Recent studies on the different modes of attentional selection
have suggested that feature-based attention may be mediated by spatial
location. Here we provide evidence that supports this idea, and we investigate a possible time course for such mediation. We designed psychophysical
tasks to study whether a shift in spatial attention gives rise to a shift
in feature-based attention towards the features present at the attended
location. In one experiment, subjects looked at a central square that
disappeared 200 ms after trial onset. After a gap of 200 ms,
a peripheral square appeared 17 deg to the right or left of fixation
and acted to capture spatial attention. The peripheral square was extinguished 150 ms later, after which a second foveal square appeared for 50 - 150 ms. Subjects maintained fixation and compared the
colours of the two foveal squares regardless of the colour of the peripheral
one. We found that the colour of the peripheral square influenced colour
perception at fixation, with the effect being strongest approximately
100 ms after the onset of the final
foveal square. When the peripheral square was replaced with a parafoveal
ring to avoid any explicit summoning of spatial attention, no similar
effect seemed to occur.
© 2002 Pion Ltd