Sound/Light Stimulated Reaction Latency Resulting From Environmental Change

CU Boulder Fall 2008

Thomas Wong and Lauren Stanford


How dangerous is it to listen to the radio while driving? Music is simply an auditory distraction as are bright and flashy surroundings a visual distraction. We ran an experiment to determine if light or sound stimulated reactions better resisted the effects of sensory distraction. A bright environment should inflict little delay to reaction times towards light stimuli as light travels so fast that any reaction latency will be minimal. Distractive noises may also be speculated to inflict little delay to reaction times towards sound stimuli as the range of auditory reception is not limited to the front of a person.

We tested our hypothesis that light stimulated reactions are better able to resist distractions than sound stimulated reactions. We conducted light (LRT) and sound (SRT) reaction tests on five test subjects. Each test subject was given three stimuli of each type in a quiet dimly lit hallway followed by another set of tests in a bright noisy classroom. The test subjectsŐ reaction times were recorded for each environment and compared. The quiet environment acts as control data for each test subject where sensitivity to light and sound is maximized by singling out stimuli. Our control variables consisted of: giving each person a random assortment of high intensity light and sound stimuli, taking people to the same locations, and playing a song at constant volume in the classroom to maintain a minimum level of auditory distraction.

We predicted that any latency from the quiet to the distracted environment in the LRT will be less than that of the SRT. The reaction time latency from changing environments was calculated by comparing the mean reaction times of the pseudo-replicate trials for each test subject in each environment. Changing the environment slowed reaction times in the LRT by 6.9% compared to 18.7% for the SRT. However, because of the effect from an outlier in the data, the results were statistically insignificant (t-test, t=2.78, p=.572). Data analysis without the outlier made results more significant but not within acceptable bounds (t-test, t=3.18, p=.145).

Our data even without the outlier was not significantly different; therefore, we concluded that this experiment contains unforeseen and underlying variables that also effect light and sound reaction latency. Qualitatively, light stimulated reactions appear to have a better ability to resist changes in environment than sound stimulated reactions. However the data of this experiment shows an insignificant relationship between the values of reaction lag for the LRT and SRT with a change in environment. We believe multiple, unexpected, variables in combination with the outlier impact in a small test population returned insignificant differences in our results.

It is paramount to determine underlying factors in light and sound stimulated reactions. Past studies relating to our experiment suggest underlying factors such as: gender, hand dominance, pupil color, color sensitivity etc. Modifications/qualifications to our hypothesis cannot be valid until we determine the effect, or lack of effect, of underlying factors. Methods employed by past studies include increasing testing populations and specifying more stringent control variables.