The technique relies on the assertion that the subject will subconsciously reveal their thoughts through very slight involuntary physical reactions, also known as ideomotor responses. The performer can determine what the subject is thinking by recognising and interpreting those responses. Muscle reading may be billed by some entertainers as a psychic phenomenon, where the audience will be told that by creating physical contact with the subject, a better psychic connection can be formed. In fact, the contact allows the performer to read more subtle reactions in the subject's motor functions that may not be apparent without contact, such as muscle control and heart rate.
