Determining the threshold for asymmetry detection in facial expressions. (2nd October 2013)

• Record Type: Journal Article
• Authors: Hohman, Marc H.; Kim, Sang W.; Heller, Elizabeth S.; Frigerio, Alice; Heaton, James T.; Hadlock, Tessa A.
• Is Part Of: Laryngoscope. Volume 124:Number 4(2014:Apr.)
• Page Start: 860
• Page End: 865
• Publication Date: 2013-10-02
• Subjects: Otolaryngology -- Periodicals; 617.51005
• DOI: 10.1002/lary.24331
• Languages: English
• ISSNs: 0023-852X

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="lary24331-sec-0001" sec-type="section"> <title>Objectives/Hypothesis</title> <p>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.</p> </sec> <sec id="lary24331-sec-0002" sec-type="section"> <title>Study Design</title> <p>Online survey.</p> </sec> <sec id="lary24331-sec-0003" sec-type="section"> <title>Methods</title> <p>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).</p> </sec> <sec id="lary24331-sec-0004" sec-type="section"> <title>Results</title> <p>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; <italic>X</italic><sup>2</sup> (6, N = 145) = 405.52 to 656.27, all <italic>P</italic> <0.001).</p> </sec> <sec id="lary24331-sec-0005" sec-type="section"> <title>Conclusion</title> <p>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.</p> </sec> <sec id="lary24331-sec-0006" sec-type="section"> <title>Level of Evidence</title> <p>4. <italic>Laryngoscope</italic>, 124:860–865, 2014</p> </sec> </abstract>