Abstract: Prior experiments on shape constancy from novel views are inconclusive: some show that shapes of objects can be recognized reliably from novel views, while others show just the opposite. Our analysis of prior results suggests that shape constancy from novel views is reliable when the object has properties which constrain its shape: the object has volumetric primitives, surfaces, it is symmetrical, it is composed of geons, its contours are planar, its images provide useful topological information about its 3D structure. To test the role of some of these constraints we performed a set of experiments. Solid shapes (polyhedra) were shown on a computer monitor by means of Kinetic Depth Effect. Experiment 1 showed that shape constancy can be reliably achieved when a polyhedron is represented by its contours (most of the constraints are present), but not when it is represented by vertices or by a polygonal line connecting the vertices in a random order (all the constraints are absent). Experiments 2 and 3 tested the role of individual constraints. Results of these experiments show that shape constancy from novel views is reliable when the object has planar contours, and when the shapes of the contours together with topological information about the relations among the contours allow for unique interpretation of the shape. Symmetry of the object and the topological stability of its image also contribute to shape constancy.
This page attempts to reproduce the experimental procedure used in (Pizlo & Stevenson, 1999). It uses a Java 1.1-based Applet, which should run in Netscape 4.6 or later, Internet Explorer 4.0 or later, Mozilla, Konqueror, and Opera (the last three would probably require a plug-in). This software has been tested on Linux, Windows, and MacOS X.
Please wait for the applet to load. After loading, it should do an automatic performance calibration. To run an experiment, select the number of trials that you would like, pick a stimulus type, and click on "OK".
Pizlo, Z. & Stevenson, A. (1999) "Shape constancy from novel
views". Perception & Psychophysics 61, 1299-1307.
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