Perception of Gaze and Head Direction in Groups of Faces
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Gaze direction and head rotation are powerful cues that inform humans about another person’s attention, intentions and even emotion. Previous research has focused on understanding how people make judgements about individual faces in direct view. However in everyday life, people are often presented with groups of faces and need to judge where the attention of that group is directed, such as in group conversations or when giving presentations. This thesis presents research whose aim is to better understand how gaze direction and head rotation are perceived in the visual periphery and in groups. First, observers’ perception of gaze deviation in the visual periphery was tested, using psychophysical methods and modelling. The results showed that observers’ ability to judge gaze perception is severely limited, and that observers’ judgements are severely biased by head rotation in the visual periphery. Second, observers’ ability to perceive the average gaze or head direction of a group of spatially distributed faces was investigated. This was done using equivalent noise analysis, a technique which gives estimates for observers’ internal noise (how certain they are in their judgements of any individual face) and their effective sample size (how many faces they are able to combine into their average). The findings revealed that head rotation was averaged with less uncertainty and greater effective sample size than gaze deviation, suggesting that observers can more precisely and efficiently pool information about head rotation than gaze. Finally, averaging of heads and gaze stimuli presented in temporal sequences was analysed using the same equivalent noise technique and compared to spatial averaging. In sequences, the differences in processing between head and gaze direction disappear, suggesting that poor peripheral perception of gaze is the limit on our averaging of gaze cues.
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