Psyche 6(15): 'Perception, attention and the grand illusion' by Alva Noe and J. Kevin O'Regan
Patrick Wilken
PSYCHE: AN INTERDISCIPLINARY JOURNAL OF RESEARCH ON CONSCIOUSNESS
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PERCEPTION, ATTENTION AND THE GRAND ILLUSION
Alva Noe(1) & J. Kevin O'Regan(2)
(1) Department of Philosophy
UC Santa Cruz
Santa Cruz CA 95064
U.S.A.
an...@cats.ucsc.edu
http://www2.ucsc.edu/people/anoe/
(2) Laboratoire de Psychologie Expérimentale Centre National
de Recherche Scientifique
Université René Descartes
92774 Boulogne Billancourt
FRANCE
ore...@ext.jussieu.fr
http://nivea.psycho.univ-paris5.fr
Copyright (c) Alva Noe & J. Kevin O'Regan 2000
PSYCHE, 6(15), October 2000
http://psyche.cs.monash.edu.au/v6/psyche-6-15-noe.html
KEYWORDS: attention, inattentional blindness, perception, perceptual
consciousness, vision, visual experience, visual consciousness.
COMMENTARY ON: A. Mack and I. Rock. (1998) *Inattentional Blindness.*
MIT Press. 288 pp. ISBN: 0262632039. Price: $US 25 pbk.
ABSTRACT: This paper looks at two puzzles raised by the phenomenon of
inattentional blindness. First, how can we see at all if, in order to
see, we must first perceptually attend to that which we see? Second, if
attention is required for perception, why does it seem to us as if we
are perceptually aware of the whole detailed visual field when it is
quite clear that we do not attend to all that detail? We offer a general
framework for thinking about perception and perceptual consciousness
that addresses these questions and we propose, in addition, an informal
account of the relation between attention and consciousness. On this
view, perceptual awareness is a species of attention.
1. INTRODUCTION
If you focus your attention on a basketball game -- for example, on the
number of times the white team possesses the ball -- you will be
unlikely to notice the person in a gorilla-suit who walks across the
court (Simons & Chabris, 1999). This is an example of what Mack and Rock
(1998) call "inattentional blindness" (IB). This term calls to mind what
they take to be the central theoretical upshot of IB: that we only
perceive that to which we attend. This upshot gives rise to what we
shall call the paradox of perceptual attention: to see detail in the
environment, you must direct your attention to it. But how can you
direct your attention to an unperceived feature of the scene? Surely in
order to direct your attention, you must already perceive that to which
you wish to direct your attention. This paradox would seem to threaten
the very possibility of perceptual awareness.
This is not the only puzzle arising from the supposedly
attention-dependent nature of perception. It does not *seem* to us as if
we only see that to which we attend. It seems to us, rather, as if we
are perceptually aware of the densely detailed, stable and persistent
environment around us. But since we do not attend to all that detail, at
least not all at once, then it would seem to follow that perceptual
consciousness -- that feeling of awareness of all the detail -- is
misguided. Indeed, reasoning along these lines has led numerous writers
to argue that visual consciousness is a "grand illusion" (e.g.
Blackmore, Brelstaff, Nelson & Troscianko, 1995; Dennett, 1991, 1992,
1998; O'Regan, 1992; Rensink, O'Regan & Clark, 1997).
Our aim in this paper is to speak to both of these puzzles. It should be
clear that each is, in effect, a puzzle about the nature of perceptual
consciousness. What is perceptual consciousness and what is its relation
to attention? In what follows we offer a framework within which to
answer these questions.
2. A PRELIMINARY (AND OBVIOUS) SOLUTION TO THE PARADOX OF PERCEPTUAL
ATTENTION
Let us begin by noting that the theoretical upshot -- that we only
perceive that to which we attend -- appears to be in conflict with the
common sense observation that we perceive a good deal more than we
notice. Driving is an example of a visually-guided behavior which we
seem to be able to perform, at least sometimes, in the nearly complete
absence of attention. To give another informal and familiar example,
many of us have had the experience of noticing, all at once, that a bell
has been chiming, and indeed, that it is now chiming for, say, the third
time. Surely the fact that we are able to say, now, that the bell has
chimed three times indicates that we in some sense heard the bell before
we first attended to it.
This conflict between the theoretical upshot and common sense is,
however, more apparent than real. There can be no doubt that we are
sensitive to a great deal of perceptual information -- that we are, for
example, able to guide our behavior by the use of this information -- in
the absence of attention. (Indeed, Bridgeman and his colleagues, as well
as, others have shown that we can guide behavior with information that is
*inconsistent* with what is in attention. See Bridgeman, Lewis, Heit &
Nagle, 1979; Bridgeman, Kirch & Sperling, 1981; Bridgeman, Peery & Anand,
1997. See also Aglioti, DeSouza and Goodale, 1995; Daprati & Gentilucci
1997). So there is a sense in which one might say that we are
perceptually sensitive to features of the environment of which we are
unconscious. However, importantly, not all perceptual sensitivity is in
this way unconscious. We mark this distinction by reserving the terms
"perception," "seeing" and "visual experience" for conscious perception
alone.
Notice that once this distinction is in place -- between that to which
one is perceptually sensitive, and that which one perceives (of which
one is perceptually conscious) -- the paradox of perceptual attention is
near to being resolved. To experience detail, one must detect it. But to
detect it, there is no requirement that one experience it. We now
propose a more general framework within which to account for this
distinction.
3. PERCEPTUAL SENSITIVITY
Consider a simple phototactic device such as one of Braitenberg's
vehicles (Braitenberg, 1984). The imagined vehicle is equipped with two
light sensors positioned next to each other on the front of the wheeled
vehicle. The left sensor is linked to the right rear wheel driving
mechanism and the right sensor is linked to the left rear wheel driving
mechanism. As a result of this wiring, the vehicle will orient itself
toward light sources and move towards them. Such a simple mechanism can
track and hunt light sources.
Suppose there is a light source on the left. If the vehicle were to turn
in the direction of the light, then the light source would no longer be
on the left. What stimulation the system receives depends on what it
does and what the system does is affected by what stimulation it
receives. This vehicle is built in such a way to *embody*, as it were, a
set of rules of sensorimotor contingency.
Now consider a more complicated device such as a missile guidance system
(MGS). The MGS pursues an airplane by making use, let's say, of visual
information about the plane. The MGS is designed, let's say, to speed up
in response to the diminishing of the image of the airplane in its
camera and to maintain speed if the size of the image is growing.
Similarly, the MGS is capable of modifying its behavior depending on
whether the image of the plane shifts to the left or right, up or down.
For example, the system might be designed to shift to the left when the
image of the airplane shifts to the left in its viewfinder, thus
bringing the image of the plane back into the center. The MGS, we may
say, *has mastery of* the sensorimotor contingencies of airplane
tracking, that is, it is built in such a way as to exploit, in its
tracking activities, the interdependence between the availability of
sensory information and its motor behavior. The MGS is, in this sense,
*attuned* to the structure of sensorimotor contingencies. The MGS is
*perceptually coupled* with its environment.
We propose that perceptual systems in animals be thought of along the
lines of the simple mechanical systems described here. A visual
perceiver is familiar with (has mastery of) the ways in which visual
information presents itself as a function of movement of the perceiver
with respect to the environment. Movement towards an object causes an
expansion of the retinal projection. A flick of the eyes to the left
causes a displacement of projected items to the right. Owing to the
curvature of the retina, the retinal projection of a straight line is
deformed in a predictable manner as one directs one's eyes upward. There
are a vast array of such sensorimotor contingencies; to be a perceiver
is, *at least*, to be the master of these regularities. (See O'Regan and
Noe, in press, for more detailed exposition.)
Perceptual sensitivity, on the view advocated here, consists in the
ability to explore the environment in ways mediated by knowledge of the
patterns of sensorimotor contingency that govern perceptual modes of
exploration.
4. PERCEPTUAL EXPERIENCE
We have described what we can think of as the *ground* of perceptual
consciousness: the perceptual coupling of animal and environment that
consists in the animal's access to environmental detail thanks to its
mastery of the sensorimotor contingencies that govern the way it
explores the environment. We have called this perceptual sensitivity.
But for an animal to be *aware* of that to which it is perceptually
sensitive is for it not merely to be appropriately coupled perceptually,
but for it to integrate its coupling behavior with its broader
capacities for thought and rationally guided action. The driver who
fails to pay attention to what he or she is doing or to that to which he
or she is responding is still able to exercise mastery of the
sensorimotor contingencies needed to drive the car. When in addition the
driver is able to make use of information not only about that to which
he or she is perceptually sensitive, but also about the character of his
or her perceptual tracking of the environment, we say the driver is
*aware* of what he or she sees.
We thus propose a second level of perceptual capacity. First, there is
perceptually guided activity or perceptual coupling. This is basic
perceptual sensitivity. Second, there is the accessing of information
about that to which we are perceptually coupled for the purposes of
thought and action-guidance and also the accessing of information about
the nature of one's tracking activity itself. This is perceptual
awareness or perceptual consciousness.
5. ATTENTION AND IB
How does attention fit into our view? The precise role of attention in
perceptually guided activity has been the subject of much study (see,
for example, Pashler, 1998). What IB demonstrates is that you need
attention for seeing. This is exactly what our view predicts. For what
is seeing but access to and control over one's perceptual activity? But
what is the confident exercise of access to and control over perceptual
activity but the direction of attention to the activity? What we are
calling perceptual awareness, then, just is a form of attention.
Note that we do not identify attention and perceptual awareness. As Mack
and Rock observe, they cannot be one and the same, since it is possible
to direct one's attention to nonperceptual features (Mack & Rock, 1998,
ch. 11). Indeed, it seems crucial that attention can be directed not
only to future possibilities (anticipated events, for example), but also
to past events in memory, to current feelings or sensations, and to
parts of one's body that are out of view. Attention, in all these
domains, consists in access to and control over information. We propose,
then, that perceptual awareness is the application of this power of
access and control to one's perceptual engagement with the world.
Note that our account provides the resources to give substance to the
"obvious" resolution of the paradox of perceptual attention noted above
in Section 2. Perceptual sensitivity -- perceptual engagement with the
environment -- is the ground of perceptual awareness and attention and
so is the ground of visual experience or seeing. You cannot see without
perceptual coupling, but you can perceptually couple without seeing.
Mack and Rock's findings suggest, however, that much care would be
needed to fill in the details of the account we are proposing. Of
particular delicacy, for example, is their finding (reported on pages
18ff. and in chapters 5, 6 and 7) that there is less IB when the critical
stimulus is the subject's own name, or a smiley face, and (more
surprisingly) that there is no such decrease in IB for a close variant
of one's own name -- e.g. Jeck instead of Jack -- or for a sad face. Mack and
Rock rightly point out that such data on IB and salient stimuli would
seem to favor the *late selection theory* of attention (Deutsch &
Deutsch, 1963; van der Heijden, 1991) as opposed to an *early selection*
account such as that of Broadbent (1958) and Treisman (1969). For our
purposes, however, the central point to be underscored is that there is
nothing in these findings that threatens our sensorimotor contingency
account. You cannot see (that is, have conscious visual experience)
without attention. This is consistent with the fact that some stimuli
are better attractors of attention than other stimuli. Motion
transients, for example, are powerful attractors of attention. Mack and
Rock's findings on salience and IB suggest that *importance* and
*affective charge* are also strong attactors of attention. Just as we
can perceptually detect a change before we see it, so we can
perceptually detect an instance of our own name -- because it is an
instance of our own name -- before we consciously experience it.
6. THE GRAND ILLUSION
If, as the IB results seem to show, we only perceptually experience that
to which we attend (or, as we can now say, that of which we are aware),
then why does it seem to us as if we experience the whole scene before
us? Do we have to conclude that the experience of a rich visual world in
front of us is some kind of "grand illusion"? This is the second puzzle
mentioned at the outset.
Consider the following example. You hold a bottle in your hands and your
eyes are shut. You make finger-to-bottle contact at a number of isolated
points. It seems to you, however, that you have tactile experience of
the whole bottle. On the "detailed internal model approach" it would be
supposed that the brain builds up a model of the bottle as a whole on
the basis of information about the bottle contained in the points of
contact. This is an example of amodal completion, of perceiving
something you do not, strictly speaking, perceive. You seem perceptually
to experience something about which you do not have complete
information.
For another example, consider the perceptual experience of partially
occluded objects. When you see a cat through a picket fence, you take
yourself to perceive a cat, even though, if we imagine that the cat
stands still, you only really see strips of the cat's surface through
the slats of the fence. Crucially, there is a genuine sense in which you
*experience* or *perceive* and do not merely surmise the strictly unseen
portions of the cat. One's experienced relation to the unperceived
portion of the cat is not at all like one's relation to the hallway
outside one's door. The hallway is also felt to be present. But this
feeling of presence is nonperceptual. The sensorimotor contingency
theory offers an explanation for these phenomena. First, the perceiver
of the cat "knows," in a practical sense, that a step to the right will
produce new cat-surface. It is the knowledge that movement or alteration
of the sensory organ gives rise, in systematic and predictable ways, to
new sensory data that is that in which the sensory character of our
contact with the cat consists. Second, it is precisely the absence of
this sort of sensorimotor contingency in the case of the hallway outside
one's door, or the room behind one's head, that makes these latter
examples a 'thought presence' but not an 'experienced presence.'
Consider another example. If you blink, this causes a dramatic effect on
your retinal impression of things in front of you. Seeing, we argue,
depends on one's implicit knowledge that such dramatic affects occur
when you blink. On the other hand, blinking has no effect on your
feeling of the presence of the room behind the head. This goes a long
way to showing that the felt presence of the room behind the head is not
a *perceptual* presence. (N.B. People are normally unaware of the
perceptual consequences of blinking just as they lack conscious access
to a great many sensorimotor contingencies, e.g. the effects on sensory
stimuli of eye saccades. Knowledge of the multitude of sensorimotor
contingencies constituting perceptual activity is implicit and largely
unconscious.)
>From these considerations we see now that the sensorimotor theory
provides us with the resources to explain (or rather to explain away)
the so-called grand illusion hypothesis.
Consider the bottle example again. Although it is true that you
perceptually experience the whole bottle, notice that it is not true
that it seems to you as if you perceptually encounter each and every
part of the bottle's surface. What is true is that you take yourself to
have access to the whole bottle because the whole of it is there in your
hands.
Exactly similar points hold in the case of vision. Look around the room.
Reflect on what it is like to see. Does it seem to you as if you see
*all* the environmental detail in uniformly sharp focus, all at once,
now? Clearly not. To make out detail, we need to fixate, and when we
fixate, that which is now presented to us only peripherally is now
outside the range of clear focus. These points are familiar to
psychologists, but they are also, or so we argue, familiar (at least
implicitly) to normal perceivers. To be a normal perceiver is to be a
master of the ways in which we manipulate ourselves to get better looks,
better sniffs, and so on, of the clutter around us. This mastery shows
itself in the thoughtless automaticity with which we direct our gazes,
squint for better focus, pat our pockets in quest of glasses, and so on.
What *is* true is that we take ourselves *to have access* to
environmental detail, for we take ourselves to be, in the manner
described above, coupled or attuned perceptually with (or to) the
environment. The "feeling of the presence" of all the environmental
detail consists, as we have seen, in our practical knowledge that we
have access to it. Crucially, it not only seems to us as if we have
access. We *do* have access to the detail. True, we do not have access
to all that detail in what is "coming in now". But crucially, while it
does seem to us as if the detail is all there now, in the world, it is
*not* the case that it seems to us as if all that detail is represented
all at once in consciousness.
It is of course true that people are surprised by the results of
experiments on inattentional and change blindness. In addition, students
are apt to find astonishing familiar psychology demonstrations of their
inability to tell the color of an object held in peripheral vision. It
is sometimes suggested that this astonishment is evidence that we do
tend to think of our experience along the lines of the "details in the
head" conception. But there are other ways of explaining the
astonishment. On our view, vision is a complicated skill-based activity.
We tend to be unaware, when we are engaged in our perceptual lives, of
the complicated things we do when we see. Just as dancers, musicians, or
athletes are inattentive to the subtle modulations they undertake in the
conduct of their activity, so perceivers fail for the most part to
attend to the ways in which seeing depends on eye movements (as well as
on head and body movements). The surprise we feel in demonstrations such
as these is comparable to the surprise we feel when we discover how
difficult it is to perform a manual task such as typing or driving with
a splint on one's little finger. We are insensitive to the complexity of
the things we do when we do things.
We conclude, then, that there *is* no grand illusion. It is wrong to say
that perceptual experience is misleading or illusory (at least in the
respects relevant to the present discussion). (For related discussion of
this issue, see Noe, Pessoa & Thompson, 2000; Noe in press.)
7. CONCLUSION
In this paper we have proposed an account of the nature of perception
and perceptual consciousness that both predicts and explains the
phenomenon of IB. In addition, our model provides satisfying answers to
the two puzzles stated at the outset. *How can we see, if in order to
see we must attend to that which is not yet seen?* Our answer is that we
are perceptually sensitive to a great deal more than we are aware of.
*Why do we have the feeling of the immediate presence of environmental
detail despite the fact that we do not, at any given moment in time,
attend to any but a small fraction of that detail and also that we lack
a richly detailed internal model?* We offer an account of the feeling of
presence by analyzing it in terms of confident skill-based access to
detail. Further, we challenge the often repeated claim that the fact
that we have this feeling of contact even though there are no detailed
internal models in the head demonstrates that perceptual consciousness
is a grand illusion. It does not seem to us as if we have all the detail
in the head. It seems to us as if the detail is there, in the world,
where in fact it is (Pessoa, Thompson & Noe, 1998; Noe et al., 2000).
Finally, we propose to treat perceptual awareness as, in essence, the
application of attention to one's own perceptual engagement with the
environment.
ACKNOWLEDGEMENTS
We would like to express our thanks to Bruce Bridgeman for comments on
an earlier version of this paper and also to an anonymous referree. A.N.
gratefully acknowledges the support of faculty research funds provided
by the University of California, Santa Cruz.
REFERENCES
Aglioti S., DeSouza J. F., & Goodale M. A. (1995). Size-contrast
illusions deceive the eye but not the hand. *Current Biology, 5,*
679-685.
Blackmore, S. J., Brelstaff, G., Nelson, K., & Troscianko, T. (1995). Is
the richness of our visual world an illusion? Transsaccadic memory
for complex scences. *Perception, 24,* 1075-1081.
Braitenberg, V. (1984). *Vehicles: Experiments in synthetic psychology.*
Cambridge MA: The MIT Press.
Bridgeman, B., Lewis, S., Heit, G., & Nagle, M. (1979). Relation between
cognitive and motor-oriented systems of visual position perception.
*Journal of Experimental Psychology: Human Perception and
Performance, 5,* 692-700.
Bridgeman, B., Kirch, M., & Sperling, A. (1981). Segregation of
cognitive and motor aspects of visual function using induced motion.
*Perception & Psychophysics, 29,* 336-342.
Bridgeman, B., Peery, S., & Anand, S., (1997). Interaction of cognitive
and sensorimotor maps of visual space. *Perception & Psychophysics,
59,* 456-469.
Broadbent, D. E. (1958). *Perception and communication*. London:
Pergamon Press.
Daprati, E. & Gentilucci, M. (1997). Grasping an illusion.
*Neuropsychologia, 35,* 1577-82.
Dennett, D. C. (1991). *Consciousness explained.* Boston: Little Brown.
Dennett, D. C. (1992). "Filling in" versus finding out: a ubiquitous
confusion in cognitive science. In H. L. Pick, Jr., P. van den
Broek, & D. C. Knill (Eds), *Cognition: Conceptual and
Methodological Issues* (pp. 33-49). Washington D. C.: American
Psychological Association.
Dennett, D. C. (1998). No bridge over the stream of consciousness.
*Behavioral and Brain Sciences, 21(6),* 753-754.
Deutsch, J., and Deutsch, D. (1963). Attention: some theoretical
consideration. *Psychological Review, 87,* 272-300.
Mack, A. & Rock, I. (1998). *Inattentional blindness*. Cambridge, MA:
The MIT Press.
Noe, A. (in press). Experience and the active mind. *Synthese*.
Noe, A., Pessoa, L., & Thompson, E. (2000). What does change blindness
really teach us about vision? *Visual Cognition, 7(1-3),* 93-106.
O'Regan, J. K. (1992). Solving the "real" mysteries of visual
perception: the world as an outside memory. *Canadian Journal of
Psychology, 46,* 461-488.
O'Regan, J. K. & Noe, A. (in press) A sensorimotor account of vision and
visual consciousness. *Behavioral and Brain Sciences.*
Pashler, H. (1998). *Attention.* Hove, U.K.: Psychology Press/Erlbaum.
Pessoa, L., Thompson, E. & Noe, A. (1998). Finding out about filling in:
a guide to perceptual completion for visual science and the
philosophy of perception. *Behavioral and Brain Sciences, 21(6),*
723-802.
Rensink, R. A., O'Regan, J. K. & Clark, J. J. (1997). To see or not to
see: the need for attention to perceive changes in scenes.
*Psychological Science, 8(5),* 368-373.
Simons, D. J. & Chabris, C. F. (1999). Gorillas in our midst:
sustained inattentional blindness for dynamic events. *Perception,
28(9),* 1059-1074.
Treisman, A. (1969). Strategies and models of selective attention.
*Psychological Review, 76,* 282-299.
van der Heijden, A. H. C. (1991). *Selective Attention in vision.* New
York: Routledge.
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Patrick Wilken http://www.csse.monash.edu.au/~patrickw
Editor: PSYCHE: An International Journal of Research on Consciousness
Board Member: The Association for the Scientific Study of Consciousness
http://psyche.cs.monash.edu.au/ http://assc.caltech.edu/