What is missing in the study of emotion expression?

Abstract

While approaching celebrations for the 150 years of “The Expression of the Emotions in Man and Animals”, scientists’ conclusions on emotion expression are still debated. Emotion expression has been traditionally anchored to prototypical and mutually exclusive facial expressions (e.g., anger, disgust, fear, happiness, sadness, and surprise). However, people express emotions in nuanced patterns and – crucially – not everything is in the face. In recent decades considerable work has critiqued this classical view, calling for a more fluid and flexible approach that considers how humans dynamically perform genuine expressions with their bodies in context. A growing body of evidence suggests that each emotional display is a complex, multi-component, motoric event. The human face is never static, but continuously acts and reacts to internal and environmental stimuli, with the coordinated action of muscles throughout the body. Moreover, two anatomically and functionally different neural pathways sub-serve voluntary and involuntary expressions. An interesting implication is that we have distinct and independent pathways for genuine and posed facial expressions, and different combinations may occur across the vertical facial axis. Investigating the time course of these facial blends, which can be controlled consciously only in part, is recently providing a useful operational test for comparing the different predictions of various models on the lateralization of emotions. This concise review will identify shortcomings and new challenges regarding the study of emotion expressions at face, body, and contextual levels, eventually resulting in a theoretical and methodological shift in the study of emotions. We contend that the most feasible solution to address the complex world of emotion expression is defining a completely new and more complete approach to emotional investigation. This approach can potentially lead us to the roots of emotional display, and to the individual mechanisms underlying their expression (i.e., individual emotional signatures).

High-resolution surface electromyographic activities of facial muscles during the six basic emotional expressions in healthy adults: a prospective observational study

“…The posed displays might be of idealized nature. Spontaneously displayed expressions can be more complex and can have an increased ambiguity of their emotional content 38 , 39 . To use HR-sEMG in the presented form for settings with spontaneously displayed expressions seems not to be feasible, because the electrodes and wiring would be too disturbing.…”

The Spatiotemporal Dynamics of Facial Movements Reveals the Left Side of a Posed Smile

“…We believe, however, that if the science of emotions were to remain still anchored in prototypical displays and static induction methods, it would not rise to the level of understanding the processes that evolved in response to real social contexts during the phylogenetic development of the human species. Having a comprehensive taxonomy of real emotion expression will help to formulate new theories with a greater degree of complexity (for a review, see [ 15 ]).…”

“…In this respect, three major models of emotional processing address the so-called “hemispheric lateralization of emotion” topic in humans [ 11 , 12 ]: the Right-Hemisphere Hypothesis [ 8 ], the Valence-Specific Hypothesis [ 13 ], and the Emotion-type Hypothesis [ 5 , 14 ]. Analysis of facial expressions has been a traditional means for inferring hemispheric lateralization of emotions by measuring expressive differences between the left and right hemiface, based on the assumption that the right hemisphere controls the left side of the face, and the left hemisphere controls the right side of the face [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. The Right-Hemisphere Hypothesis [ 8 ] states that all emotions are a dominant, lateralized function of the right hemisphere, regardless of their valence or the emotional feeling processed.…”

“…Th standard deviation of the reconstruction error was 0.2 mm for the vertical (Y) axis and 0 mm for the two horizontal (X and Z) axes. A major drawback of the existing literature on facial expressions is that, to collect reliable and controlled databases, researchers typically showed participants static images of posed expressions (for reviews, see [15,26]). Adopted stimuli were neither dynamic nor genuine, and the induction method [27] did not differentiate between Emotional Induction (i.e., the transmission of emotions from one individual to another [28,29]) and Motor Contagion (i.e., the automatic reproduction of the motor patterns of another individual [30,31]).…”

The Spatiotemporal Dynamics of Facial Movements Reveals the Left Side of a Posed Smile

“…Their faces were recorde frontally with a video camera (Logitech C920 HD Pro Webcam, Full HD 1080p/30fp Logitech, Lausanne, CH) positioned above the monitor for the FACS validation procedur The stimuli presentation was implemented using E-prime V2.0. Five infrared reflectiv markers (i.e., ultra-light 3 mm diameter semi-spheres) were applied to the faces of parti ipants according to the Clepsydra Model (Figure 1b, top picture [34]) for kinematic ana ysis. We selected the minimum number of markers adopted in the literature as a commo denominator to compare our findings with previous results [35,36].…”