Effect of noise on the contrast detection threshold in visual perception

It has recently been shown that noise can improve the detection of stimuli in several sensory modalities. We herein investigated whether visual contrast detection sensitivity can be improved by adding a certain amount of noise. The contrast detection thresholds of a light changing brightness periodically were measured either with or without overlapping noise in 22 normal participants. Sinusoidal modulating light at 1 or 15 Hz was used as a signal. White noise was used to produce random flickering light as the noise. Participants were required to detect any changes in the brightness of the signal with or without noise. The contrast detection threshold, which was measured using a psychophysical method, decreased at around the threshold level of the noise intensity. The maximum facilitatory effect was obtained at a noise intensity of 5 dB. This effect was consistently observed regardless of the frequency of the signal (1 and 15 Hz). These findings indicate that noise can improve the signal detection in human visual perception.