How do we recognize objects? How do we reason about objects when they are absent and only in memory? How do we conceptualize the three dimensions of space? Do different people do these things in different ways? And where are these abilities located in the brain? During the past decade cognitive scientists have devised new experimental techniques; researchers in artificial intelligence have devised new ways of modeling cognitive processes on computers; neuropsychologists are testing new models of brain organization.. Many of these developments are represented in this collection of essays. The papers, though reporting work at the cutting edge of their fields, do not assume a highly technical background on the part of readers, and the volume begins with a tutorial introduction by the editor, making the book suitable for specialists and non-specialists alike.