Yeshurun, Y. & Carrasco, M. (1998). Attention improves or impairs visual
performance by enhancing spatial resolution. Nature, 396: 5 Nov.
Covert attention, the selective processing of visual information at a
given location in the absence of eye movements, improves performance in
several tasks, such as visual search and detection of luminance and vernier
targets[1-6]. An important unsettled issue is whether this improvement
is due to a reduction in noise (internal or external), a change in decisional
criteria[10,11],or signal enhancement[3,5,12]. Here we show that attention
can affect performance by signal enhancement. For a texture segregation
task in which performance is actually diminished when spatial resolution
is too high, we observed that attention improved performance at peripheral
locations where spatial resolution was too low, but impaired performance
at central locations where spatial resolution was too high[4-12]. The
counterintuitive impairment of performance that we found at the central
retinal locations appears to have only one possible explanation: attention
enhances spatial resolution.