Lip and nonpreferred forearm EMG activity as a function of orienting task

Subjects performed orthographic or semantic orienting tasks while preparing an overt response (pressing one of two buttons). Electromyographic (EMG) activity of lip and nonpreferred forearm muscles and heart rate were monitored. Only lip EMG activity distinguished the extent of covert processing, evidencing greater activity during the semantic than sensory task. In contrast, increased nonpreferred forearm EMG and cardiac activity accompanied the behavioral response. It was concluded that general semantic and autonomic activity serve biological needs, but in addition, there are specific patterns of physiological response that are intrinsic to convert information processing.