Diagnostic Features of Emotional Expressions Are Processed Preferentially

Abstract

Diagnostic features of emotional expressions are differentially distributed across the face. The current study examined whether these diagnostic features are preferentially attended to even when they are irrelevant for the task at hand or when faces appear at different locations in the visual field. To this aim, fearful, happy and neutral faces were presented to healthy individuals in two experiments while measuring eye movements. In Experiment 1, participants had to accomplish an emotion classification, a gender discrimination or a passive viewing task. To differentiate fast, potentially reflexive, eye movements from a more elaborate scanning of faces, stimuli were either presented for 150 or 2000 ms. In Experiment 2, similar faces were presented at different spatial positions to rule out the possibility that eye movements only reflect a general bias for certain visual field locations. In both experiments, participants fixated the eye region much longer than any other region in the face. Furthermore, the eye region was attended to more pronouncedly when fearful or neutral faces were shown whereas more attention was directed toward the mouth of happy facial expressions. Since these results were similar across the other experimental manipulations, they indicate that diagnostic features of emotional expressions are preferentially processed irrespective of task demands and spatial locations. Saliency analyses revealed that a computational model of bottom-up visual attention could not explain these results. Furthermore, as these gaze preferences were evident very early after stimulus onset and occurred even when saccades did not allow for extracting further information from these stimuli, they may reflect a preattentive mechanism that automatically detects relevant facial features in the visual field and facilitates the orientation of attention towards them. This mechanism might crucially depend on amygdala functioning and it is potentially impaired in a number of clinical conditions such as autism or social anxiety disorders.

Neurons in the human amygdala selective for perceived emotion

“…1B; two-tailed unpaired t test comparing average z scores within the ROIs: for fear-face trials, P = 0.51 for eyes and P = 0.36 for mouth; for happy-face trials, P = 0.68 for eyes and P = 0.14 for mouth], confirming that patients performed the task with a normal strategy. Both patients and controls primarily used information revealed by eyes to judge fear faces, whereas they used more mouth information to judge happy faces, consistent with previous studies (34,35).…”

“…Behaviorally, our epilepsy patients did not differ from healthy controls in terms of learning performance on the task, and both epilepsy patients and control subjects primarily used the eye region of the stimuli to correctly judge fear faces and primarily used the mouth region to correctly judge happy faces, findings consistent with prior studies (34,35). Forty-one out of 185 cells significantly differentiated the two emotions, and subsequent analyses indicated that these cells encoded the patients' subjective judgment regardless of whether it was correct or incorrect.…”

“…Compared with our previous neuronal classification images which were based on pixelwise analyses of face regions that drive neuronal response (17), we here used a fully independent permutation test to further illustrate that when eyes are more visible, the population of neurons can discriminate the emotions better (also see Table S2). Together with a substantial prior literature, this finding supports the idea that amygdala neurons synthesize their responses based substantially on information from the eye region of faces (18,21,34).…”

Neural processing of fearful and happy facial expressions during emotion-relevant and emotion-irrelevant tasks: A fixation-to-feature approach

“…Behavioural research presenting face parts (e.g., Calder, Young, Keane, & Dean,2000) or using response classification techniques such as Bubbles (e.g., Blais, Roy, Fiset, Arguin, & Gosselin, 2012;Smith et al, 2005) has highlighted the importance of these so-called "diagnostic features" for the discrimination and categorization of these facial emotions. Eyetracking research also supports the idea that attention is drawn to these features early on, as revealed by spontaneous saccades towards the eyes of fearful faces or the mouth of happy faces presented for as short as 150ms (Gamer, Schmitz, Tittgemeyer, & Schilbach, 2013;Scheller, Büchel, & Gamer, 2012). the most useful diagnostic information for the discrimination of fearful facial expressions and the mouth for the discrimination of happy facial expressions, and that the N170 peaks when these diagnostic features are encoded (Schyns, Petro, & Smith,2007).…”

Mapping of Facial Elements for Emotion Analysis

“…Several psychological studies [14] [9] [13] have demonstrated that humans look at specific locations of the face to identify emotions. These locations present diagnostic information described by features which are important for the analysis of emotional expressions.…”