Manipulation of expended effort and intent does not affect estimates of slant or distance.

It is well known that people overestimate the orientation of both geographical and man-made sloped surfaces by between 5°-20°. More recently, work has shown that when people are encumbered by wearing a heavy backpack they overestimate hills and distances even more than a group not wearing heavy backpacks; however, the backpack manipulation has since been shown to be a demand effect-that is, being encumbered does not affect perception-it only biases those people influenced by it to give estimates the experimenters are seeking. Here we first show that expended effort and intent have never actually been manipulated between subjects in any of the work on steepness estimates, and expended effort has never been explicitly manipulated between subjects for distance estimates. When they are, they do not affect steepness or distance estimates. Our work is the first to experimentally manipulate effort and intent, to do this between subjects, while controlling for demand characteristics and checking to see whether the effort manipulation was effective. The experimental manipulation of effort and especially intent may be of benefit to parsing out perceptual effects from more cognitive or postperceptual processes in future work. (PsycINFO Database Record (c) 2019 APA, all rights reserved).