Becca Aguilar, Grace DeHoff, Allie Ferrara

Abstract: Effects of Different Stimuli on Reaction Times

Do people have a faster reaction time to a seen, heard, or felt stimulus? Based on the concept of electron receptors being the primary recipient of a given stimulus, estimated receptor numbers would vary directly to the surface area of a region available for the receptors to occupy. Therefore, it is reasonable to say that the skin will have the largest number of electron receptors due to its vast surface area. This would then be followed by either the ear or the eye depending on which has more surface area between the two, which we were unable to measure. We hypothesized that reaction times differ based on the number of electron receptors present in a stimulated area, then a felt stimulus will have the fastest reaction time due to the large surface area of the skin followed by a heard or seen stimuli.

In order to test our hypothesis, we used a reaction timer to equally measure the reaction times in response to a seen, heard, or felt stimulus. Reaction times were measured by a timer being activated when the stimuli was started, then stopped when the corresponding button was pressed by the subject. Seen stimuli were tested by different colored lights being illuminated; heard stimuli were tested with a buzzer sound, and felt stimuli were tested by a vibration felt through the fingers. We ran three trial runs on each subject and took the average values for each subject. We predicted that due to the difference in surface area of each sensory organ being tested, felt stimuli would have the fastest reaction time, followed by either the heard or seen stimuli.

Our results failed to reject our hypothesis because the calculated p-value from the first T-test that we ran between touch and sound showed a significant difference (mean= 0.695 seconds, P-value of 0.015) and the T-test between touch and sight showed a significant difference (mean=0.776 seconds, P-value of 0.007). However the T-test run between sight and sound did not show a significant difference (mean=0.776, P-value of 0.136). Our results were consistent with our hypothesis, showing an average of 0.46 seconds for felt stimuli, followed by 0.680 seconds for seen stimuli and 0.792 seconds for a heard stimulus.

Due to the loud environment within the classroom, reaction times of sound stimulus may have been affected. As a result of the brightly lit classroom, it may have been difficult to immediately see the light stimuli. Our biggest problem, however, was that in order to test vibration, we needed to turn down the intensity of the sound volume to its lowest possible level, therefore, the touch stimulus had a much lower intensity when compared to the heard and seen stimuli which were both tested at their full intensities.

We felt no need to modify our hypothesis since we failed to reject it; however, we did come up with alternate theories to base our hypothesis off of that could have yielded different results. An alternative theory that we could have based our hypothesis on is the different regions in the brain that each stimulus is processed in and how far a signal must travel to be processed. If this theory is used than it could be stated that a felt stimulus must travel from the stimulated area, through the spinal cord, to the brain, back through the spinal cord and finally to the finger to press the button signaling reaction. A heard stimulus is sent directly into the auditory canal and sent through the inner ear structure to the auditory never to the brain where it is processed as a sound and sent down to the finger to push the button. A visual stimulus is received upside down through the pupil, sent to the retina and flipped right side up and then travels along the optic nerve to the Cerebellum at the back of the brain where it is processed as an image and only after that has occurred can a signal be sent to the finger to push the button. Based on these routes of signal transfer, we could hypothesis that an auditory stimulus would have the fastest reaction time due to the ear having the shortest distance to send the signal followed by the eye and finally by a felt stimulus.