Seeing social events: The visual specialization for dyadic human-human interactions

Detection and recognition of social interactions unfolding in the surroundings is as vital as detection and recognition of faces, bodies, and animate entities in general. We have demonstrated that the visual system is particularly sensitive to a configuration with two bodies facing each other as if interacting. In four experiments using backward masking on healthy adults, we investigated the properties of this dyadic visual representation. We measured the inversion effect (IE), the cost on recognition, of seeing bodies upside-down as opposed to upright, as an index of visual sensitivity: the greater the visual sensitivity, the greater the IE. The IE was increased for facing (vs. nonfacing) dyads, whether the head/face direction was visible or not, which implies that visual sensitivity concerns two bodies, not just two faces/heads. Moreover, the difference in IE for facing vs. nonfacing dyads disappeared when one body was replaced by another object. This implies selective sensitivity to a body facing another body, as opposed to a body facing anything. Finally, the IE was reduced when reciprocity was eliminated (one body faced another but the latter faced away). Thus, the visual system is sensitive selectively to dyadic configurations that approximate a prototypical social exchange with two bodies spatially close and mutually accessible to one another. These findings reveal visual configural representations encompassing multiple objects, which could provide fast and automatic parsing of complex relationships beyond individual faces or bodies.

Dynamic representations of faces in the human ventral visual stream link visual features to behaviour

Humans can rapidly extract information from faces even in challenging viewing conditions, yet the neural representations supporting this ability are still not well understood. Here, we manipulated the presentation duration of backward-masked facial expressions and used magnetoencephalography (MEG) to investigate the computations underpinning rapid face processing. Multivariate analyses revealed two stages in face perception, with the ventral visual stream encoding facial features prior to facial configuration. When presentation time was reduced, the emergence of sustained featural and configural representations was delayed. Importantly, these representations explained behaviour during an expression recognition task. Together, these results describe the adaptable system linking visual features, brain and behaviour during face perception.

Face Imagery Is Based on Featural Representations

The effect of imagery on featural and configural face processing was investigated using blurred and scrambled faces. By means of blurring, featural information is reduced; by scrambling a face into its constituent parts configural information is lost. Twenty-four participants learned ten faces together with the sound of a name. In following matching-to-sample tasks participants had to decide whether an auditory presented name belonged to a visually presented scrambled or blurred face in two experimental conditions. In the imagery condition, the name was presented prior to the visual stimulus and participants were required to imagine the corresponding face as clearly and vividly as possible. In the perception condition name and test face were presented simultaneously, thus no facilitation via mental imagery was possible. Analyses of the hit values showed that in the imagery condition scrambled faces were recognized significantly better than blurred faces whereas there was no such effect for the perception condition. The results suggest that mental imagery activates featural representations more than configural representations.