Browsing by Author "Ukkonen, Emilia"

Objective. Earlier research has found that subjects with normal color vision and deuteranopes (who lack cone photoreceptors sensitive to green light alias green cones) perceive a dim red light faster than a blue light in darkness, whereas protanopes (who lack cone photoreceptors sensitive to red light alias red cones) perceive them as fast. Therefore, it seems that red cones have a strong effect on the perceived timing of the stimuli. By using a reaction time task, this study aimed to ensure that those results are due to the effect of red cones rather than an artefact caused by the subjects perceiving the colors of the stimuli. In addition, the aim was to study whether this speed difference has a direct effect on motor behavior. Methods. Four protanopes, four deuteranopes and seven subjects with normal color vision took part in the experiments. The intensity levels of the lights used in the reaction time task were determined based on detection threshold measurements. In the reaction time task, dim red and blue lights were presented to dark adapted subjects in a random order at ten visual degrees’ distance from fixation. Subjects’ task was to react to them as fast as possible by pressing a button. A generalized linear mixed model was fit to the data. Results and conclusions. The results showed that there was no difference in the reaction times to red and blue light for protanopes. Deuteranopes reacted to red light approximately 89 ms faster than to blue light, and subjects with normal color vision reacted to red light approximately 63 ms faster than to blue light. The intensity of the lights had little if any effect on the speed difference. The results indicated that observers with normally functioning red cones not only perceive red lights faster than blue light but also react to red light faster.