Facial electromyography

Facial electromyography (fEMG) refers to an electromyography (EMG) technique that measures muscle activity by detecting and amplifying the tiny electrical impulses that are generated by muscle fibers when they contract.
It primarily focuses on two major muscle groups in the face, the corrugator supercilii group which is associated with frowning and the zygomaticus major muscle group which is associated with smiling.
Uses.
Facial EMG has been studied to assess its utility as a tool for measuring emotional reaction. Studies have found that activity of the corrugator muscle, which lowers the eyebrow and is involved in producing frowns, varies inversely with the emotional valence of presented stimuli and reports of mood state. Activity of the zygomatic major muscle, which controls smiling, is said to be positively associated with positive emotional stimuli and positive mood state.
Facial EMG has been used as a technique to distinguish and track positive and negative emotional reactions to a stimulus as they occur. A large number of those experiments have been conducted in controlled laboratory environments using a range of stimuli, e.g., still pictures, movie clips and music pieces.
It has also been used to investigate emotional responses in individuals with autism spectrum disorders.
Although commonly used as an index of emotional responses, facial muscle activity is also influenced by the social context in which it is measured. Using facial EMG in immersive virtual environments, Philipp, Storrs, and Vanman showed that even relatively impoverished social cues in a virtual environment can cause increases in zygomaticus major activity that are unrelated to self-reported emotional states.
In 2012 Durso et al. were able to show that facial EMG could be used to detect confusion, both in participants who admitted being confused and in those who did not, suggesting that it could be used as an effective addition to a sensor suite as a monitor of loss of understanding or loss of situation awareness.
Market research and gaming.
Two areas where facial EMG techniques have been used are in advertising research and in video gaming.
Advantages.
Proponents of Facial EMG point to the following advantages: