The Genetic Relationship Between Hand and Eye Dominance

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The Genetic Relationship Between Hand and Eye Dominance

Many studies have shown the correlation between the preferred eye for monocular tasks in Homo sapiens and hand dominance. This is generally referred to as trait asymmetry. Although its functional significance has not yet been determined, patterns of ocular dominance have been shown to be related to a large number of perceptual, performance, and clinical phenomena. (Porac, et al.) Eye dominance and its connection to hand dominance, more specifically, have been a particularly significant area of interest: Handedness and eye-dominance are undoubtedly associated statistically. (McManus, et al.) The purpose of this study is to recreate or discover any new correlations found between the dominant eye and handedness.

Research Question: Is there a correlation between hand dominance and eye preference for monocular tasks?Prediction: If a person is right hand dominant, they will also prefer their right eye for monocular tasks. Subsequently, if a person is left handed, their left eye will be dominant.

For the data analysis, we used a different type of statistical test called chi-square distribution using contingency tables, which is very similar to a normal chi-square test. The major difference is that our test compares the observed values compared to random, not to any expected values. First, it's necessary to do some calculations to obtain the expected values for the test if the data was completely random. Then, perform a normal chi-square test, which uses the equation: ∑〖(O-E)〗^2/EThis gives you the χ2 observed value. The p-value is obtained using a table of critical values. Our test is shown on the left.

“Eye Dominance, Writing Hand, and Throwing Hand.” McManus, I.C. Laterality: Asymmetries of Body, Brain and Cognition Vol. 4, Iss. 2, 1999. Web. 15 Apr. 2014. “The Dominant Eye.” Porac, Clare; Coren, Stanley. Psychological Bulletin, Vol 83(5), Sep 1976, 880-897 14 April 2014. “The binomial distribution of right, mixed and left handedness.” Annett, Marian. Quarterly Journal of Experimental Psychology Volume 19, Issue 4, 1967. 29 May 2007.

The Genetic Relationship Between Hand and Eye Dominance

Research Question/Prediction

Experimental Design

In this experiment, hand and eye dominance were tested to see if there was a correlation between them. The prediction was that right handed people would tend to be right eyed, and left handed people would tend to be left eyed. However, the prediction was disproven, as not all of the visual data supported the hypothesis. The graphs show an obvious correlation between right handedness and right eye dominance, with roughly 70% of the right handed population being right eyed as well. Left handedness, however, did not support the hypothesis or follow a similar tendency, as only 40% of the left handed sample was left eyed as well. To further analyize these results, a Chi Square Contingency Test was used. The calculated P-value was 0.5, so the null hypothesis was not rejected. There can be no accepted correlation in the data as there is a 50% probability that any correlation occured by chance. Therefore, it can be concluded that hand and eye dominance do not have a strong correlation. To improve results and eliminate error in this experiment, a larger sample size should be used. This would ensure more accurate data, and display truer percentages of the four combinations (RR, RL, LL, LR) in a population. Other experiment using larger sample sizes revealed a correlation, which shows that with a larger sample size, a more accurate result could be calculated.

Procedure A: Testing which eye is dominant 1. In order to ensure a variety in the sample size, approximately 40-50 people will be asked to participate in the experiment.2. Due to the fact that the majority of the population is right-handed, an equal portion of the subjects need to be predetermined as left-handed to ensure an equal amount of right/left-handed people. 3. Utmost secrecy is necessary for the success of the experiment. The subjects cannot be told beforehand that they are being tested for eye dominance as it can skew their decision of which eye they might use. 4. Ask the subject to make a triangle with their fingers and center the gap around a small piece of paper, three feet away from them. The paper will have a blue dot, which the subject will focus on through the gap. Ask the person to focus on the dot through the gap with one eye.5. Instruct the subject to decrease the gap in between their fingers until the object appears to be touching the edge of their hands. Since both eyes can’t see the object through a gap that small, people will naturally use their dominant eye and close their other eye in order to make the object appear to touch their hands. 6. Record the eye which the subject closed and which one stayed open. The eye that stayed open is the dominant eye. Procedure B (done after Procedure A): Testing which hand is dominant1. Perform the test on the same subjects who participated in Procedure A (listed above)2. Ask the subject to pick up a pencil and write their first and last name.3. Whichever hand they use to write with will be considered their dominant hand. Record all results.


Figure 1 (left): A diagram of the test for hand dominance (testing for which hand the subject writes with).


Figure 2 (right): A diagram of the test for eye dominance (which eye is instinctively preferred). The test subject will go through both hand dominance and eye dominance tests.

Figure 3 (left): A picture of the experiment in progress. To focus on the blue dot through the hands, the subject has to close one eye, leaving the preferred eye open.



Figure 4 and 5: Graphs for the correlation between hand dominance and eye dominance with data in the form of a percentage, the percentage being the number of subjects tested displaying a certain combination of traits over the number of subjects tested with that dominant hand. A percentage was necessary because the number of left hand dominant people tested was less than the number of right hand dominant people tested.

Data Analysis

Preferred Eye Preferred Hand Right Left TotalRight 23 (22) 10 (11) 33Left 9 (10) 6 (5) 15Total 32 16 48Chi-square Value: 0.4364 p-value: 0.5

Table 1 (above): Chi-Square contingency table for data analysis.


Table 2 (above): A sample of the data collected throughout the experiment. Only 10 out of the 5o samples are shown.




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