People coordinate the force of their actions with the visible distances to objects and surfaces in their surroundings (Rieser, Ashmead, Talor, and Youngquist. 1990). This experiment is to test whether or not eye dominance affects how a person perceives depth. Witmer and Sadowski (1998) report on a study where people are tested on distance judgments obtained by nonvisually guided locomotion. They showed that when the subjects were given feedback, that is, they were allowed to see where they ended up after walking blindfolded, they performed better than those not given feedback. Also, it is shown that there was less error for closer distances than far ones. In Scharine and McBeath’s article (2002), they claim that a person walking blindfolded tends to veer to the right. Two factors that may explain this tendency are handedness and eye dominance. In this experiment we are interested in seeing how binocular disparity and eye dominance affect nonvisually guided locomotion.
The subjects were fifteen randomly selected Alma College students. The experiment was conducted at the Stone Recreation Center on the MAC court. This is the basketball court on the east side of the building. This court was chosen because it has walls around it to lessen the disturbance from other people using the facility at the same time. The subjects were tested one at a time. The experimenters checked the subjects for eye dominance by having them stand directly under the basketball net, facing in towards the court. Next, they were instructed to line their fingers up with the opposing basketball net in the distance. The subjects were then asked to close first one eye and then the other, and report how the positioning of their fingers appeared to change. The eye that showed no change is the dominant eye. Also, the subject’s handedness, that is, what hand they prefer to use, was recorded on the data collection sheet. The subject stood at a location specified by the experimenters. The experimenters then tied a bandanna over the participant’s eyes to completely eliminate visual stimulation and feedback. Subjects were asked to briefly remove the blindfold and stare at a big orange clock/timer placed a certain distance away for ten seconds. The subject then replaced the blindfold and walked to the place where he or she thought the object was located. The experimenters measured the distance from the object to where the subject stopped. The subject was led back to the starting point blindfolded, without any feedback as to how close or far away they were. This experiment was done thrice per distance (18 ft, 48 ft and 87 ft). The first time the subject viewed the object with both eyes open. The next time it was viewed with just one eye open. Finally, the object was viewed with the other eye open.
Table 1 shows how many times a subject deviates from the line per eye dominance/handedness. The majority of subjects had greater deviations in the direction that matched their eye dominance, with one exception. Those with right eye dominance and left hand dominance deviated equally between the left and right. The data in Table 1 also indicate that there were more left-handed subjects than right-handed ones.Figure 1 shows the average distance error for each group of eye conditions and distances. The data in Figure 1 show that with the distance of 18 feet, there was an average of less than 20 inches of error. With the distance of 48 feet, the average error was between 50 and 60 inches, and with the distance of 87 feet, error was an average between 170 and 180. The average was greatly increased as the distance was increased. On average, we also found the least amount of error when subjects were permitted to use only one eye, instead of both eyes.
An increase in error when participants were allowed to use both eyes went against what we anticipated. We thought that there would be less deviance and less distance error when using both eyes because both eyes would be able to work together to create a better visual. However, after reviewing our methods, we seemed to find a logical explanation. Participants were asked to judge three different distances with both eyes, then they were asked to only use one eye. At no time were subjects ever given any feedback as to their accurateness. After appraising Farrell and Thomson's data (1998), we feel that their conclusions also support our data. As the subjects repeated the experiment with the same distances (and different visual cues) their accuracy increased. Because they never got any feedback, it can be assumed that our participants were also continuously updating their position as they moved. As they repeated distances, they gained more familiarity with their environment and practice, allowing them to improve at continuous updating. Greater deviations in the direction that matched eye dominance supports our hypothesis. When a person closes their dominant eye, objects tend to appear to “move positions” in that direction. So, if a person were to close their dominant eye, and then try to navigate, it is possible that their skewed view of the world could run over into other areas of perception. Under this theory, a person who used cues only from a non-dominant eye would experience this run over, and walk in the direction of their visual misconceptions. Therefore, receiving visual cues from a non-dominant eye really does impair a person’s abilities in nonvisually guided locomotion.
Farrell, Martin J. and Thomson, James A. (1998). Automatic Spatial Updating During Locomotion Without Vision. The Quarterly Journal for Experimental Psychology. Vol. 51A No. 3. 637-654.
Rieser, John J., Ashmead, Daniel H., Talor, Charles R. and Youngquist, Grant A. (1990). Visual Perception and the Guidance of Locomotion Without Vision to Previously Seen Targets. The Quarterly Journal for Experimental Psychology. Vol. 19 No. 5. 675-689.
Scharine, Angelique A. and McBeath, Michael K. (2002). Right-Handers and Americans Favor Turning to the Right. Human Factors. Vol. 44 No. 2. 248-256.
Witmer, Bob G. and Sadowski, Wallace J. Jr. (1998). Nonvisually Guided Locomotion to a Previously Viewed Target in Real and Virtual Environments. Human Factors. Vol. 40 No. 3. 478-488.