Visual Perception of Caught Weight
Pages 4

In the above studies observers made their judgments in comparison to "standards", that is, they occasionally viewed lifts for which they were told the weight. Gilden (1991) suggested that this leaves open the possibility that perception of this physical dynamic (lifted weight) is not a general phenomenon, i.e., that KSD is not a general perceptual principle. Bingham (1993) has argued that the use of standards is not necessary. In his work observers made judgments that were "roughly" as accurate as those made with standards.