Subjective hypotenuse estimation: a test of the Pythagorean theorem.

The Pythagorean theorem constitutes a normative model for the estimation of the length of the hypotenuse of a right-angled figure. Tested with functional measurement methods, this mathematically correct model was inappropriate as a descriptive model. The problem was an orientation effect; hypotenuse estimates for vertically oriented figures were larger than those for horizontally oriented figures composed of the same lengths. Because of this discrepancy, no additive model could describe the judgments.