Fast Perceptual Learning in Visual Hyperacuity

Tomaso Poggio, Manfred Fahle, Shimon Edelman


In many different spatial discrimination tasks, such as in determining the sign of the offset in a vernier stimulus, the human visual system exhibits hyperacuity by evaluating spatial relations with the precision of a fraction of a photoreceptor's diameter. It is proposed that this impressive performance depends in part on a fast learning process that uses relatively few examples and that occurs at an early processing stage in the visual pathway. This hypothesis is given support by the demonstration that it is possible to synthesize, from a small number of examples of a given task, a simple network that attains the required performance level. Psychophysical experiments agree with some of the key predictions of the model. In particular, fast stimulusspecific learning is found to take place in the human visual system, and this learning does not transfer between two slightly different hyperacuity tasks.