Effect of eccentricity on the relationship between detection and identification.

The relationship between the ability to detect a low-contrast grating and to identify its spatial frequency or orientation was examined at eccentricities ranging from 0 to 17.5 deg. The form of the relationship between the ability to detect and to identify stimuli as contrast varies was found to be the same for peripheral viewing as for central viewing, i.e., proportionality. Individual variations were seen in the effect of eccentricity on the identification/detection (I/D) performance ratio for a given discrimination. However, the composite data show no effect of eccentricity on the I/D ratio when low-frequency stimuli are used. With high-frequency stimuli, the I/D ratio decreases at large eccentricities. The results support the hypothesis that the primary difference between central and peripheral vision is the scale at which visual information is represented. In particular, the results suggest no change in the bandwidths of tuned mechanisms with respect to spatial frequency and orientation.