The effect of glare on simple reaction times

AGUIRRE R.C.; BARRAZA J.F.; COLOMBO E.M.

La Coruña, España

Congreso; 28th European Conference on Visual Perception; 2005

ECVP

Purpose. We investigated the effect of glare on reaction times (RTs) to achromatic sinusoidal gratings, for a variety of spatial frequencies and contrasts. Methods. Stimuli were generated on a Personal Computer and displayed on CRT monitor through a video attenuator to obtain higher contrast resolution. Glare was generated by using an incandescent lamp located 10 deg away from the line sight. Horizontal gratings were presented in a circular patch subtending 6.77 deg, with a mean luminance of 0.142 cd/m2. Viewing distance was 1.5 m.  The experiment was performed for spatial frequencies of 1, 2, 4, and 8 c/deg and for a wide range of contrast. Two levels of glare were used in addition to the no-glare condition, 15 and 60 lx measured between the two eyes. The experiment was performed in blocks containing all contrast values for each spatial frequency and glare level. Thirty measurements were carried out for each contrast to determine the average RTs. The stimuli were presented for 340 ms, with an  intertrial time randomly varying between 1000 and 3000 ms. During this time, the subject had to report by pressing a button of the mouse whether the stimulus had appeared. RTs shorter than 100 ms and longer than 2000 ms were discarded. Result. Results show that RTs increase with decreasing contrast for all conditions. When RTs are plotted as a function of the inverse of contrast they present a linear relationship. Interestingly, for all conditions, glare produces an increase of the slope of these lines, which means that, in presence of glare, RTs increase more rapidly with decreasing contrast.