Sidney K Hulsey¹, Alayna M McGuire¹, Sarah M Haigh¹; ¹University of Nevada, Reno

Flickering lights are common in modern environments, partly due to the efficiency and flexibility of light emitting diodes (LEDs). While certain flicker frequencies are known to produce a variety of visual symptoms including discomfort, illusions, migraines, eye fatigue, and seizures, little is known about its effects on cognition. LEDs can flicker at much faster rates than the standard 120Hz from older fluorescent lights. Originally, faster flicker was believed to be innocuous; however, the human visual system can resolve flicker at much higher rates during eye movements. The flicker is briefly apparent as a stripped pattern known as the phantom array. In this study, focused on how detection of the phantom array affects cognition, specifically errors during reading aloud. We compared phantom array detection accuracy under 600Hz flicker (where visibility of the phantom array is maximal), to number of errors when reading stripy and less stripy text under two flicker conditions: 600Hz and 60,000Hz (perceived as a steady light). Across nine participants, we found that participants made more errors when reading the stripy compared to non-stripy text (p=.034), particularly for the 60,000Hz flicker condition (p=.056). We also found that the number of errors made under the 600Hz flicker correlated with the accuracy in detecting the phantom array at 600Hz (r=.63). Together, this suggests that flickering light impairs reading and that the impairment is related to the sensitivity to flicker – in this case, the ability to detect the phantom array. Specific effects of flicker will support calls to regulate LED electronics to limit the effects of flicker on cognition in daily life.

Acknowledgements: Funding: ENDURE NINDS NS119709