Attention Seeing and Change Blindness

8/10/2019 Attention Seeing and Change Blindness

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Forthcoming in Philosophical Issues

Attention, Seeing, and Change Blindness

Here are two crowds of balls (from Dretske 2010):

View crowd A first and then view crowd B, each for a second or two. If you are like

most people, you will fail to notice any difference in the crowds. But there is a dif-

ference: crowd A has one more ball. This is an example of change blindness. Do you

see the ball that is the difference in the two crowds? You fail to see thatthere is a

difference in the two crowds, but do you see the extra ball?

The question is significant for three reasons. First, reflection upon it enables

us to understand better the character or texture of visual experience. Secondly (andrelatedly), how we answer the question is tied up with how we handle the further

vexing question of the nature of attention and its relationship to consciousness. Fi-

nally, what we say about this case (and others like it) is relevant to how we think

about the vehicles of consciousness awareness the conscious states in our headsthat are directed at things outside us.

My discussion is divided into eight parts. I begin with a discussion of seeing

and visual consciousness. In Section 2, I relate this discussion to the crowd of balls

example and the issue of change blindness. I argue that the view Fred Dretske takes

of this case (and others like it) is mistaken. Section 3 takes up the topic of levels of

representation involved in visual awareness. I distinguish here two different gener-

al hypotheses with respect to change blindness the comparison failure hypothesis

and the representational failure hypothesis and I adjudicate between them. Thenext three sections are concerned with various aspects of attention and the relation-

ship of attention to seeing. Section 7 turns to the nature of the vehicles of conscious

awareness. The final section addresses the general question of whether we see all

the things in the field of view that are large enough to see. It is suggested that on


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one reading of this question we do but that on another reading we often fail to see

things in plain view that are large enough for us to see.

1. What is seeing?

In ordinary English, we use the term see both with respect to objects and with re-spect to facts. We talk of seeing tables, chairs, trees, stars and people, for example.

We also describe one another as seeing that the table is covered with books, that the

chair is made of wood, that the tree has acorns on it, and so on. Chisholm (1957),

Drestke (1969) and Jackson (1977), among others, have argued that there is a ge-

nuine distinction reflected in our talk here: seeing things is not reducible to seeing

that things are thus-and-so. We see things andwe see facts.

That there really is a difference between thing seeing and fact seeing is illu-

strated by cases such as the following: suppose that a white cube is bathed in red

light. It looks red to Paul, who is viewing it. Paul cannot see that the cube is red; for

the cube is white. Perhaps the cube also looks straight ahead when in reality it is offto the right and Paul is seeing it in a mirror placed at a forty-five degree orientation

in front of Paul. Perhaps, the cube looks irregular in its shape in virtue of an appar-

ent shape distortion brought about by the mirror. Paul does not see that the cube is

off to the right; not does he see that the object he is viewing has a cubical shape.

Still, Paul does see the cube.

The general point here is that one can see an object Owithout there being

any property, P, such that one sees that Ohas Por without there being any property,

P, such that one sees with respect to Othat it has P. This is indicated by the cube ex-

ample and other such cases of ubiquitous error.

So, not all seeing is seeing that. But what is it to see a thing? In the pheno-menal sense of the term see, one sees a thing just in case ones visual experiencemakes one visually conscious of it. Arguably, see has other senses too. Zombie

replicas of human beings are conceptually possible, according to many philosophers,

and it does not seem clearly wrong to say that they see things even though they un-

dergo no experiences. Take also the case of a simple surveillance robot pro-

grammed to detect activity in a yard. A thief might be intent on getting across the

yard without being seen by the surveillance robot. In being so intent, the man is not

committed to supposing that the robot has experiences. He simply assumes that if

he is registered or detected by the robot eyes then he is seen and the game is up. In

this sense of see, blindsight subjects may be said to see the items in their blind

fields, since they evidently do detect or register some stimuli there, as witnessed bytheir correct guesses about those stimuli.1

11 People with blindsight have large blind areas or scotoma in their visual fields, due

to brain damage in the post-geniculate region (typically the occipital cortex), and

yet, under certain circumstances, they can issue accurate statements with respect to

the contents of those areas. See Weiskrantz 1986. For example, in forced choice

tests, blindsight subjects can make accurate guesses with respect to such things as


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When I use the term see I shall be using it with its phenomenal sense. My

concern thus will be with what might be called conscious seeing. It is evident thatneither the blindsight subject, nor the surveillance robot nor the zombie consciously

see anything.

If we suppose that seeing a thing is a matter of undergoing a visual expe-

rience that makes one conscious of that thing, we must now face the question ofwhat is involved in being conscious of a thing. Evidently, I can be conscious of a

thing without being able to identify the thing, as the cube example above shows.

Think too of being conscious of a thing located on the other side of thick, distorting

darkened glass. I might be able to see the thing and track its movements without

having the faintest idea what it is.

Still even if I cant identify a thing, if I am conscious of it then it must bemarked out or differentiated in the phenomenology of my experience. For suppose

that it is not. Then I wont even be able to mentally point to the thing on the basis ofmy experience. So, my experience alone does not enable me even so much as to

wonder What is that? with respect to the thing. Nor, does my experience aloneenable me directly to form beliefs or make judgments about the thing. The thing

thus is hidden from me. I am blind to it. I am not conscious of the relevant thing.

So when am I conscious of a thing? The above remarks suggest the following

test: I am conscious of a thing just in case my experience has a phenomenal charac-

ter directlyon the basis of which I can at least ask myself Whats that? with respectto the thing (or form some singular belief about it).2

Here is another way to motivate the above test. Consider a perfectly camouf-

laged moth on a tree trunk. The moth is in plain view. Do I see it? What about the

blob of white-out on the page of white paper? I have no idea where it is on the pa-

per, as I hold the page before me. Do I see it?

presence, position, orientation, and movement of visual stimuli. They can also guess

correctly as to whether an X is present or an O. Some blindsight patients can even

issue accurate guesses with respect to colors in the blind field.2This test, as stated, oversimplifies minimally. Suppose, for example, you put your

head around the door of my office and ask me if Id like to go to lunch. I see your

head. Do I also see you? Intuitively I do. Cases like this can be handled either by

modifying the test so that the demonstrative is permitted to pick out some suffi-

ciently large or salient part of the relevant thing or by arguing that the demonstra-

tive can be applied directly to the thing even though only part of it is in the field of

view. Either way, it is admitted that there is a context-dependent dimension to see-ing things.

As for the case of simple creatures without the capacity to form propositional

attitudes, I deny that they see things around them (in the relevant sense of see). Ido not deny, of course, that such creatures may register or detect things in their en-

vironments and thus see them in a weaker sense. (Those who are not as liberal in

the ascription of propositional attitudes as I may wish to hold instead that the test,

as proposed, is only for creatures capable of forming beliefs, etc.)


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It seems to me that the natural, intuitive view to take is that I am not con-

scious of either the perfectly camouflaged moth or the blob of white-out. But why

not? In the moth case, surely I am not conscious of the moth because my visual ex-

perience is not aboutthe moth at all. The moth is not a component or constituent of

the content of my visual experience.

It might be replied that this is mere prejudice. My experience isabout themoth. But then how does my experience latch onto the moth? After all, the moth is

not marked out or differentiated in the phenomenology of my experience. I cannot

mentally point to it. So, I cant even ask myself Whats that? with respect to themoth directly on the basis of my experience. Surely, the right thing to say is that I

am notconscious of the moth.

Not everyone will be convinced. Suppose that the moth covers a bright pur-

ple postage stamp stuck to the tree trunk. The moth blocks my view of the postage

stamp. But if the moth blocks my view, I must see it.

This is too fast. In general, the presence of a blocker with respect to a per-

ceptual experience does not license the conclusion that the blocker is perceptuallyexperienced. The earplugs I am wearing block my hearing the sound my alarm clock

is emitting. But I dont hear the earplugs. The taste paste I have smeared on mytongue prevents me from tasting the chocolate I am eating but I do not (or need not)

taste the taste paste.

Of course, in denying that the moth is seen, I am not denying that light re-

flected from the moth carries information that reaches the eyes. My claim is that the

moth is not seen in the phenomenal sense of the term see. There is no consciousorphenomenalrepresentation of the moth.

But what if there are three different moths hidden on the tree trunk? Again

my view is that there is no moth that I see. Of course, if there are lots of moths andthey line up perfectly with one another so that they cover the entire tree trunk, then

I do see a blanket of moths though I misidentify the thing I am seeing as a tree trunk.

Still even in this case I fail to see individual moths.3

Here is one more example. Fixate your eyes upon the plus sign in the middle

of the figure below.

3What if I decide to focus on a particular unmarked-out region of the tree trunk that

(as it happens) is filled by a perfectly camouflaged moth? Still, in my view, I do not

see the moth; for the moth is not differentiated in the phenomenology of my expe-

rience. If I ask myself Whats that? with respect to the region I am focusing upon,

there is nothing in the phenomenal character of my visual experience itself that di-

rectly enables me to apply the demonstrative concept.


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You certainly see each bar on the left. What about each bar on the right? If you

think you see each such bar, tell me how many bars there are on the right without

moving your fixation point. You wont be able to do it (as you can with the bars on

the left). Why not? Surely because it is not the case that each bar on the right is

clearly marked out or differentiated in the phenomenology of your experience. But

then surely even though you are conscious of the bars on the right, it is not true that

you are conscious of each individual bar.

This is the result delivered by my earlier proposal. You see the bars you arevisually conscious of themsince the phenomenal character of your visual expe-

rience, as you stare at the central dot, directly enables you to ask with respect to the

bars collectively Are theyparallel? (for example). But consider the sixth bar away

from the plus sign on the right. As you fixate on the plus sign, you cannot mentally

point to it. You cannot apply the concept that barto it directly on the basis of the

phenomenal character of your experience (without changing your fixation point).

So, you do not see it.

Ned Block has objected to me that the case of the bars exposes my test for

seeing a thing as ad hoc. For while it is true that the phenomenal character of ones

experience does not enable one to attend to the sixth bar in the middle of the groupof bars on the right of the plus sign if one keeps ones eyes fixated on the plus sign, it

does enable one to do this, if one moves one's eyes appropriately. According to

Block, my choosing the former as what matters to seeing the sixth bar rather than

the latter is ad hoc.

I disagree. In actual fact, by hypothesis oneseyes are fixed on the plus sign.

Given the actual fixation point for ones eyes, onesexperience has a certain pheno-

menal character. Thatphenomenal character does not enable one to demonstrate

the sixth bar. So, one is not conscious of that bar. One does not see it. Of course, if

one moves ones eyes appropriately so that onesfixation point changes to the sixth

bar, say, the phenomenal character of the experience one thenwould have wouldenable one to attend to the fifth bar. But thatphenomenal character is not the same

as the phenomenal character of ones actualexperience obtained with oneseyes

fixed on the plus sign.

Perhaps it will be replied that there is an alternative reading of the claim that

the phenomenal character of onesexperience enables one to demonstrate the sixthbar if one move oneseyes which I am ignoring, namely that the phenomenal charac-

ter of ones actual experience, obtained with oneseyes fixated on the plus sign, is


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such that it enables one to demonstrate the sixth bar, if one moves ones eyes. Given

this reading, the objector may say, it remains ad hoc to suppose that what matters to

the question of whether one sees the sixth bar is whether the phenomenal character

of onesexperience, obtained with oneseyes fixated on the plus sign, is such that ifone keeps oneseyes fixated on the plus sign, it enables one to demonstrate the sixth

bar.Again, I disagree. Consider the claim that my current state of fitness enables

me to run a mile in 6 minutes. What do I mean? That my current state of fitness is

such that if I go on a super-intensive training schedule, it enables me to run a mile in

6 minutes? Or that my current state of fitness, as things are, enables me to run a

mile on 6 minutes? Obviously the latter. On the former reading, it might be true of

someone who was grossly overweight that their current state of fitness enabled

them to run a mile in 6 minutes. That would be a perverse (and ad hoc) interpreta-

tion of what is being asserted. Correspondingly, given that ones eyes are fixated onthe plus sign, the right reading of the claim that the phenomenal character of ones

experience enables one to demonstrate the sixth bar is that that phenomenal cha-

racter enables one to demonstrate the sixth bar, if one keep ones eyes on the plussign. And so understood, the claim is false.

My claims about seeing and visual consciousness have counterparts else-

where. You can weigh the marbles (by placing them on the scale), but you need not

thereby weigh one of the marbles in particular (you may have no idea how much it

weighs). You can think about your colleagues for example, you can think of your

colleagues that they get along well together without thereby thinking of any col-league in particular. Likewise, I claim, you can see the bars without seeing the fifth

bar in particular. See, like weigh and think of, hasa collective or non-distributive

character.

I should add that in saying that, with eyes fixated on the plus sign, you do not

see the sixth bar, I am not denying that it contributes to the phenomenology; for had

it been missing or had it been red in color, the phenomenology would undoubtedly

have been different. Equally though had the camouflaged moth been blue or spot-

ted, say, the phenomenology would have been different. Still in actual fact the moth

is not seen. To take a different sort of case, suppose that the falling rocks dent the

car roof. It can be true that if the only rock weighing 4 pounds, say, had not been

present, the rocks would not have dented the car roof, and thus that the 4 pound

rock contributed to the denting, even though that rock individually did not dent the

car roof.4

4Here is a further reason to deny that the sixth bar is seen. Fixate on the bars and

point a finger so that its tip is touching the sixth bar. Now move your eyes and hold

them fixed on the central plus sign. Nothing in the phenomenology of your expe-

rience will inform you that the finger is touching a bar as opposed to one of the gaps

between bars. But if the location of the sixth bar is marked out in the phenomenolo-

gy of your experience, equally the location of the finger should be. How then could

the phenomenology leave open whether the finger is touching a bar? The obvious


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Still, dont you know that the sixthbar away on the right that particular bar

-- is black on the basis of your experience (Dretske 2010)? If so, surely you do see it

after all. To this I reply that via your experience you know that the bars on the right

collectively are black and so you are in a position to infera priori that each particu-

lar bar is black. But you dont know that the sixthbar away is black directlyon the

basis of the phenomenal character of your experience. Your cognitive attitudesabout the sixth bar in particular arent formed directly in this way. So, you do not

see the sixth bar away.

Suppose now that the bars are real three-dimensional objects instead of pic-

ture bars and suppose further that behind one of the black bars is a thinner red bar.

Since you cant tell from your viewpoint whether there is a concealed red bar, you

dont have the collective knowledge that allthe bars on the right are black. So, it

may be said, your knowledge that the sixth visible bar away is black cannot derive

from your collective knowledge that all the bars on the right are black.

To this I say the mere possibility of there being a red bar behind one of the

black bars does not undermine your claim to have the collective knowledge that allthe bars are black (any more than various skeptical scenarios undermine ordinary

claims to knowledge). Still suppose that in actual fact there is such a red bar. In that

event, what you know via your experience that all the non-occludedbars on the right

all the bars on the right in plain view -- are black. You also know via your expe-

rience that you are seeing more than six bars on the right. So, you are in a position

to infer that the sixth non-occluded bar away is black. Your knowledge here is indi-

rect. You dont see the sixth non-occluded bar away.

2. The crowds of balls

Crowd A has one more ball than crowd B. You dont notice any difference.Do you see the extra ball in crowd A the ball that is the difference? To make

headway with this question, consider first the famous Seurat picture below and fix-

ate your eyes on the little girl holding some flowers in the middle of the picture.

conclusion to draw is that the location of the sixth bar is not marked out in the phe-

nomenology: you do not see the sixth bar.

This is also supported by the following observation. Fixate on the sixth bar in

and then switch your fixation point to the plus sign. You will find that the sixth bar

effectively disappears as a discrete entity in your experience.


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I predict that, as you do so, you will be unable to attend to the pipe the reclining man

on the left is smoking. For you, it will be as if the pipe is not there and likewise for

the qualities of the pipe, for example, its shape. Being unable to attend to these

things, as you fixate on the little girl, they are hidden from you. You are blind to

them. They are not marked out in the phenomenology of your experience. The

same is true for the fifth vertical bar away from the plus sign in the following figureas your eyes track down from the top black spots to the lower black spots.

Note however that this is not the case if your eyes take a different path from the plus

sign on the left to the plus signs just below the bars. Here towards the end of the

tracking, each and every bar is clearly marked out in the phenomenology of your

experience. You see each bar.

The point these cases illustrate is that, in general, shifting the fixation point

of your eyes changes the phenomenology of your experience somewhat. With a shift

in eye fixation, you can see things you did not see before.

Returning now to the two crowds, do you see Bill (ball # 43) the extra ball

in crowd A? My answer is that if you view crowd A briefly, you may well not see Bill.

It depends upon how your eyes move. Bill may well be like one of the middle bars in

the group of bars to the right of the plus sign as your eyes move down from the up-

per black spot to the lower ones. In that case, Bill is onlypotentiallyseen: Bill is such

that you would have seen it, if your eyes movements had been suitably different.


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Of course, you would also have seen Bill if it had been black instead of grey.

The difference in color between Bill and the other balls would have drawn your at-

tention to Bill just as it would to the fifth bar if it were painted red. But then your

eye movements would have been different as would the phenomenology of your ex-

perience.

One philosopher who takes an opposing view of this case is Fred Dretske

(2010). According to Dretske, you do see Bill. He argues as follows:

(1) If S directly sees (and thereby knows) that x is F, then S sees (is consciousof) x.

(2) People know that Bill (ball #43) is grey by directly seeing that Bill is grey.

So,

(3) People see Bill.

The contentious premise here is (2). Given their actual eye movements, people may

well notdirectly see that Bill is grey. I grant that people see all the non-occluded

balls (in the collective sense of all). So, I am happy to concede that people see thatthe non-occluded balls are grey directly on the basis of their experience. However,

seeing all the non-occluded balls and seeing that all the non-occluded balls are greyis compatible with not seeing Bill. If people dont see Bill, they dont directly seethat Bill is grey. Rather people see that Bill is grey by inferring that ball #43 Bill

is grey from their knowledge that all the non-occluded balls are grey.

Again: if Bill had been black, people would have spotted it and then seen di-

rectly that Bill is black. But, to repeat, their eye movements and experiences would

then have been different. They would have seen a thing they actually may well fail

to see.

If a difference in color of ball #43 would have been spotted right away, must

not people see ball #43? No. What people would have seen is not a reliable indica-

tor of what they actually see. If the perfectly camouflaged moth had been red,people would have seen it on the tree trunk. But it does not follow that people ac-

tually see it. Further, I do not wish to deny that information about each ball and its

color may be represented by the visual system. It is to this topic and its relevance to

change blindness that I turn next.

3. Levels of representation


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Evidence that a rich visual representation is generated in viewing a scene

with multiple things in it is provided by an experiment performed by Lamme and

Landman (2003). In this experiment, subjects were presented with three different

scenarios, as shown in the figure below:

In the top scenario, cuing occurs with the presentation of the second scene and sub-

jects are then asked whether the cued item has changed or not. In the middle scena-

rio, cuing occurs with the presentation of the first scene. In the bottom scenario,

cuing occurs after the disappearance of the first scene but before the presentation of

the changed scene. For the middle and bottom scenarios, subjects performance is


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almost 100% correct. In the top scenario, they perform poorly.

It appears, then, that cuing after the first scene but before the second scene

prevents change blindness. This indicates that cuing draws the subjects attention

to one part of the entire scene, even though the scene is no longer present. Thus,

when the cue occurs in the bottom scenario, there must still be a representation of

the entire scene at the time of the cue. Cuing then allows a comparison to be madebetween the part of the scene cued and the corresponding part of the second scene.

In the top scenario, there is no cuing until the end. By that time, the initial whole

scene representation has been over-ridden by the second whole scene visual repre-

sentation, so no comparison is possible. This is why in the top scenario, unlike the

other two, there is change blindness.

The Landman/Lamme experiment, then, strongly suggests that there is a rich

representation of the whole scene/stimulus. Within this representation, there is a

representation of the rectangle that changes its orientation and of the orientation of

that rectangle. With cuing in the grey interval, part of this representation remains

available for comparison with the second scene representation in the bottom scena-rio; hence the improved performance.

What is represented need not be consciously represented, however. Specifi-

cally, it need not be the case that in the Landman/Lamme experiment, each block

orientation is represented at a conscious level. Furthermore, the fact that the whole

scene representation in the Landman/Lamme experiment is rich does not prove

that there is comparable richness in the visual representations of scenes with more

items. Still, the view I am proposing with respect to the crowds of balls can allow for

such richness. That is, it can allow that that the visual system encodes information

about each ball and its color just as it does with respect to each rectangle and its

orientation. In that event, my claim is that, depending upon how the eyes move, it

may well not be the case that there is a consciousrepresentation of each ball.

Where does this leave us with respect to change blindness? My answer is that

for at least some change blindness scenarios, we should accept the REPRESENTA-

TIONAL FAILURE hypothesis at a conscious level as opposed to the COMPARISON

FAILURE hypothesis at that level. The first hypothesis is self-explanatory; the

second is the view that change blindness results not from a failure to see anything in

the field of view but rather from a failure to compare properly conscious represen-

tations of the scene before and after the change.

In somecases of change blindness, it seems clear that the comparison failure

hypothesis is correct. Consider, for example, Dan Simons basketball experiment

(2002). In this experiment, a confederate asked an unsuspecting pedestrian on a

college campus for directions. The confederate was (or was not) holding a red and

white basketball. As the pedestrian was giving directions, a group of people walked

behind her and between her and the confederate, and one member of the group re-

moved (or added) the basketball. Fewer than 25% of the participants spontaneous-

ly noticed the change. However, when they were cued, an additional 50% reported


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the basketball change, and they were even able to state the unusual color of the bas-

ketball.

It seems plausible to suppose that the subjects who recalled the basketball

after the hint were originally conscious of it and its color (in the case that the bas-

ketball was present initially). They simply failed to spontaneously compare proper-

ly their initial conscious representation of the basketball with their later one.

Another point I want to stress is that in some cases of change blindness --

notably ones involving real life scenes -- it maybe that not only are some things in

plain view missing at the conscious level but also that others are added. When

shown a scene very quickly, subjects certainly sometimes report the presence of

things that are missing but that are compatible with the character of the scene. For

example, if shown very quickly a picture of a street scene and asked whether the

scene contained a fridge, subjects will deny it but if asked whether there was a fire

hydrant, they often will say yeseven though there was no fire hydrant. It seems tome not at all obvious (and very likely false) that the subjects actually experienced a

fire hydrant in the scene, but there is nothing in my overall view that precludes thispossibility (see here section VII).

I want now to go back to my earlier claim that in the crowd of balls example

Bill (ball #43) may well not be seen, given the actual eye movements. In making this

claim, I am not endorsing the view of ORegan (2000/2001) and others (ORegan

and Noe 2001) that things to which we are not attending are only potentially seen. I

am not supposing that there is a refrigerator light illusion, as it has come to be

called. This is the claim that just as a very unsophisticated person might mistakenly

suppose that the refrigerator light is always on, given that it is on whenever the

fridge door is opened, so we too in supposing in everyday life that there are things

we see to which we are not attending are making a comparable mistake. The fridge

door is only potentially on at all times and we only potentially see things to which

we are not attending. An adequate discussion of this claim requires that we turn our

attention to the topic of attention.

4. Attention: some preliminary remarks

Perhaps the most famous quotation on attention comes from William James.

He wrote:

Everyone knows what attention is. It is the taking possession by the mind in

clear and vivid form, of one out of what seem several simultaneously possible

objects or trains of thought.Focalization, concentration, of consciousness areof its essence. It implies withdrawal from some things in order to deal effec-

tively with others, and is a condition which has a real opposite in the con-

fused, dazed, scatterbrained state. (1890)

James here tells us that attending to an object is a matter of taking possessionof itmentally in clear and vivid form. The natural, intuitive way to express this thought

is as follows: one attends to something just in case one focuses upon it.


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Supposing that attention is a matter of focus, it seems clear that the relevant

focusing is not sense-specific. We can attend to a noise, a flash, a smell, a shape, for

example. We can also attend to spatial regions, but typically we attend to particu-

lars located in space and features of such particulars (e.g. color and shape). Contra

James, there is also evidence that we can attend to more than one thing at a time.

For example, if subjects are presented with an array of eight stationary dots, andthey are told to pay attention to the four dots that flash initially, they can continue to

track those four dots even if all the dots in the array begin moving around in irregu-

lar ways.5

Attention can be triggered by external stimuli that pop out (e.g., a red square

in a field of green squares) or begin suddenly (e.g., a flash of light or a loud noise).

This is bottom-up attention. Here (in the visual case) eye fixation and attention au-

tomatically go together. Attention can also be triggered by a decision or choice. In

these cases, focus can diverge from fixation. This is top-down attention. Top-down

attention is driven in part by the concepts exercised in the decision to attend.

Here is an example of focus without fixation:

If you fixate and focus on the plus sign in the middle of figure 7, you will be able to

discern which rectangles are lighter in color but not which ones have longer vertical

as opposed to horizontal sides. To discover that, you need to switch your focus to

5Not everyone agrees that in tracking the dots one attends to them. See Pylyshyn

2003.


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each rectangle in turn, and this you can do while continuing to fixate on the central

plus sign (Cavanagh et al 1999).

In general, when one attends to a thing, features of the thing are usually re-

vealed of which one was not conscious beforehand. Attention facilitates pattern or

object recognition not just by revealing new features, I might add. It also aids in the

cognitive integration of features into features of single objects and in the combina-tion of parts into wholes (Treisman 1980).

I want next to develop further the proposal that attention is a matter of men-

tal focus. As I have already noted, this proposal fits well with our ordinary ways of

thinking about attention. If I tell you to pay attention to what I am saying, I am ask-

ing you to focus upon my remarks. If I switch my attention from the oboe to the

strings, as the orchestra plays, I am switching the focus of my hearing from one to

the other. Or so we ordinarily suppose.

Ryle (1949), nonetheless, opposed the focusing view of attention. He claimed

that when one attends to something one is doing, there are not two activities here

but one done attentively. This is not, in general, true, however. A novice driver mayattend to her driving (as she would that of her instructor) by focusing on the gear

shifts, the position of her feet, etc without thereby driving attentively. Still, we

should agree with Ryle that there is such a thing as attending as an agent. Here one

performs an action A attentively and this is not an amalgam of two separate activi-

ties: performing A and attending to A. But there is also such a thing as attending as a

spectator(to ones own action or someone elses or something that is not an action).

This, I maintain, is a matter of ones focusing on that to which one attends.

Furthermore, attending as an agent requires attending as a spectator (though

not to the action one performs). One cannot fish attentively, for example, if one pays

no attention, while one fishes, to things relevant to catching fish and instead attendsto the joyful cries of the children playing nearby or a new game on ones iPhone.

Following Ryle, Alan R. White, a philosopher noted for his ordinary language

distinctions, held that the concept attendingis a polymorphous activity concept

(White 1964). What White meant was there are many different activities, the doing

of which can in certain circumstances count as attending and yet none of which in

other circumstances necessarily counts as attending. Another example of a poly-

morphous activity concept is the concept working. One can work by running or talk-

ing or sitting, but equally one can do each of these things without working. To say

that someone is attending, according to White, gives us no more idea as to what spe-

cific activities she is engaged in than to say she is working.

To describe someone as attending, on this view, is to say that there is some

specific activity the person is engaged in that is focused on something that occupies

her (where that same activity in another context when not focused on the relevant

thing does not constitute attending to it). For example, one can attend to an argu-

ment by reading it but one can read an argument without attending to it. This is

compatible with holding that attending is a matter of focusing; for we may say that


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what it is to focus on something is to engage in somespecific activity that is focused

on the relevant thing.6

These remarks about attention are intended to be consonant with how we

ordinarily think of attention. But prima facie they do not fit very well with some

scientific discussions of attention. In particular, they seem not to capture what

scientists sometimes call diffuse or ambient attention(Pashler 1998). Just howattention so conceived is to be understood is a topic to which I shall return later.

For the moment, I shall stick with attention understood in the typical ordinary, eve-

ryday way.

5. Attention and Seeing

Can you attend to a thing via the use of the eyes without seeing it? Given his

comments in the passage quoted earlier, it is clear that William James thought not.

For James, consciousness is part of the essence of attention. However, according to

Kentridge, Heywood and Weiskrantz (1999), blindsight subjects can attend to thingsin the blind hemifield without being visually conscious of those things. They cite as

evidence the fact that their blindsight subject was more likely to guess correctly

whether a circle had been presented in a given location Lin the blindfield if the loca-

tion was cued beforehand by bars just above and below L(bars that were them-

selves entirely within the blind field). A plausible view is that the bars attracted the

blindsight subjects attention to the spatial region occupied immediately afterwards

by the circle and thereby to the circle. On this view, he did not see the circle but he

did attend to it. So, it is possible to attend to something in the visual case and yet

not see it.

One might respond that the bars really onlydrew the subjects attention to a

specific region of space within the blind field. But even if this is true, there is loca-tional attention without locational consciousness and so attention does not require

consciousness, as James supposed. Moreover, in general when we attend to an oc-

cupied region of space, we cannot help but attend to the thing in that region of

space. Why suppose that this case is any different?

Further evidence that attention can occur without seeing is provided by

Jiang, Costello, Fang, Huang, and He (2006). They found that invisible pictures of

nudes (made invisible by a technique known as inter-ocular suppression) located on

one side of the visual field draw heterosexual subjects attention (as judged by their

performance on a later task for which the locus of attention is crucial) if the nudes

are of the opposite gender.7

6Creature focus, thus, is to be understood in terms of activity focus.

7Jesse Prinz (forthcoming) suggests that even though the subjects eyes saccade tothe nudes, the subjects do not attend to them. But if attention is not going to the

nudes at all, why do the subjects exhibit superior performance with respect to the

detection of the orientation of a Gabor patch flashed into the region of the nudes af-


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What about the other way around? Can one see a thing without attending to

it? A famous experiment by Mack and Rock (1999) seems to provide evidence for

the view that one cannotsee a thing without attending to it (and thus that there is a

refrigerator illusion). In this experiment, test subjects were given the demanding

task of determining whether the vertical arm or the horizontal arm of a cross is

longer. The cross was presented for a fifth of a second followed by a mask for half asecond. The purpose of the mask was to prevent any further processing of the visu-

al display after the cross disappeared from the screen.

terwards (as opposed to the orientation of such a patch flashed elsewhere)? It is

true that the high contrast stimulus acts as an attention lure, but this does not prec-

lude attention from going to the nudes. In general, when ones eyes go to a stimulus

S, even if one is focusing elsewhere, ones focus is drawn to S, if only for a few mo-ments. Furthermore, the discovered attentional effect is very specific: when the

nudes are of the same gender as the subjects, attention is repelled (as shown by in-

ferior performance with respect to Gabor patch orientation). The obvious conclu-

sion is that emotion-laden stimuli modulate selective attention and do so even

when the stimuli are invisible. Prinz adds that if attention were going to the nudes,

we might expect to see increased activation in the ventral stream, where object re-presentations are processed and, according to Prinz, fMRI studies of inter-ocular

suppression do not show increased ventral processing. Let us grant that the evi-

dence shows that in general there is no increased ventral processing with respect to

suppressed stimuli and that this indicates that attention does not go to the sup-

pressed stimulus. What is supposed to follow? In general, the eyes do not saccade

to the low contrast stimulus. In this case, they do; and for this case, fMRI studies

have not been done.


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In the first three trials, the subjects were presented with the cross alone before the

mask. On the fourth trial a small black square was located very close to the cross.

Subjects were not expecting anything different about this trial and so they were not

looking for something new. Immediately after the trial they were asked whether

they saw anything on the screen before the mask appeared that had not been there

in the previous trials.Roughly of the subjects did not report seeing the small, dark square even

though it was very close to their fixation point. All the members of a control group

who were not given the demanding attentional task reported seeing it. The condi-

tion of the test subjects was dubbed inattentional blindness by Mack and Rock.They took it to show that attention is necessary for visual perception.

Now it certainly seems right to say that the test subjects who failed to report

seeing the black square did not attend to it. But it is also the case that they were not

ableto attend to it, given that their attentional resources were exhausted elsewhere.

One possibility then is the Mack/Rock view: attention to a thing is necessary for

visual perception of that thing. On this view, there really is a refrigerator light illu-sion.

Another possibility not considered by Mack and Rock is that in some special

circumstances attention to a thing is necessary for visual perception of it. After all,

in their experiment, the visual stimulus is brief, unexpected, presented while the

subjects are attending elsewhere, and followed by a mask (Mole 2004). This possi-

ble explanation, however, does not accommodate easily the results of other experi-

ments involving inattentional blindness in which the circumstances are not so ob-

viously special.

A third possibility is that the abilityto attend to a thing is necessary for visual

perception of that thing. On this view, one fails to see a thing if one cannot attend toit. Still one can see a thing if one does not attend to it. This view is the one I favor.8

One reason is that it accommodates nicely the results of Sperlings famous experi-

ment (1960) in which subjects are presented very briefly with an array of 12 letters

(see below).

8There is a fourth possible explanation worth mentioning, namely that subjects do

indeed see the stimulus but, given its brevity, they immediately forget it and thus fail

to report it (Chalmers 2008). This seems completely implausible, however. Thebrevity of the stimulus cannot be the crucial factor since other experiments on inat-

tentional blindness involve stimuli that are present for several seconds. Perhaps it

will be replied that the subjects fail to attend to the stimulus in the Mack and Rock

experiment, and that is why they forget it. But failing to attend to the bars on the

left of the central spot in figure 3 does not prevent consciousness of the bars and

memory of them afterwards. So why should it make a difference here?


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Sperling found that subjects were only able to identify 3 or 4 of the letters if told

simply to identify as many as possible. However, if a tone was sounded immediately

after the array disappeared (high, medium or low indicating which row the letters in

which the subjects were to identify), the subjects managed to get all 4 right (typical-

ly). The obvious explanation is that the tone directed the subjects attention to aparticular row. Since the subjects did not know in advance which row would be the

relevant one and the subjects reported that they saw each letter even though they

could only identify the letters in the row corresponding to the tone, it seems very

plausible to hypothesize that there were letters the subjects saw to which they did

not attend.

Even though the subjects can only identify 3 or 4 of the letters in Sperlings

experiment, they can say accurately how many letters were present on the basis of

their experience. This is one difference between the letters in Sperlings array andthe bars on the right of the central spot (see figure 3). Each letter is seen but each

bar on the right of the spot is not. It is worth emphasizing that the claim that each

letter is seen does not entail that each letter identity is represented at a conscious

level. (One can see the letter A, for example without seeing it as an A or indeedwithout being able to identify the various letter segments.) It could be that as atten-

tion is directed to the row corresponding to the tone, aspects of the letters in that

row that were only represented unconsciously prior to the tone become part of the

phenomenology.9

9Indeed, this is the most plausible view; for if a numeral or pseudo-letter is substi-

tuted for one of the letters in a Sperling array and subjects are attending to a row

containing only letters, they still take the array to be filled with letters. In this case,

the subjects see the numeral or pseudo-letter, but they are not conscious of the fact

that it is a numeral or pseudo-letter. For more on the effects of attention on phe-

nomenology, see the next section.


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Perhaps it will be objected that in some cases we see things too quickly for us

to able to attend to them. It has been found, for example, that when subjects atten-tion is taken up with a very demanding task in the center of the field of view, they

can nonetheless discriminate between famous and non-famous faces flashed into

the periphery even for times as short as 60 msecs (Li et al, 2002).

This is too hasty. It is certainly true that the time of presentation of the peri-pheral stimulus is too short for voluntary top-down attention to lock onto the stimu-

lus. Furthermore, if indeed all top-down attentional resources are devoted to the

task in the middle, evidently there is no top-down attention left to allocate to the pe-

riphery. Still, bottom-up attention remains available and there is evidence that bot-

tom-up attention can be switched involuntarily to a sudden onset stimulus lasting

only 60 msecs (Connor et al, 2004).

In another experiment, Li, Iyet, Perona and Koch (2004) presented images of

scenes for as short a time period as 27 msecs. After each trial, subjects wrote down

everything they could freely recall. There were no forced alternative choices. It was

found that subjects could accurately recall the gist of each scene. Here, apparently,they saw things in the scene even though they were unable to attend to them.

Again, however, there is no clear empirical reason to deny that bottom-up at-

tention picks up on each thing on which the subjects report. After all, if subjects can

covertly switch attention involuntarily to a single 60 msec stimulus located away

from the fixation point, it does not seem far-fetched to suppose that where there are

several stimuli suddenly presented in the foveal region, they can catch the subjectsattention simultaneously in a single shorter glance. Furthermore, it is hard to see

how attention could fail to be operative here with respect to each reported item; for

correctly reporting on an items identityrequires having noticed the item and, in sodoing, having correctly taken it to be a so-and-so. Intuitively, that necessitates that

the item catch ones attention.

In the next section, I want to flesh out further my preferred view of attention

and to connect it with some scientific claims about attention.

6. More on the nature of attention

One issue I have not taken up yet is whether attention is an activity with an

intentional content. Let me begin with some general remarks about intentional

states and activities.

From(1) Macbeth hallucinated a dagger,

we may infer

(2) Macbeth hallucinated something.

But (1) does not entail

(3) There is (exists) some dagger Macbeth hallucinated.


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If there really were some daggerMacbeth was hallucinating, he would not be hallu-

cinating at all! Indeed, if there really were any thingMacbeth was hallucinating,

then he would not be hallucinating. So, the quantifier something or some object

cannot safely be exported in contexts such as (2).

Here is a further example. Ponce de Leon was searching for the fountain of

youth. So he was certainly searching for something. But it is not the case that thereis (or was) a fountain for which he was searching.

One view is that these points apply to the case of attention. Consider, for ex-

ample, the Kanisza triangle.

Here one can attend to the triangle. But there is no such triangle.10 Still, one

is attending to something. Even though one is attending to something (a triangle),

there is no triangle to which one is attending. These features of attention mark it

out as an activity with an intentional content. Or do they?

10This might be contested (Shelley Kagan did so in conversation). But ones expe-

rience of a triangle here integrally involves the experience of a contrast in bright-ness within the region of the triangle and outside it and, in reality, there is no such

change in contrast. One attends to a bright white triangle,but there is no bright

white triangle. (The particular example is of no great importance anyway, since one

can surely hallucinate something and attend to one part of what one hallucinates

rather than another. Furthermore even if one knows one is hallucinating a complex

scene, one can switch ones attention (focus) from one part of the scene to another,

even though there are, in reality, no scene parts to which one is attending.)


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One potential problem for the intentionalist view of attention is that the con-

text P attends to x is extensional at least to the extent that co-referential terms thathave referents are substitutable salva veritate in the x position. Thus

(4) Paul attends to the cat,

(5) The cat = Dorothys petentail

(6) Paul attends to Dorothys pet.

Similarly,

(7) John attends to the color of the ball

(8) Red = the color of the ball

entail

(9) John attends to the color red.

So, P attends to x is not like P fears x or P desires to meet x,for example. A ladyof the evening in nineteenth century London might have feared Jack the Ripper

without fearing the polite man who gave her flowers each day even though, as it

turned out, Jack the Ripper was that man. I can desire to meet Ernst Mach without

desiring to meet the shabby pedagogue at the end of the bus who unknown to me is

Ernst Mach. By contrast, necessarily, if I attend to a and ais the same as b, then I at-

tend to b.

Why is there this difference? Well, the London woman, in fearing Jack the

Ripper without fearing the polite man who gave her flowers each day, was fearing a

certain individual conceived of in one way and not in another. By contrast, we may

suppose, attending to a thing does not require any particular way of conceiving ofthat thing.

There are various ways in which this general proposal could be developed

further. Consider the visual case. The view I prefer is that the content of visual at-

tention is either a Russellian singular proposition (if there is a thing that is the ob-

ject of attention) or a proposition that is just like such a proposition except that it

has a gap in it where an object should go (if there is no thing at all to which one is

attending). This makes the content robustly nonconceptual: only wordly entities

figure in the content. Of course, if attending to a thing has a propositional content

then there should be correctness or truth-conditions associated with it. But does

this really make sense? What are the correctness or truth-conditions forfocusingon

a particular thing, an apple, say?

In the visual case, I maintain, one attends to an item via ones visual expe-rience being focused on it (at least where a visual experience is present).11 This

proposal respects the general claim made earlier that attending to a thing is a mat-

11As noted earlier, it is not always true that experience is present along with atten-

tion. In some abnormal cases, the visual phenomenology is missing.


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ter of engaging in some specific activity that is focused on the thing; for in the nor-

mal visual case, the relevant activity is visually experiencing. Now the proposal that

visual attention is nonconceptual and propositional goes naturally with the view

(held by many) that visual experience is nonconceptual and propositional (Tye 2009

and 2010).12

The activity of focusing upon a given thing comes about here via ones expe-rience focusing on the thing. That involves the experience representing the thing at

a conscious level in more detail than it would were the experience focused else-

where, with the result that one is in a better position to discriminate the thing and

its features. With a change in focus, then, in the normal visual case, there is a cor-

responding change in the content of ones experience.

This is nicely illustrated in the following example. The patches in figure 11

are known as contrast patches.

12In the case of what might be called intellectual attention, I do not hold that the

activity of attending has a nonconceptual content. In this case, the relevant specific

activity is conceptual, namely thinking, and where there is a thing about which one

is thinking, attention to that thing requires no one way of conceptualizing it. Atten-

tion here requires that the activity of thinking not only be about the relevant content

but also be focused on it. The topic of intellectual attention deserves discussion in

its own right.


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Begin by both fixating and focusing on one of the dots. The patch to the right of the

dot looks to have greater light/dark contrasts. Now switch your focus to the patch

to the left while continuing to fixate on the dot. With the new focus, the patch to the

left looks to have roughly the same light/dark contrasts as the patch to the right (or

at least to be much closer in such contrasts to it). According to a study by Carrasco

et al (2004), shifting attention increases apparent contrast by 3-6%. This is a

change in the content of experience.

Are there any possible cases in which there is a change in attention without a

change in the content of visual experience, assuming that visual experience is

present? I am not aware of any. All the cases adduced in the literature (Chalmers

2004, Nickel 2004, Speaks 2010, Wu forthcoming) seem to me to involve a subtle

change in the content of the experience (Tye forthcoming). Still if there are any such

cases, what remains to underwrite the claim that the experience is focused on one

item rather than another is the role the experience plays in improving speed and

accuracy of discrimination with respect topossiblechanges in the item. Where an

experience is focused on object O, the subject of the experience is in a better position

to discriminate possible changes in Othan would be the case if the experience were

focused elsewhere. Normally, this is a direct reflection of the richer content of the

experience with respect to the object upon which it is focused, and a correlative

richer visual phenomenology, but perhaps conceivably there are cases in which theexperience has non-conscious properties that are partly responsible for the superior

discriminatory response.

I want now to return to the topic of diffuse attention. The term attention, as

it is sometimes used in psychology, is broader in its application than in ordinary

contexts. It encompasses both what is sometimes called focal attention and what

is called diffuse attention, where focal attention is just attention, as I have been

concerned with it centrally in this essay. The relationship of diffuse attention to at-

tention, as understood thus far, is like that of background lighting to a spotlight.

Thus, if we normally visually attend to an item by undergoing anexperience that is

focusedon that item, then it is natural to think of diffuse attention to an item as oc-

curring via experience of the item that is notfocused on it. Given this usage, in thecase of Sperlings experiment, one does diffuselyattend to each letter, given that onesees each letter.

Still, why does diffuse attention count as attention? The answer, I suggest, is

that in diffuse attention, there is a selection process at work that selects particular

things and properties and makes them available for further processing, thereby im-

proving the speed and accuracy of appropriate discriminatory responses with re-


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spect to those items. In this way, diffuse attention is like focal attention. The differ-

ence is most notably in the selection class. In focal attention, where visual expe-

rience is present, the items upon which the activity of focal attention operates are

items that are experienced. In diffuse attention, in such cases, the relevant class

consists of pre-conscious visual stimuli. Visual consciousness selects from among

these stimuli with the result that not everything visually represented is visually ex-perienced. There is, then, ausage of the term attention under which we really do

not see things unless we attend to them. Under this usage of attention, there is arefrigerator light illusion after all, though this is a misleading way of putting things,

since in everyday life attention is not used so broadly. Thus, the ordinary man, in

supposing that there are things he sees to which he does not attend, is under no

such illusion.

From this perspective, the debate between those who hold that attention is

diffuse and graded and such that there is no consciousness outside or beyond it and

those who hold that attention is focused and discrete and such that there is con-

sciousness without it is verbal. Different parameters are in play for the relevant se-

lection process.

VII. The vehicles of conscious awareness

Philosophers and psychologists who take change blindness to be a purely

cognitive phenomenon as opposed to a failure to see any thing in the field of view

often implicitly endorse a clear, color photograph model for the vehicles of con-

scious awareness.13 On this view, in the case of the two crowds of balls, there is a

mental snapshot of each crowd. Each snapshot pictures each ball in the relevant

crowd. There is change blindness because an inaccurate comparison is made be-

tween the two snapshots.A better model is provided by drawn pictures. Think about the case of an art-

ist drawing a picture of a scene. The artist begins by fixating on some part of the

scene. Some things in the scene are left out of her picture altogether. Others are

very richly depicted. We might be a bit like such an artist as we see the things

around us.

It is worth noting that the drawn picture model of visual experiences allows

for thepossibilitythat some things not in the scene are experienced. Artists some-

times embellish the scenes they draw, adding items that are not present. Upon oc-

casion, we might do that too as we see the world around us (see here section 3).

The idea that seeing things is like drawing pictures is reminiscent of StephenKosslyns view (1980, 1994) of mental image generation.14 Kosslyn argues that im-age generation is not like retrieving a clear photograph from memory. Rather it is

best taken to be a constructive process similar in certain ways to drawing a picture.

Likewise, I am suggesting for visual experiences. This, I hasten to add, should not be

13See, e.g., Dretske 2010.14See also Block 1983, Tye 1991.


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taken to suggest that, in my view, seeing is inherently conceptual. It is not. Con-

cepts may play a causal role in influencing how we direct our attention and relatedly

how we experience things as being, but concepts are not exercised in (thing) seeing

itself. Just as an artist may draw a picture involving all sorts of irregular shapes and

determinate shades of color for which the artist has no general concepts, so we too

in seeing the world around us may lack the concepts needed to state the accuracyconditions for the visual experiences embedded in such seeing.

VIII. Do we see all the things in the visual field large enough for us to see?

If all is used distributively, the right answer is no there are typically (of-

ten) things large enough to see that we fail to see. If all is used collectively, the

right answer is yes we do see all the (non-occluded) things in the field of viewlarge enough to see.

So, there is a sense in which both sides in the debate about what we see are

right. However, the heart of the debate is about whether we see each thing in plainview and here I have been arguing those who advocate the representational failure

hypothesis for many of the cases of change blindness are on the winning side.15

Michael Tye

The University of Texas at Austin

15Earlier versions of this essay (or parts of it) formed the basis for one of my Nelson

lectures at the University of Michigan in 2007, a symposium talk at the Tucson Con-sciousness Conference in 2008, a symposium talk at the Association for the Scientif-

ic Study of Consciousness in Berlin 2009, another symposium talk at the Pacific APA

in 2010, a talk at the European Graduate School in Lausanne 2009, and colloquium

talks at the University of Illinois at Urbana/Champaign in 2007, at Neu-Phi in Bos-

ton, 2009 and at Yale in 2009. The essay was also discussed at a meeting of the NYU

Mind and Language seminar in Spring 2010 and I am indebted to Jesse Prinz and es-

pecially to Ned Block for their comments.


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Documents

Attention Seeing and Change Blindness