Temporal properties of human visual filters: number, shapes and spatial covariation.

The temporal properties of the foveal visual filters were revealed using a method which is a variant on previously used noise masking paradigms. This enables the temporal properties of the mechanisms underlying threshold detection of a spatio-temporal probe to be measured. In accord with recent suggestions these results support the existence of three temporal mechanisms. The evidence for the third, higher temporal mechanism is only persuasive at low spatial frequencies. Furthermore, the results suggest that although there is some degree of spatio-temporal covariation in the filtering properties either of individual filters or across the filter population, the well known spatio-temporal covariation in human detection sensitivity is adequately explained by a sensitivity scaling of individual temporal filters with approximately invariant temporal properties.