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Determining the threshold for asymmetry detection in facial expressions
Author(s) -
Hohman Marc H.,
Kim Sang W.,
Heller Elizabeth S.,
Frigerio Alice,
Heaton James T.,
Hadlock Tessa A.
Publication year - 2014
Publication title -
the laryngoscope
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.181
H-Index - 148
eISSN - 1531-4995
pISSN - 0023-852X
DOI - 10.1002/lary.24331
Subject(s) - asymmetry , eyebrow , facial symmetry , facial expression , eyelid , psychology , audiology , medicine , physics , communication , ophthalmology , social psychology , quantum mechanics
Objectives/Hypothesis To quantify the threshold for human perception of asymmetry for eyebrow elevation, eye closure, and smile, and to ascertain whether asymmetry detection thresholds and perceived severity of asymmetry differ in distinct facial zones. Study Design Online survey. Methods Photographs of a female volunteer performing eyebrow elevation, eye closure, and smile were digitally manipulated to introduce left‐to‐right asymmetry in 1‐mm increments from 0 mm to 6 mm. One hundred and forty‐five participants viewed these photographs using an online survey, measuring accuracy of asymmetry detection and perceived expression unnaturalness (on a scale of 1–5). Results Photographs of facial asymmetries were correctly judged as asymmetrical over 90% of the time for 2 mm or more of asymmetry in eyelid closure, and 3 mm or more of asymmetry during smiling. Identification of eyebrow elevation asymmetry gradually rose from 23% correct to 97% correct across the range of 1 mm to 6 mm of asymmetry. Greater degrees of asymmetry were ranked as significantly more unnatural across all expressions (3 tests; X 2 (6, N = 145) = 405.52 to 656.27, all P <0.001). Conclusion Thresholds for asymmetry detection vary across different zones of the face; once detected, asymmetry in eyelid position is perceived as more unnatural than asymmetries in either brow elevation or smile. These data will inform counseling of patients with segmental facial weakness and may provide more objective goals for facial reanimation procedures. Level of Evidence 4. Laryngoscope , 124:860–865, 2014