What is EMG?
Electromyography (EMG) detects the electrical potential generated by muscle cells when these cells contract, and also when the cells are at rest. EMG thus measures the electrical activity of the muscles at rest and while contracting.
 

What is facial EMG?
Facial EMG (fEMG) studies typically focus on the facial muscle activities viz., the corrugator muscle (which lowers the eyebrow) and the zygomatic muscle (which controls smiling).
 

What muscles are measured in facial EMG?
Facial EMG measures electric activity in the corrugator muscle, which produces frowns and is an indicant of negative emotion, and the zygomatic muscle, which produces smiles and is an indicant of positive emotion.
 

Is facial EMG a valid measure?
Facial Electromyography (or fEMG) is a precise and sensitive method to measure emotional expression. Unlike self reports, fEMG does not depend upon language and does not require cognitive effort or memory. fEMG is capable of registering the response even when subjects were instructed to inhibit their emotional expression. It is also able to measure facial muscle activities to even weakly evocative emotional stimuli.
 

What is the advantage of facial EMG vis-à-vis functional MRI (fMRI)?
The study of the brain with imaging methods such as functional MRI (fMRI) is intriguing and potentially very informative. However it’s not yet understood what brain activation patterns are desirable, and current theory is too rudimentary to provide direction (Tierney, 2004). At this point fMRI studies are also prohibitively expensive and time consuming. In contrast facial EMG provides a simpler and probably more valid measure of emotional response.
 

What are the applications of facial EMG ?
Apart from academic studies, facial EMG is now used as a diagnostic tool in Advertising research. CERA (Continuous Emotional Response Analysis) which is based on facial EMG technique, permits second-by-second measurement of response to specific commercial elements. New application also includes using fEMG to measure emotional response while playing video games.  It has also been used in Human Computer Interaction studies.
 

What is CERA ?
Continuous Emotional Response Analysis (CERA) is a diagnostic tool developed by Gallup & Robinson to study audience reaction to television commercials. CERA takes our understanding of television commercial dynamics to levels not possible to probe with “pencil and paper” research. It is a state-of-the-art system that non-verbally measures emotional connections between advertising and its audience on a continuous basis.
 

How is Facial EMG different from EEG?
Electroencephalogram (EEG) testing records and measures the electrical activity of the brain. Typically, an EEG technologist attaches a cap with fixed electrodes on the head; the cap is hooked by wires to a machine that records electric activity on the brain. EEGs are considered to produce excellent records of post-synaptic potentials, especially those generated in the cortex, the cognitive center of the brain. However, they are not as effective in measuring activities in the amygdala, the emotional center of the brain, which is located deep within the median temporal lobes of the brain. Critics note that the meninges, cerebrospinal fluid and the skull "smear" the EEG signal, obscuring its intracranial source and have criticized EEGs as being a measure of ‘arousal’ instead of emotional response.