The Basketball Hoop Illusion

Michael K. McBeath

ABSTRACT

Observers typically underestimate the diameter of a basketball hoop relative to that of a basketball by 20% or more. This is independent of both viewing distance and exposure to the sport. Explanations such as a size/distance misperception are inconsistent with the accurate shooting exhibited in basketball. Findings support that this distortion is due in part to a tendency of observers to confound the width of the hoop with its projected area, and in part to their generally underestimating sizes of suspended objects. The distortion appears to represent a class of size illusions that occur with simple, familiar, closely-viewed, three-dimensional objects.

Results Confirming Perceptual Shrinkage(Estimates of Hoop/Ball Ratio and Light Diameter)

Hoop Memory Survey: median=1.50, %Error= -19%, mean=1.48 t(df=80)= -11.26, p<0.001

Hoop Perception Study: median=1.50, %Error= -19%, mean=1.56 t(df=35)= -4.13, p<0.001

Traffic Light Perception: median=8 in., %Error= -33%, mean=7.96 in, t(df=78)=-14.23, p<0.001

Viewing Distance:

  • Basketball Hoop: F(df=1,19)=1.89, p=n.s.
  • Traffic Light: R(df=3,75)=1.57, p=n.s. (i.e. no distance effect)

    • Results Supporting Perceptual Shrinkage of the hoop Due to the Net Tapering In and Supporting Perceptual Shrinkage of the Hoop Due to Elliptical Perspective

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