Research Design: Can a Visual Illusion Improve Sports Performance?

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RESEARCH DESIGN: CAN A VISUAL ILLUSION IMPROVE SPORTS PERFORMANCE?

Can a Visual Illusion Improve Sports Performance?

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You must read each slide, and complete any questions on the slide, in sequence.

Welcome

Can a Visual Illusion Improve Sports Performance?

Authors:

Kelly M. Goedert, Seton Hall University

Susan A. Nolan, Seton Hall University

Kaylise D. Algrim, Seton Hall University

Sports fans may be familiar with a phenomenon called quiet eye—when athletes stare directly at a point on their target without moving their eyes. Quiet eye is associated with greater success in a number of sporting activities, including free throws in basketball and putting in golf (Harle & Vickers, 2001). Jessi Witt and her fellow researchers (Witt, Linkenauger, & Proffitt, 2012) speculated that quiet eye may improve performance because focusing intently on a target may make the target appear bigger. The researchers hypothesized that if quiet eye works because it makes targets appear larger, so a visual illusion that makes targets appear bigger than their real size might also improve sports performance.

Two images with red circles in the center, one surrounded by six larger blue circles and one surround by eight smaller blue circles. Please move to the “Description” link for the full explanation.

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There are two images, both with a red circle in the center. The image on the left shows a red circle in the center with eight larger blue circles surrounding it in a ring. The image on the right shows a red circle in the center with ten smaller blue circles surrounding it in a ring. The larger blue circles make the red center circle appear larger, while the smaller blue circles make the red center circle appear smaller.

The researchers tested their hypothesis by manipulating the apparent size of a golf hole and measuring putting performance. Look at this picture. Which of the center circles appears larger?

The center circle on the left appears larger.

The center circle on the right appears larger.

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In the study, 32 participants putted a golf ball to a 5-centimeter golf cup. Each participant attempted a total of 20 putts. The researchers wrote, “A downward-facing projector displayed a ring of 11 small (3.8 centimeters in diameter) or 5 large (28 centimeters) circles around each hole to create an Ebbinghaus illusion.” For each illusion, participants “attempted 10 putts from a distance of 3.5 meters, and we recorded how many putts dropped into the hole” (Witt et al., 2012, p. 397). The researchers hypothesized that participants would make more putts when the hole was surrounded by smaller circles (making the golf hole appear larger) than when it was surrounded by larger circles (making the golf hole appear smaller).

How would you classify the design of this study?

This was a correlational study.

This was an experiment using a between-groups research design.

This was an experiment using a within-groups research design.

This was an outlier analysis.

Correct! This was an experiment, because the researchers manipulated an independent variable. It is a within-groups design because the same participants experienced all levels or conditions of the independent variable.

Actually, this was an experiment because the researchers manipulated an independent variable. It is a within-groups design because the same participants experienced all levels or conditions of the independent variable.

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Here is the description of the study again: In the study, 32 participants putted a golf ball to a 5-centimeter golf cup. Each participant attempted a total of 20 putts. The researchers wrote, “A downward-facing projector displayed a ring of 11 small (3.8 centimeters in diameter) or 5 large (28 centimeters) circles around each hole to create an Ebbinghaus illusion.” For each illusion, participants “attempted 10 putts from a distance of 3.5 meters, and we recorded how many putts dropped into the hole” (Witt et al., 2012, p. 397). The researchers hypothesized that participants would make more putts when the hole was surrounded by smaller circles (making the hole appear larger) than when it was surrounded by larger circles (making the hole appear smaller).

What was the independent variable in this experiment?

The independent variable in this experiment was the 32 participants.

The independent variable in this experiment was the number of successful putts that each participant made.

The independent variable in this experiment was the actual size of the golf hole, and its levels were larger or smaller.

The independent variable in this experiment was the apparent size of the golf hole, and its levels were larger or smaller.

Correct! The researchers manipulated the apparent size of the golf hole using the Ebbinghaus illusion to be larger or smaller than its actual size. The actual size of the golf hole did not change.

Actually, the independent variable was the apparent size of the golf hole. Remember: The independent variable is always the one that is manipulated by the researchers. Here, the researchers manipulated the apparent size of the golf hole using the Ebbinghaus illusion to be larger or smaller than its actual size. The actual size of the golf hole did not change.

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Here is the description of the study again: In the study, 32 participants putted a golf ball to a 5-centimeter golf cup. Each participant attempted a total of 20 putts. The researchers wrote, “A downward-facing projector displayed a ring of 11 small (3.8 centimeters in diameter) or 5 large (28 centimeters) circles around each hole to create an Ebbinghaus illusion.” For each illusion, participants “attempted 10 putts from a distance of 3.5 meters, and we recorded how many putts dropped into the hole” (Witt et al., 2012, p. 397). The researchers hypothesized that participants would make more putts when the hole was surrounded by smaller circles (making the hole appear larger) than when it was surrounded by larger circles (making the hole appear smaller).

What was the dependent variable in this experiment?

The dependent variable in this experiment was the 32 participants.

The dependent variable in this experiment was the number of putts each participant made.

The dependent variable in this experiment was the actual size of the golf hole, and its levels were larger or smaller.

The dependent variable in this experiment was the apparent size of the golf hole, and its levels were larger or smaller.

Correct! The researchers measured the number of putts each participant made.

Actually, the researchers measured the number of putts each participant made. Remember: The dependent variable is always the thing that is measured by the researchers and that is hypothesized to depend on the independent variable.

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We said that the dependent variable was the number of putts that each participant made. Which of the following accurately describes this variable?

It is discrete and ratio.

It is continuous and interval.

It is continuous and ratio.

It is discrete and ordinal.

Correct! The number of putts made is a discrete and ratio variable. It is discrete because it can take on only specific values (i.e., whole numbers), and it is ratio because zero is meaningful in this case.

Actually, the number of putts made is a discrete and ratio variable. It is discrete because it can take on only specific values (i.e., whole numbers), and it is ratio because zero is meaningful in this case.

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Here is the description of the study again: In the study, 32 participants putted a golf ball to a 5-centimeter golf cup. Each participant attempted a total of 20 putts. The researchers wrote, “A downward-facing projector displayed a ring of 11 small (3.8 centimeters in diameter) or 5 large (28 centimeters) circles around each hole to create an Ebbinghaus illusion.” For each illusion, participants “attempted 10 putts from a distance of 3.5 meters, and we recorded how many putts dropped into the hole” (Witt et al., 2012, p. 397). The researchers hypothesized that participants would make more putts when the hole was surrounded by smaller circles (making the hole appear larger) than when it was surrounded by larger circles (making the hole appear smaller).

What are the 32 participants?

They are the population.

They are a confounding variable.

They are an interval variable.

They are the sample.

Correct! The 32 participants are the sample.

Actually, the 32 participants are the sample.

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The researchers reported, “Participants made more successful putts when the 5-cm hole was perceptually larger” (Witt et al., 2012, p. 397). When putting to the hole surrounded by large circles, on average participants made 1.01 of their 10 putts, and when putting to the hole surrounded by smaller circles, on average participants made 1.75 of their 10 putts.

What do the numbers 1.01 and 1.75 represent?

Inferential statistics

Descriptive statistics

Outliers

Correlational statistics

Correct! These numbers summarize the observations in the study, so they are descriptive statistics.

Actually, these numbers are descriptive statistics, as they summarize the observations in the study.

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Recall that the researchers hypothesized participants would make more putts when the hole was surrounded by smaller circles (making the hole appear larger) than when it was surrounded by larger circles (making the appear smaller). Again, the researchers reported that when putting to the hole surrounded by large circles, on average participants made 1.01 of their 10 putts and when putting to the hole surrounded by smaller circles, on average participants made 1.75 of their 10 putts.

Are these reported results consistent or inconsistent with the researchers’ hypothesis?

The results are inconsistent with the researchers’ hypothesis because participants performed better, on average, when the hole appeared smaller.

The results are inconsistent with the researchers’ hypothesis because participants performed better, on average, when the hole appeared larger.

The results are consistent with the researchers’ hypothesis because participants performed better, on average, when the hole appeared larger.

The results are consistent with the researchers’ hypothesis because participants performed better, on average, when the hole appeared smaller.

Correct! The results are consistent with the researchers’ hypothesis that participants would putt better, on average, when the hole appeared larger.

Actually, the results are consistent with the researchers’ hypothesis that participants would putt better, on average, when the hole appeared larger.

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The bottom line: If you want to improve your performance at free throws, darts, or putting, then a quiet eye may help. The key is making your target appear larger than it actually is.

Determined female basketball player practicing free throws at school gym, playmates standing in line behind her

miodrag ignjatovic/E+/Getty Images

REFERENCES

Harle, S. K., & Vickers, J. (2001). Training quiet eye improves accuracy in the basketball free throw. Sport Psychologist, 15, 289–305. https://doi.org/10.1123/tsp.15.3.289

Witt, J. K., Linkenauger, S. A., & Proffitt, D. R. (2012). Get me out of this slump! Visual illusions improve sports performance. Psychological Science, 23, 397–399. https://doi.org/10.1177/0956797611428810