How do we recognize objects despite differences in their retinal projections when they are
seen at different orientations? Marr and Nishihara (1978) proposed that shapes are
represented in memory as structural descriptions in object-centered coordinate systems, so
that an object is represented identically regardless of its orientation. An alternative
hypothesis is that an object is represented in memory in a single representation
corresponding to a canonical orientation, and a mental rotation operation transforms an …