgeführt. Frau Madipakkam untersucht in ihrer neurowissenschaftlichen Studie anhand einer Serie von unterschiedlichen Experimenten die unbewusste Beeinflussung von Blickausrichtungen beim Menschen. Dabei bedient sie sich, methodologisch höchst anspruchsvoll, einerseits des sogenannten eye tracking sowie des functional magnetic resonance imaging (fMRI) und erhält für ihre beachtliche Leistung den Humboldt-Preis.

Zusammenfassung

Gaze direction is an important social cue that gives us valuable information about another person’s intentions and focus of attention. Evidence suggests that faces with direct gaze reach conscious awareness faster than those with an averted gaze. However, the behavioural effects and the neural correlates of this preferential processing of direct gaze outside of awareness remain unclear. To address these questions, we performed a behavioural experiment and a pilot functional magnetic resonance imaging (fMRI) study. Faces with direct and averted gaze were rendered invisible using interocular suppression. To ensure that faces were indeed invisible, we assessed participants’ awareness based on a subjective rating scale as well as objective criteria. During the experiments, we used eye tracking to monitor participants’ eye movements while they searched for the invisible faces with direct and averted gaze directions. This provided us with a direct measure of their behavioural responses during the unconscious processing of the stimuli. An analysis of the eye movements revealed that although participants’ were unaware of the faces, their eye movements were more often directed towards the faces with direct gaze. This shows the first clear behavioral evidence for an unconscious preference towards faces with direct gaze. These results offer a starting step for experiments in patient populations of disorders like autism and social phobia where evidence shows that there is an alteration in the gaze-processing network.

In a second step, we used fMRI to study the unconscious processing of eye gaze in the human brain. Our preliminary fMRI results indicated an enhanced processing of averted gaze in the fusiform face area (FFA) for invisible faces and a nearly significant enhanced processing of averted gaze for visible faces in the right amygdala. These results are novel as it shows for the first time a processing of gaze for invisible stimuli. Overall, our findings provide new insights into the processing of gaze directions, a vital component of social cognition and extend our current understanding about the scope of the visual system to unconscious stimuli.