Search

This study is the first to investigate: (a) 'temporal performance fields,' whether the speed of information accrual differs for different locations at a fixed eccentricity, and (b) whether covert attention modulates temporal dynamics differentially at isoeccentric locations. Using the speed accuracy tradeoff (SAT) procedure, we derived conjoint measures of how isoeccentric locations and precueing targets location affect speed and accuracy in a search task. The results demonstrate the existence of temporal performance fields, analogous to spatial performance fields: information accrual was fastest for target on the horizontal meridian, intermediate for targets at the intercardinal locations, slow for targets on the vertical meridian, and slowest for targets at the North (N) location (accrual time pattern: E&WS>intercardinal>E&W). Hence, the compensatory effect of attention eliminated the temporal asymmetries across isoeccentric locations.

The visual system has a duplex design to meet conflicting environmental demands: the fovea has the resolution required to process fine spatial information, but the periphery is more sensitive to temporal properties. To investigate whether the periphery's sensitivity is partly due to the speed with which information is processed, we measured the full timecourse of visual information processing by deriving joint measures of discriminability and speed, and found that speed of information processing varies with eccentricity: processing was faster when same-size stimuli appeared at 9 degrees than 4 degrees eccentricity, and this difference was attenuated when the 9 degrees stimuli were magnified to equate cortical representation size. At the same eccentricity, larger stimuli are processed more slowly. These temporal differences are greater than expected from neurophysiological constraints.