codes for emotional expressions, such as "R" which represents an action that occurs on the right side of the face and "L" for actions which occur on the left. An action which is unilateral (occurs on only one side of the face) but has no specific side is indicated with a "U" and an action which is bilateral but has a stronger side is indicated with an "A" for asymmetric. List of AUs and ADs (with underlying facial muscles) Main codes Head movement codes Eye movement codes Visibility codes Gross behavior codes These codes are reserved for recording information about gross behaviors that may be relevant to the facial actions that are scored. See also Computer facial animation Computer processing of body language Facial electromyography Facial feedback hypothesis Facial muscles Microexpression References External links Paul Ekman's articles relating to FACS Paul Ekman's Facial Action Coding System (FACS) More information on the different animal FACS projects New Yorker article discussing FACS Details from 1978 edition of FACS Site at WPI download of Carl-Herman Hjortsjö, Man's face and mimic language" (the original Swedish title of the book is: "Människans ansikte och mimiska språket". The correct translation would be: "Man's face and facial language") Facial expressions Encodings Anatomical simulation Animal communication