Aging and the discrimination of 3-D shape from motion and binocular disparity

Abstract

Two experiments evaluated the ability of younger and older adults to visually discriminate 3-D shape as a function of surface coherence. The coherence was manipulated by embedding the 3-D surfaces in volumetric noise (e.g., for a 55 % coherent surface, 55 % of the stimulus points fell on a 3-D surface, while 45 % of the points occupied random locations within the same volume of space). The 3-D surfaces were defined by static binocular disparity, dynamic binocular disparity, and motion. The results of both experiments demonstrated significant effects of age: Older adults required more coherence (tolerated volumetric noise less) for reliable shape discrimination than did younger adults. Motion-defined and static-binoculardisparity-defined surfaces resulted in similar coherence thresholds. However, performance for dynamic-binoculardisparity-defined surfaces was superior (i.e., the observers' surface coherence thresholds were lowest for these stimuli). The results of both experiments showed that younger and older adults possess considerable tolerance to the disrupting effects of volumetric noise; the observers could reliably discriminate 3-D surface shape even when 45 % of the stimulus points (or more) constituted noise.

The effects of aging on the perception of depth from motion parallax

“…The results of the current study and the first experiment in Norman et al are not directly comparable, as the recovery of surface depth and shape information are different perceptual processes (see Norman et al, 2004, for a discussion); this difference is illustrated by the fact that Norman and colleagues found, in the same study, an effect of age for MP-defined shapes, but not for MP-defined suprathreshold surface depth. Older adults also have deficits in recovering structure from motion, compared to younger adults (Andersen & Atchley, 1998; Norman et al, 2008; Norman et al, 2013; Norman et al, 2000; Norman et al, 2012), though, again, structure from motion and depth from MP are different processes. However, when one considers that both processes require the use of motion information to recover form or surface depth information, and that one of these processes (structure from motion) is well-known to be affected by age, the age effects found in the current study are not unexpected.…”

“…Older adults have a well-documented deficit in motion perception, with higher thresholds for motion detection (Atchley & Andersen, 1998; Bennett, Sekuler, & Sekuler, 2007), motion direction discrimination (Ball & Sekuler, 1986; Snowden & Kavanagh, 2006), and speed discrimination (Norman, Ross, Hawkes, & Long, 2003). The recovery of structure from motion (a perceptual process related to that of depth from MP) is likewise affected by age (Norman, Bartholomew, & Burton, 2008; Norman et al, 2013; Norman, Dawson, & Butler, 2000; Norman et al, 2012), though it is unknown to what degree the neural mechanisms are shared (Nawrot & Joyce, 2006). Aging also affects pursuit eye movements—older adults have poorer pursuit accuracy than younger adults (measured as gains: eye velocity/target velocity) (Sharpe & Sylvester, 1978; Sprenger et al, 2011).…”

Motion perception as a model for perceptual aging

“…In contrast, the ability to discriminate 3D shape from visual stimuli moving in depth seems to be preserved during aging . The perception of 3D form and shape from other cues, e.g., binocular disparity, seems to be unaffected by age (Norman et al, 2008;Norman et al, 2012).…”

Binocular Perception of 2D Lateral Motion and Guidance of Coordinated Motor Behavior

“…Significant deficits in monocular motion perception are experienced by older adults (Norman, Ross, Hawkes, & Long, 2003;Wist, Schrauf, & Ehrenstein, 2000), and those in this population are often wholly unable to perceive depth and shape when specified by differential motion and static binocular disparity (Norman, Dawson, & Butler, 2000), especially in the presence of noise (Norman et al, 2012). However, these can be perceived accurately with dynamic binocular disparity, even in the presence of noise (Norman et al, 2006(Norman et al, , 2012, except under the most difficult of viewing conditions (e.g. high disparity combined with high-spatial frequency; Norman et al, 2000Norman et al, , 2008.…”