Dissecting Visual Attention
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Dissecting Spatial Visual Attention
William Prinzmetal
Ayelet Landau
University of California, Berkeley
Corresponding Information:
William Prinzmetal
E mail: wprinz@berkeley.edu
Department of Psychology
University of California, Berkeley 94720
USDissecting Visual Attention
I. Introduction and Background
The study of attention had a prominent place at the birth of psychology as a
scientific discipline. Wundt devoted the first chapter of his Einfuhrung in die
Psychologie (Introduction to Psychology) to attention. Wundt commented, for
example, “If we practise letting our attention wander over the different parts of the
field of vision while keeping the same fixation-point, it will soon become clear to
us that the fixation-point of attention and the fixation-point of the field of vision
are by no means identical” (p. 20, 1912/1973).
It has been recognized that there are at least two forms of spatial attention in
vision. For example, Wundt (1902) commented 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 vs.
stimulus-driven capture and endogenous attention vs. exogenous attention. The
terms that are 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? Modern investigators have largely been unclear whether voluntary
and involuntary attention are mediated by different mechanisms, or whether they
are simply different means of controlling a single mechanism. Rather, mostcontemporary investigations have focused on the properties of different methods of
summoning attention. The assumption is often made that involuntary attention has
the same effect on perceptual processes as voluntary attention (Rauschenberger,
2003) and that they effect the same neural mechanisms (Gazzaniga, Ivry, &
Mangun, 1998).
The research reported here challenges this assumption. Three separate
behavioral paradigms demonstrate that voluntary and involuntary attention have
different consequences. Furthermore, neural imaging (Esterman, Prinzmetal,
DeGutis, Landau, Hazeltine, Verstynen, & Robertson, under review) and EEG
studies (Landau, Esterman, Robertson, & Prinzmetal, under review) demonstrate
that they involve different neural mechanisms. Voluntary attention enhances the
perceptual representation so that the observer has a more veridical perceptual
representation of stimuli in an attended location than in an unattended location
(e.g., Lu & Dosher, 1998; Prinzmetal, 2005). Involuntary attention, on the other
hand, does not enhance the perceptual representation, but rather works on a non-
perceptual priming mechanism that only affects response time.
Although we are interested in the distinction between voluntary and
involuntary attention in a variety of paradigms, an excellent way of separating
voluntary and involuntary spatial attention is vision is the spatial cueing paradigm
developed by Posner and his colleagues (Posner, 1980).In the spatial cueing paradigm, subjects engage in either a simple target
detection or target identification task. Before the target appears, a location is
“cued” with, for example, a box changing color or brightening. A version of this
paradigm is illustrated in Figure 1.Insert Figure 1 about here
In this version, the task was to indicate which of two target faces was
presented by pressing a button. The cue consists of one of the boxes getting thicker
and turning red (dashed line in the figure). There are two kinds of trials. On valid
trials, the cue indicates the target location. On invalid trials, it indicates a nontarget
location. Eye movements are always monitored. Subjects are trained to not move
their eyes and trials on which eye movements are made are eliminated from the
analysis. The general idea is that subjects will “attend” to the cued location and
that target detection or identification will be better on valid trials than on invalid
trials.
Posner and his colleagues (e.g., Posner, Snyder, & Davidson, 1980) had
subjects engage in various detection and identification tasks. The onset of the cue
preceded the onset of the target by 1 second, and the cue was always informative
of the target location. For example, 75% of the trials were valid, and 25% were
invalid. Subjects were faster on valid trials than invalid trials in both detection and
