Psychological Research Into Pupil Size and Ratings of Attractiveness

Eye contact is the primary non-verbal way of indicating engagement, interest, attention and involvement. Research has found that people use their eyes to indicate interest. Disinterested people make little or no eye contact in a social context however when an individual is interested their pupil do indeed dilate.
Mutual gaze comprises of the length of gaze, the frequencies of glances and patterns of fixations, pupil dilation and blink rate and all are important cues in non-verbal communication. A first impression is a long lasting non-verbal communicator. It takes just 100ms for someone to judge and thus make a first impression. This is confirmed by Olson and Marshuetz (2005), who studied facial attractiveness and the minimal amount of time needed to appraise it.
Pupillometry refers to the measurement of variations in the diameter of the pupillary aperture of the eye. Pupillary constriction and dilation occurs primarily because of the light reflex and the accommodation reflex. The light reflex refers to constriction that occurs to intense light and dilation which occurs with dim light.
In humans the size of the pupil is controlled by involuntary constriction and dilation of the iris in order to regulate the amount of light that enters the eye. This is known as pupillary reflex. The pupil appears black because most of the light entering the pupil is absorbed by the tissues surrounding it inside the eye itself.
In a normal room light the human pupil has a diameter of around 3 or 4 mm. In a bright light this diameter reduces to just 1.5mm and in dim light the pupil enlarges to about 8mm.
When an individual looks at a visual stimulus their eyes are never still these are called saccades. Between saccades the eyes are relatively still during fixations lasting around 200-300ms. No new information is obtained during a saccade because the eyes are moving so quickly across the visual that the individual would only perceive a blurred image (Uttal and Smith, 1968)....