Stare-in-the-crowd effect evolved from a necessity for fast and accurate gaze perception for complex social interactions (Emery 2000). According to this model, an eye direction detector (EDD) mechanism - a neurocognitive system responsible for the rapid detection of eyes in the environment and their gaze direction – arose as a function of the geometry created by a dark circular iris relative to the white sclera (Baron-Cohen 1994). Specifically, it is contended that the increased ratio of exposed sclera in the eye outline of humans serves to enhance the velocity and acuity of gaze direction perception (Kobayashi and Kohshima 2001). Baron-Cohen, S. (1994)
Human eye layer, known as the fibrous tunic, is composed of the cornea and sclera. The middle layer, known as the vascular tunic or uvea, consists of the choroid, ciliary body, pigmented epithelium and iris. The innermost is the retina, which gets its oxygenation from the blood vessels of the choroid (posteriorly) as well as the retinal vessels (anteriorly). The spaces of the eye are filled with the aqueous humour anteriorly, between the cornea and lens, and the vitreous body, a jelly-like substance, behind the lens, filling the entire posterior cavity. The aqueous humour is a clear watery fluid that is contained