Using eye height in different postures to scale the heights of objects.

Four experiments examined eye height (EH) scaling of object height across different postures. In Experiment 1, participants viewed rectangular targets while they were standing, seated, and prone. Standing and seated judgments were similar, possibly due to EH scaling. Prone judgments were significantly lower, a result not attributable to the unfamiliarity of that posture (Experiment 2). In Experiment 3, shifts of seated EH produced height overestimations equivalent to those of standing viewers. Experiment 4 examined the visual salience of size information in the seated and prone judgments by holding EH constant and manipulating another source: linear perspective. Participants viewed targets placed on true- and false-perspective (FP) gradients. The FP gradient affected prone judgments but not seated judgments, which presumably relied on EH. It appears that the human visual system weights size information differentially depending on its utility.