Singular or Summary: Averaging of Facial Expression in Sets is Modulated by Eccentricity

The visual system is believed to compress and represent abundant information through averaging. For example, when observers were asked to judge the orientation of a singular Gabor patch that was surrounded by others, the judgement approached the mean orientation of all Gabor (Parkes, Lund, Angelucci, Solomon, & Morgan, 2001). Recently, a similar effect was reported in complex face stimuli, where observers appeared to summarise the mean emotion when presented with a set of faces but were unable to identify the emotion in each individual (Haberman & Whitney, 2009). In our study, we investigated the relationship between eccentricity and averaging of emotional expression. The stimuli were created by morphing neutral with happy/disgusted expressions, where the resulting images ranged from 0 to 100%. The target face was either shown in isolation (baseline) or surrounded by eight flankers of the same identity. The flankers’ expression was either identical to the target or different from it (e.g. flanker 60% disgusted vs. target face 40% disgusted). The degree of difference between the target and flanker was varied from 0 to 100%. These were presented either centrally, or parafoveally. We asked observers to judge the emotional strength presented on the target face, on an 11-point scale. The effect of flankers was assessed by calculating the deviation between actual response and the emotion on the target face. We found a much larger significant effect of difference in the parafoveal location, where errors increased as a function of the difference in emotion within the set, which leaned towards the average emotion of the set. The results suggest that averaging of facial information is modulated by eccentricity. Haberman,J.,&Whitney,D.(2009).Seeing the mean: Ensemble coding for sets of faces. Journal of Experimental Psychology: Human Perception and Performance,35(3),718-734. Parkes,L.,Lund,J.,Angelucci,A.,Solomon,J.A.,&Morgan,M.(2001).Compulsory averaging of crowded orientation signals in human vision. Nature neuroscience,4(7),739-744. Meeting abstract presented at VSS 2013