T he study of attention had a prominent place at the birth of psychology as a scientic discipline. Wundt devoted the rst chapter of his Einfuhrung in die Psychologie (Introduction to Psychology) to attention. He commented, for example,
If we practise letting our attention wander over the different parts of the eld of vision while keeping the same xation-point, it will soon become clear to us that the xation-point of attention and the xation-point of the eld of vision are by no means identical. (1912/1973, p. 20)
It has been recognized that at least two forms of spatial attention can be found in vision. For example, Wundt (1902) observed that attention could be involuntary or voluntary. A variety of distinctions have been made that more or less correspond to Wundt’s distinction, including goal-directed attention versus stimulus-driven capture and endogenous attention versus exogenous attention. The terms used to label these forms of attention are not important. The critical question is whether these two forms of attention involve the same or different mechanisms, and, if they involve different mechanisms, what are those mechanisms?