Interindividual variation in human visual performance

The responses of 20 young adult emmetropes with normal color vision were me asured on a battery of visual performance tasks. Using previously documente d tests of known reliability we evaluated orientation discrimination, contr ast sensitivity, wavelength sensitivity vernier acuity, direction-of-motion detection, velocity discrimination, and complex form identification. Perfo rmance varied markedly between individuals, both on a given test and when t he scores from all tests were combined to give an overall indication of vis ual performance. Moreover, individual performances on tests of contrast sen sitivity, orientation discrimination, wavelength discrimination, and vernie r acuity covaried, such that proficiency on one test predicted proficiency on the others. These results indicate a wide range of visual abilities amon g normal subjects and provide the basis for an overall index of visual prof iciency that can be used to determine whether the surprisingly large and co ordinated size differences of the components of the human visual system (An drews, Halpern, & Purves, 1997) are reflected in corresponding variations i n visual performance.