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Michael K. McBeath, Ty Y Tang; Basketball Hoop Illusion Verified both Empirically and through Comic Strip Caricatures. Journal of Vision 2019;19(10):199b. doi: https://doi.org/10.1167/19.10.199b.
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Introduction: The Basketball Hoop Illusion is a perceptual distortion in which distant, typically elevated, real-world, 3-D objects appear smaller than actual. We examined perceived size of basketball hoops and traffic lights, both empirically and by ascertaining extent that shrinkage is exaggerated within comic strips, and we confirmed geometric and cognitive factors contribute to the illusion. Methods: Observers estimated the size of an actual basketball hoop relative to the ball, or vice versa, while either holding a basketball, or with the ball placed under the basket. Observers also estimated the size of the glass lens on a traffic light from distances ranging from 20–500 feet. Participants were tested for susceptibility to classic geometric illusions potentially related to basketball hoop-size judgments, and were asked demographic questions. Finally, we assayed the hoop-to-basketball ratio from an assortment of a dozen different comic strips that contained basketballs and hoops at approximately equal implied viewing distances. Results: Observers reliably experienced a hoop-to-basketball ratio of 1.5 diameters, significantly below the veridical ratio of 1.85. The direction of estimate had no effect, nor did other demographic variables like sex, or sports expertise. Similarly, traffic light lenses were judged significantly smaller than actual (8 inches for standard 12-inch diameter lenses), independent of viewing distance. Experienced hoop shrinkage was found to be related to Müller-Lyer phenomena, and narrower rim-ovals appeared smaller. Finally, we verified that caricatures of hoops had hoop-to-ball ratios significantly below 1.5. Discussion: Our findings confirm that robust spatial illusions occur in naturalistic real-world environments like basketball or roadside settings, and that these distortions are consistent with classic geometric illusions. We corroborated that cartoons caricaturize and exaggeratedly shrink the size of basketball hoops relative to the ball. This is consistent with cartoons emphasizing notable features of observed stimuli, providing amplified representations of salient deviations from norms.
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