THE INTERACTION AND INFLUENCE OF VISUAL AND AUDITORY STIMULI


Kristina Swartz (05kaswar@alma.edu)
Rebecca Ross (04rlross@alma.edu)
Steve Whetstone (deaf_pride@hotmail.com)


Alma College



In their article ÒVisual illusion induced by sound,Ó authors Shams, Kamitani and Shimojo (2002) report that when a single flash of light is presented with several auditory beeps, the flash of light is seen by subjects as more than one flash (147). To illustrate the influential effects of visual and auditory perceptions, we chose to measure perceived speeds of stimuli against actual speeds.
We expect a difference in actual and perceived speeds. We also expect this difference to show that the audio stimulus has a greater effect than the visual stimulus, and that all perceived speeds of visual and audio stimuli will be most affected by the audio stimulus.

Methods



Subjects:
Fourteen Alma College students (7 female, 7 male) were subjects for this experiment.

Apparatus/Stimuli:
The Eye Lines computer program was utilized to present the flashing visual stimulus in our experiment. The Macintosh MetroGnome program provided the pulsing audio stimulus.

Procedure:
We first presented each subject with all possible audio and visual stimuli speeds to familiarize them with the rating scale. Both the audio and visual stimuli have four possible speeds: five pulses or flashes per second, 2 pulses or flashes per second, 1 pulse or flash per second, and 1 pulse or flash per two seconds.

There are sixteen possible stimuli sets made up of each combination of the four visual and four audio speeds. Each subject was presented with all sixteen possible sets twice for a total of thirty-two stimulus sets. Each of the thirty-two sets were rated once for perceived visual speed and once for perceived audio speed. This yielded a total of sixteen sets rated for visual speed and the same sixteen sets rated for audio speed.

The order of presentation for the stimuli sets was completely random. Subjects were asked to alternate between rating the speed of the visual stimulus for four sets and rating the speed of the audio stimulus for four sets. The purpose of this alternation was to ensure that subjects did not become adapted to recognition of one stimulus over the other.

Once thirty-two sets of data were collected from all fourteen subjects, we averaged their perceived speed ratings and measured them against the actual stimuli speed.

Results



We measured the perceived audio stimulus rate against the actual visual stimulus rate and found that the visual stimulus did not greatly affect perception of the audio stimulus speed. We also measured the perceived visual stimulus rate against the actual audio stimulus rate and found that the audio stimulus had a more significant affect on the perception of the visual stimulus speed. These findings support our original hypothesis.





Discussion



When subjects were asked to rate the audio speed in the presence of the visual stimulus, their perceptions were close to the actual audio speeds. However, when subjects were asked to rate the visual speed in the presence of the audio stimulus, their perceptions were significantly deviant from the actual visual speeds. This strongly suggests that these visual speed perceptions were greatly affected by the presence of the audio stimulus.

References



BEAGELEY, W.K. (1990). Eye Lines [computer program]. Alma, MI. Alma College.

SHAMS, LADAN, Yukiyasu Kamitani and Shinsuke Shimojo. "Visual illusion induced by sound." Cognitive Brain Research. Vol. 14:1 (June 2002) 147-152.

SHERHOUSE, BRAXTON (2002). MetroGnome [computer freeware]. Macintosh Computers. www.macmusic.org/softs/soft.php/lang/EN/id/176/


Alma College Psychology Department