Evidence of spatial and temporal channels in the correlational structure of human spatiotemporal contrast sensitivity.

1. The statistical correlation of detection thresholds for pairs of stimuli should be higher for stimuli detected by the same mechanism than for stimuli detected by different mechanisms--a property that can be used to probe the visual mechanisms that underlie detection. 2. Correlation of contrast sensitivities for pairs of spatiotemporal stimuli is approximately a linear function of spatial or temporal frequency separation in octaves. Using the slope of this function as an index of neural processing gave results consistent with: more spatial mechanisms than temporal; more spatial mechanisms at low temporal frequencies than at high; and at least two temporal mechanisms active at spatial frequencies up to 22.6 cycles deg-1. 3. This method of analysing sensitivity data is insensitive to experimental conditions and applicable to any sensory detection task mediated by tuned channels. In addition to being applicable to psychophysical sensitivity measurements, it may also be useful in analysing some kinds of electrophysiological measurements that pool the responses from many active mechanisms (such as evoked potentials).