Perception l The process by which sensory input is organized and formulated into “meaningful experiences” l Nativism vs Empiricism

Perception l Sensation - the activity of sensory receptors and the resulting afferent transmission l Perception - is the activity of mediating processes which integrate present input with past input

Perception l At birth the human infant is basically a reflex organism l Stages of Perceptual Development A shift in the hierarchy of the dominant sensory systems An increase in intersensory integration Improvement in intrasensory discrimination

Perception l 1. In early stages of perceptual dev. There is a shift from the dominance of somatosensory receptors to greater utilization of visual and auditory l 2. Stimuli in the real world are multivariate & the ways in which they may be perceived vary; use of multicues

Perception l 3. Each sensory system develops a more precise ability for detecting, discriminating, recognizing, & identifying stimuli. l Hierarchial Ordering of Perceptual tasks detection discrimination recognition identification

Perception l How do we perceive that an object has: constant size, constant form, constant color l Despite: different distances, different perspectives, different illuminations

Perception l An enormous amount of integration and interpretation must occur in the brain to give us visual perception: image has 2 dimensions; we see 3 dimensions we perceive our world right side up; retina image is upside down disparities in retinal image; we see the actual size receive image with millions of separate cells in retina; we see a unified object

Perception l The eye must refract light rays so they focus on the retina l Refraction begins at cornea and continues in the lens l The lens can change its convexity by contracting the ciliary muscles

Perception l Visual Acuity Factors “graininess” the denseness of receptors in the retina fovea > density of cones 147,000 sqmm increasing number of receptors, both cones and rods which converge on each bipolar cell moving from the fovea to the edge of the retina

Visual Abnormalities l Hypermetropia (farsightedness); light focuses behind retina, correct with convex lens l Myopia (nearsightedness); light focuses in front of retina, correct with concave lens l Astigmatism

Visual Perception of Depth l Binocular Vision: coordinated employment of the (2) eyes in order to produce a single mental impression Monocular Cues: proximal size, brightness, partial overlap, shading, texture, linear perspective, movement parallax, & accomodation

Visual Perception of Depth l Binocular Cues: the differential feedback from eye muscles from accomodation & convergence on objects at different distances retinal disparity binocular parallax see diagrams on handout

Color Vision l Visual system reacts to specific wavelengths of radiant energy l Human retina has (3) light- sensitive pigments cyanolabe - the blue catcher chlorolabe - the green catcher erythrolabe - the red catcher

Color Vision l Color perception is produced by different wavelengths and color is the interpretation by the brain of certain wavelengths, projected onto the retina l If (2) or more wavelengths fall upon the retina simultaneously, the result is a color fusion

Color Vision l Qualities of Color Perception: Hue, or tone - a function of the wavelength; 750 nanometers = red, 400 nanometers = blue, the other hues are between Brightness - intensity of the light energy Saturation - white light combined with hue; low white light = > saturation

Figure-Ground Perception l One of the basic spatial organizing components of perception

Figure-Ground Perception l Seven classic differences between figure and ground: if (2) fields have a common border, the figure seems to have shape while the ground does not. The ground seems to extend behind the figure and not to be interrupted by the figure.

Figure-Ground Perception l Seven classic differences between figure and ground: the figure appears to be a “thing” to be object-like while the ground seems like unformed material the color of the figure seems brighter & more solid than that of the ground

Figure-Ground Perception l Seven classic differences between figure and ground: the figure tends to be perceived as closer to the observer than the ground, even though both are the same distance. The figure is more impressive and tends to be better remembered.

Figure-Ground Perception l Seven classic differences between figure and ground: the figure is more apt to suggest meaning; a common border between figure & ground is called a contour--the contour is shape producing, the contour shapes only the figure, the ground seems shapeless.