Facial expression responsible for controlling the expression differ in each case. Voluntary facial expressions are often socially conditioned and follow a cortical route in the brain. Conversely, involuntary facial expressions are believed to be innate and follow a subcortical route in the brain. Facial recognition is often an emotional experience for the brain and the amygdala is highly involved in the recognition process. The eyes are often viewed as important features of facial expressions. Aspects such as blinking rate can possibly be used to indicate whether a person is nervous or whether he or she is lying. Also, eye contact is considered
Facial composite called "Identikit", was introduced in the U.S. in 1959; it used drawings of facial features on transparent acetate sheets that could be superimposed on one another to produce the composite image. (A later version of Identikit is made by Smith & Wesson.) In 1970, a system called "Photofit", which aimed for greater realism by using actual photographs of facial features, was introduced in the U.K. In the last two decades, a number of computer based facial composite systems have been introduced; amongst the most widely used systems are SketchCop FACETTE Face Design System Software, "Identi-Kit 2000", FACES, E-FIT and PortraitPad.