ssVEP-based estimation of contrast sensitivity, visual acuity and orientation sensitivity further supports the absence of a common factor in vision

Steady-state visually evoked potentials (ssVEP), elicited by stimuli flickering at a specific frequency, are widely used in vision research and clinical settings as an alternative to behavioral tests. Despite their widespread use, the relationship between behavioral and ssVEP thresholds remains unclear. To address this, thirty-five participants viewed a grating stimulus flickering at a specific frequency with its contrast, spatial frequency, or orientation gradually adapted, to extract the EEG thresholds (no behavioral responses were given). The same participants also completed behavioral tests to assess contrast sensitivity, visual acuity, and orientation sensitivity. We first correlated the two measures systematically in all three conditions. Second, visual tests often correlated only weakly with each other in behavioral studies. We sought to determine whether reducing the influence of confounding factors, such as attention, motor execution, and response strategy, could uncover potential correlations between different visual tests. Despite good test-retest reliability for both methods, no significant correlations were observed between EEG and behavioral measures, suggesting that these two methods may assess distinct aspects of visual functioning. Additionally, correlations between different tests were small and non-significant, providing further evidence that there may not be a single factor underlying visual abilities. These findings suggest that low correlations between visual tests may not lie in the poor specificity of the tests but rather in the inherent independence of the mechanisms they measure.