Reaction Times to Different Colored Lights


Andrew Waltz

University of Colorado at Boulder, Fall 2007


When driving down the street there always seems to be certain colors that are used more often for signs and lights than others. This is done because it is thought that you will see them better and react faster to them. We wanted to know if these different colors really make a difference, so we tested the effects that different colored lights have on a person’s reaction time to that light. Since light energy decreases from blue to green to red to white, we predicted that reaction times would be fastest for blue light, followed by green light, followed by red light, then white light. Since different colored lights have different amounts of energy as determined by their wavelength, we hypothesized that higher energy light serves as a stronger stimulus to the eyes and the brain.

            To test this hypothesis we used a reaction timer with four different colored lights on it; blue, green, red, and white, decreasing in energy respectively. Ten individuals were randomly tested three times for each color of light using the reaction timer. Each individual tested could only use one finger to hit the buttons and they were each exposed to the same intensity of light.

            Our results showed no significant difference in reaction times to different colored lights. The average times of each light were .739 seconds for white light, .571 seconds for red light, .661 seconds for green light, and .728 seconds for blue light. We ran a T-Test on the data for the relationship between each possible pairing of colors and all the P values were all higher than 0.05, which indicated that our results were not significant.

            Our results were inconsistent with predictions based on our hypothesis since no correlation between light color and reaction time was found. Extremes in energy in either direction actually had the slowest times. The main problem with our experiment was that we had our light intensity set too low which made it hard for people to see the lights. There were also many peripheral distractions that might have influenced the results. A study by Martha Elliot entitled “Comparative Cognitive Reaction Times with Lights of Different Spectral Character and at Different Intensities of Illumination” found a significant correlation between reaction times and different types of light. These results may indicate that light energy does have an effect on reaction time. If we were to run another experiment, we would modify our hypothesis to be: if familiar lights from stop lights serve as a stronger stimulus from the eye to the brain, then average reaction times will be highest for green and red light.