Examining the relationship between ssVEP and psychophysical measures of contrast sensitivity, grating acuity, and orientation discrimination.

Intuitively, we categorize individuals as good or poor performers. In vision, someone who performs well on one test is expected to do well on other tests. If so, test results should correlate with each other. However, studies have found low correlations between basic visual tests. One possible explanation is the detrimental influence of non-visual factors-such as attention or motivation-on correlations. To minimize these effects, we adopted steady-state visually evoked potentials (ssVEPs), which do not rely on subjective responses. 35 healthy participants performed contrast sensitivity, visual acuity, and orientation discrimination tests with psychophysics and ssVEPs. Although both methods showed high reliability, correlations between tests were weak. Thus, tests might target more specific aspects of vision than normally assumed. Furthermore, psychophysical and ssVEP measures did not correlate, suggesting that test outcomes depend on the method rather than the targeted visual abilities or that ssVEPs and psychophysics have different systematic errors.