How do we maintain a stable perceptual world despite moment-to-moment variations in input stimulation? Distal vs. Proximal Stimulus Unconscious inference vs. higher-order patterns in the stimulus Lightness Constancy Shape Constancy Size Constancy

Sensory physiology Physiological psychology Psychophysics creativity Perception Sensory physiology Physiological psychology Psychophysics Physical Stimulus Physical Stimulus Physiological Response Sensory Experience Sensory Experience creativity memory motivation attention learning

Lightness constancy Shape constancy Size constancy One’s judgment of an object’s lightness remains constant under varying levels of illumination. Shape constancy One’s judgment of an object’s shape remains constant at varying viewing angles. Size constancy One’s judgment of an object’s size remains constant at varying distances.

The Gelb effect: dim ceiling light screen black disk white disk unseen The observer ignorant of the spotlight will judge the black and white discs to have equal brightness. unseen spot light (on) observer sits here

The Gelb effect: dim ceiling light screen black disk white disk unseen white piece of paper screen black disk white disk unseen spot light (on) The observer ignorant of the spotlight will judge the black and white discs to have equal brightness. A piece of paper thrust into the light beam, however, makes it obvious that the left disc is black. observer sits here

Incident light (illumination) Reflected light (luminosity) Albedo = Incident light (illumination)

Observer has matched this stimulus that is under low illumination to the target on the left that is under high illumination

The observer’s matched stimulus exactly as before, now under the same bright illumination

Trapezoid or flat rectangle?

Cues for distance or depth (depth perception) 1. Binocular cues Convergence (oculomotor)* Retinal disparity *…involves kinesthetic feedback

Convergence as a binocular depth cue: (The role of kinesthetic feedback)

2. Monocular cues Non-motion Motion Motion parallax Optic flow Accommodation (oculomotor)* *…involves kinesthetic feedback Pictorial (static) cues Interposition Texture gradients Light and shadow Linear perspective Aerial perspective Horizon

Interposition (occlusion)

Texture gradient as a monocular depth cue

Light and shadow as a monocular depth cue

Linear perspective

Aerial perspective as a monocular depth cue

(Appears farther) (Appears closer) (Appears closer) (Appears farther)