A simple visual task to assess flicker effects on visual performance

Temporal modulation of lighting at frequencies higher than the critical fusion frequency can affect human efficiency in diverse ways that are not understood. A simple visual search task was used to assess visual performance under lighting with low (3%) and high (32%) temporal modulation and compared with the results of a conventional discrimination task in an identical situation. Even when side-by-side subjective appraisal corroborates that there are no visually perceptible differences between the two forms of lighting, both tasks show a reduction in visual performance when temporal modulation increases. Significantly larger relative differences between the two levels of modulation and better discrimination between individuals were obtained with the visual search task, demonstrating that the search task could be more useful for identifying individuals sensitive to flicker. The reasons why the visual search task might be more sensitive to flicker than the discrimination task are discussed.