Synesthesia: a condition in which perceptual or cognitive activities trigger exceptional experiences. Study of how physical stimuli are translated into psychological experience. Jnd (just noticeable difference: small diff in the amount of stimulation that a specific sense can detect. Webers law: stating thagt the size of a jnd is a constant proportion of the size of the initial stimulus, weber fraction- constant proportion. Signal detection theory: involves decision processes and higher mental functions, four outcomes, hits- detecting signal when present, misses failing to detect, false alarms- detecting signals when not present, correct rejections- not detecting when they are absent. Sensory adaption importance: gradual decline in sensitivity to prolonged stimulation, allows people to ignore obvious and focus on changes in the environment, behavioral adaption sculpted by natural selection. Light is form of electromagnetic radiation that travels as a wave. Light passes through cornea/pupil/lens and falls on the retina. Lens: adjusts its curvature to focus the images.