Perceiving the size of trees: Biological form and the horizon ratio

Abstract

Physical constraints produce variations in the shapes of biological objects that correspond to their sizes. Bingham (in press-b) showed that two properties of tree form could be used to evaluate the height of trees. Observers judged simulated tree silhouettes of constant image size appearing on a ground texture gradient with a horizon. According to the horizon ratio hypothesis, the horizon can be used to judge object size because it intersects the image of an object at eye height. The present study was an investigation of whether the locus of the horizon might account for Bingham's previous results. Tree images were projected to a simulated eye height that was twice that used previously. Judgments were not halved, as predicted by the horizon ratio hypothesis. Next, the original results were replicated in viewing conditions that encouraged the use of the horizon ratio by including correct eye height, gaze level, and visual angles. The heights of cylinders were inaccurately judged when they appeared with horizon but without trees. Judgments were much more accurate when the cylinders also appeared in the context of trees.

Large errors, but no depth compression, in walked indications of exocentric extent

“…The most salient difference involves the fact that the walking task entails locomoting out to the stimulus location and stopping at two endpoints in succession, whereas the verbal task and the visualmatching task in Loomis et al (1992) do not. This methodological distinction can be characterized as creating task differences in terms of egocentric versus exocentric distance perception (e.g., Loomis et al, 1992;Loomis, Da Silva, Philbeck, & Fukusima, 1996), relative versus absolute distance perception (e.g., Franz et al, 2001;Vishton et al, 1999), and definite versus relative distance perception (e.g., Bingham, 1993;. Similar ideas have been expressed by a variety of other authors (Abrams & Landgraf, 1990;Brenner & Smeets, 1996;Gillam & Chambers, 1985;Mack et al, 1985;Marteniuk & Roy, 1972;Soechting & Flanders, 1992).…”

The role of eye height in perceiving affordances and object dimensions

“…Its role in apparent-size perception has been less clear. Studies manipulating EH in pictures have produced both strong (Rogers, 1996) and weak (Bingham, 1993) effects for judgments of relative object size. Empirical manipulations of EH in real scenes have also produced ambiguous results for judgments of absolute size (Stoper, 1990;Stoper & Bautista, 1992;Wraga & Neisser, 1995).…”

Allometry and Space Perception: Compression of Optical Ground Texture Yields Decreasing Ability to Resolve Differences in Spatial Scale

“…The paradigm was to present observers with displays consisting of three simulated trees appearing in the context of a simulated ground texture (see Figure 1). The simulations were generated as described in Bingham (1993aBingham ( , 1993b. Two of the trees appeared on the left and right sides of the display.…”

“…The idea is that the density of the optical ground texture made it difficult to resolve differences in distance. Image size was controlled in Bingham (1993aBingham ( , 1993b by holding it constant. Thus, larger trees were viewed at larger distance and the branching of the trees was also dense.…”

“…However, they did not investigate whether observers could judge body size. Bingham (1993aBingham ( , 1993b investigated whether the allometric form solution to the scaling problem would generalize to the traditional space perception problems of size and distance perception. He also investigated whether the solution would generalize to plants and in particular to trees.…”