Contrasting Experimentally Device-Manipulated and Device-Free Smiles.
Level 2 - randomized trial
Controlled within-subjects laboratory experiment (by design analogy, not clinical CEBM)
PubMed 31681094 · doi:10.3389/fpsyg.2019.02297
What was done
A within-subjects laboratory experiment evaluated 159 participants across three 1-minute facial expression conditions: smile manipulation via Smile Stick, smile manipulation via chopsticks, and device-free smile. Facial electromyography measured muscle activation intensity in the zygomaticus major (cheeks) and orbicularis oculi (around the eyes). Participants also rated comfort, fatigue, difficulty, experienced positive and negative affect, and arousal levels after each manipulation.
What was found
The Smile Stick and chopsticks performed identically across all electromyographic and self-report measures. Device-free smiles produced significantly greater muscle activation than either device (by ~40% for the zygomaticus major and by ~15% for the orbicularis oculi). Device-free smiles were rated as most comfortable, most fatiguing, and produced the highest positive affect and lowest negative affect.
Why it matters
This study provides direct electromyographic evidence that common mouth-device manipulations do activate genuine smile musculature and induce affect changes, but to a substantially lesser magnitude than natural device-free smiling.
Limits
The abstract lacks demographic details, does not specify whether condition order was randomized or counterbalanced, and examines only brief 1-minute static holds in a laboratory setting without measuring downstream behavioral or cognitive tasks.
Cited by
- supports A genuine (Duchenne) smile is characterized by muscle activation and crinkling around the eyes in addition to movement of the mouth.