ABSTRACT
The research described in this chapter concerns the role of reference frames in perceiving the shape and orientation of objects. Ultimately, I describe some experiments I have done to understand how the human visual system might define these reference frames, but before I do this, I want to motivate the problem with some theoretical background concerning why one would postulate perceptual reference frames in the first place. Perhaps the easiest way to do this is to present reference frames as one possible solution to the problem of shape equivalence and then to describe some evidence that favors this hypothesis. Finally, I describe my own research testing three theories of how reference frames are selected.
