DEPTH AND SIZE PERCEPTION Problems for Perceiving Depth and Size Oculomotor Cues Monocular Cues Binocular Disparity Size Constancy

Problems for Depth and Size Perception The proximal stimulus is 2d, but the distal stimulus is 3d Size of the image is dependent on distance

Oculomotor Cues Information about eye position and eye muscles

Accommodation lenses are curved more to focus on closer objects not useful for distances more than 10 feet

Convergence eyes rotate inwards to focus on near objects not useful for distances more than 10 feet

Pictorial Monocular Cues occlusion - partly covered objects perceived as more distant relative size - larger objects perceived as closer familiar size - objects known to be larger are perceived as farther away than objects known to be smaller

Pictorial Monocular Cues relative height - higher objects perceived as more distant linear perspective - parallel lines converge with more distance

Muller-Lyer Illusion

Pictorial Monocular Cues texture gradient - finer textures perceived as more distant shadows - shaded areas perceived as further from light source atmospheric perspective - more distant objects appear blurred and bluish

Movement-Produced Monocular Cues movement parallax - closer objects move faster and in the opposite direction deletion and accretion - covering and uncovering of objects

Binocular Disparity Retinal images are different because the eyes are separated The closer the object, the greater the binocular disparity

Binocular Disparity Horopter - imaginary circle on which objects are focused at the same points on both retinas Angle of disparity - difference in location of points on the two retinas; increases with distance from the horopter

Binocular Disparity Crossed disparity - for objects in front of the horopter, the images move out toward the sides of the retinas Uncrossed disparity - for objects behind the horopter, the images move inward on the retinas

Size Constancy The size of an object is perceived as constant even when the size of the retinal image changes size-distance scaling - perceived size is based on retinal size and perceived distance

Emmert’s Law The more distant an afterimage appears to be, the larger it will seem S = K(RxD) S - apparent size K - constant R - retinal image size D - perceived distance