Differences in Facial Expressions between Spontaneous and Posed Smiles: Automated Method by Action Units and Three-Dimensional Facial Landmarks

Abstract

Research on emotion recognition from facial expressions has found evidence of different muscle movements between genuine and posed smiles. To further confirm discrete movement intensities of each facial segment, we explored differences in facial expressions between spontaneous and posed smiles with three-dimensional facial landmarks. Advanced machine analysis was adopted to measure changes in the dynamics of 68 segmented facial regions. A total of 57 normal adults (19 men, 38 women) who displayed adequate posed and spontaneous facial expressions for happiness were included in the analyses. The results indicate that spontaneous smiles have higher intensities for upper face than lower face. On the other hand, posed smiles showed higher intensities in the lower part of the face. Furthermore, the 3D facial landmark technique revealed that the left eyebrow displayed stronger intensity during spontaneous smiles than the right eyebrow. These findings suggest a potential application of landmark based emotion recognition that spontaneous smiles can be distinguished from posed smiles via measuring relative intensities between the upper and lower face with a focus on left-sided asymmetry in the upper region.

Siamese Architecture-Based 3D DenseNet with Person-Specific Normalization Using Neutral Expression for Spontaneous and Posed Smile Classification

“…The visual analysis revealed that the distribution of the activation value of the proposed model appears around the eyes and lips, including the eyebrows, whereas in the case of the common method using a posed smile as the anchor, the activation value only appears in a portion of the face and not in the eyebrows. In particular, the visualizations obtained using the two models showed significant differences in the eyebrows and around the eyes, which is very important because the spatiotemporal features around the eyes have been used as the main features in related works [ 14 , 19 , 20 , 21 , 22 , 23 , 43 ]. This observation demonstrates that a more meaningful metric feature of the L1-norm distance layer can be extracted when using a neutral expression as an anchor than when using a genuine and imposter pair.…”

Smile Reanimation with Masseteric-to-Facial Nerve Transfer plus Cross-Face Nerve Grafting in Patients with Segmental Midface Paresis: 3D Retrospective Quantitative Evaluation

“…Movements of the orolabial region can be voluntary or spontaneous, contributing in different ways to our verbal and non-verbal expressions [7][8][9]. In the middle and lower parts of the face, lips opening may result from different neural pathways [10].…”

Review: Posed vs. Genuine Facial Emotion Recognition and Expression in Autism and Implications for Intervention

“…Few studies have utilized face stimuli of humans expressing genuine, spontaneous expressions of emotion, whether static or dynamic (Cassidy et al, 2014). This distinction is important because research has shown that the human brain, and artificial intelligence (AI) systems, process posed facial expressions differently compared to how spontaneous expressions of emotion are processed (Hess et al, 1989;Schmidt et al, 2006;Wang et al, 2015;Park et al, 2020).…”