ABSTRACT
In an earlier experiment (Oudejans, Michaels, & de Vries, 1993—this volume), we tested whether time-to-contact (tc) judgments depended on linear optical size or the optical area of approaching objects by manipulating the visibility of an approaching object; the object was either fully visible or visible only through a slit. Observed differences revealed that judgments depended neither on the linear expansion nor on the entire optical area, but on the average optical size of the object in the horizontal and vertical dimensions (termed rbar). Moreover, judgments did not depend on tau; instead, https://www.w3.org/1998/Math/MathML"> r • b a r https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315799506/e3000455-006b-47f3-8dc3-986527b32979/content/inline-math_53_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> accounted for almost all of the variance. This optical variable is the derivative of rbar and equals https://www.w3.org/1998/Math/MathML"> r • https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315799506/e3000455-006b-47f3-8dc3-986527b32979/content/inline-math_54_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> in the case of a fully visible square, and https://www.w3.org/1998/Math/MathML"> r • / 2 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315799506/e3000455-006b-47f3-8dc3-986527b32979/content/inline-math_55_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , in the case of viewing through a slit.
