5
The What and Why of Priority
Structures
Interpretation and Functional Role
1
Interpretation and functional role
The last chapter has argued that attention is constituted by priority structures. We
have seen how the priority structure view can be developed. We can identify priority
structures in terms of the elements of the structure (psychological parts) and a
structuring relation (weak priority). By taking these components of priority structures,
we were able to define priority systems with various positions, such as top priority.
Further, we were able to provide a unified account of the various forms of attention.
But some important questions were postponed. Roughly, they fall into two categories.
On the one hand, there are questions regarding the details of how to interpret priority
structures.
What exactly are priority structures? Questions like this will occupy the first half of
this chapter. We will have a closer look at the structuring relation, the elements and
the size of priority systems. I suggest that the weak priority relation most likely has
no reductive identification. I argue further that it is an external relation, i.e. whether it
holds is not fully determined by the intrinsic properties of the psychological parts it
relates. Psychological parts (the elements), I argue, are best understood as aspects of a
subject’s mental life that are ‘carved out’ by attention and not as mental atoms that
attention merely puts into priority relations. Finally, I argue – based on empirical
evidence – that most subjects most of the time have a single priority system that
connects all parts of the current slice of their mental lives. There is thus, for example,
no separate visual attention system.
On the other hand, there are questions about the role of priority structures.
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The What and Why of Priority Structures
Why do we have priority structures? Questions like that will be the topic of the
second half of the chapter. I will contrast two conceptions of the central function of
attention, an information pruning conception (according to which attention protects us
from information overflow), and an organizational conception (according to which
attention organizes the mind to allow for flexible action). I will argue for the
organizational conception. I will then look closer into the functional role of
prioritization. Prioritizing, I argue, plays an important role for behavioral decoupling,
i.e. the capacity to decouple behavior from a specific environment. I close the chapter
by comparing the priority structure view of attention with the view that attention is
selection for action. Both share a similar conception of the functional role of
attention. I argue that the priority structure view is the better way of developing this
conception.
2
2.1
How to interpret priority structures
Priorities I: reductionism or primitivism?
Some readers may impatiently wait for an answer to the question: but what is relative
priority? What is it for some psychological part to have at least as much priority as
another one?
Readers of this persuasion may be waiting for a reductive account of weak priority
(either a reductive identification with a low level phenomenon or a reductive account
in terms of other subject level phenomena).
I don’t believe that there is such a reductive account. My own view is a form of
primitivism (though not radical primitivism).1 According to the primitivist position
there is no way of non-circularly specifying what weak priority is. When we try to say
what it is for some aspect of a subject’s mental life to have at least as much priority as
another, we will quickly run into explanatory circles. We might, for example, say
something like: if a mental state is prioritized then it occupies a lot of the subject’s
attention. But, of course, what it is to occupy a subject’s attention was in turn
explicated by appeal to what is prioritized over what.
While there is no reductive identification, I hope that the last chapter has
demonstrated that we could still provide an informative account of the various forms
of attention and their interrelations. Furthermore, the second half of this chapter will
develop a view on the central functional role of prioritizing. I do not believe that a
reductive account of priority can be given in terms of this role, though (we would
again run into circles).
1
The view, as I mentioned before, has the same shape as the view about knowledge defended in recent work by Timothy
Williamson (2000).
How to interpret priority structures
93
What primitivism rejects is a reductive identification of weak priority. It denies that
an account of what it is for a subject’s mental state to be of higher priority than
another can be given, for example, in terms of biological or computational facts.
Primitivism does not reject a reductive explanation of priority (see Chapter 1, p. 14 ff
for this distinction). It is highly plausible, for example, that facts about a subject’s
priorities supervene on and are metaphysically explained by biological and
computational facts about her brain.
Indeed, for some cases we know a lot about the facts that realize which mental states
are prioritized over which others. Consider, for example, a subject who – to switch
our examples a bit – is visually attending to a tiger. Maybe she is in the woods, and
the tiger caught her attention. Her seeing of the tiger, let us assume, is prioritized over
all other parts of her visual experience. In a case like this, prioritization is – drawing
on what we know about attention – correlated with all of the following: faster reaction
times to when the tiger moves;2 lower detection thresholds;3 the visual representation
of the tiger will have higher acuity than other visual representations;4 visual contrast
will increase for the tiger, the tiger’s color might look a bit more saturated, the tiger
might look a little bigger, and the tiger’s movements might appear to last a little
longer;5 the tiger might look a bit closer;6 the blurry line between the tiger and its
background will be more likely attributed to the tiger than to the trees behind it; 7 the
subject will be more likely to reason about the tiger (given that we are dealing with a
human subject and not a zebra); the subject will be more likely to prepare actions
with respect to that tiger (unless she just looks at the tiger from the safety of her cabin
with no point or purpose at all);8 if our subject forms beliefs about whether there is a
tiger those beliefs will tend to be more reliable than they would otherwise have been
(though some automated actions will lead to more reliability without attention);9 and
the subject will often take information about the tiger to be more relevant than
information about other things (though not if her mind has been wandering and she
just happened to glance at the tiger).10 These, and probably others, are the facts that
are correlated with having a priority structure with a seeing of the tiger in top
position. Some of these facts are at least part of the metaphysical explanation of
having that priority structure.
2
Styles 2006, or any other textbook on attention.
ibid.
4
ibid.
5
Carrasco, Ling and Read 2004.; Gobell and Carrasco 2005; Tsal and Shalev 1997; Gobell and Carrasco 2005; Anton-Erxleben,
Heinrich and Treue 2007; Fuller and Carrasco 2006; Liverence and Scholl 2011; Tse et al. 1997.
6
The effect of attention of perceived spatial distance is well studied by studying its effects on the percpetion of ambiguous
figures. See Rubin 1915/2001 and Driver and Baylis 1996 for the Rubin Vase; Kawabata 1986 and Matsuura and Ichikawa 2003
for the Necker Cube. What these studies show is that the attended aspects of a scene tend to be perceived as foreground, and
closer to the viewpoint of the perceiver.
7
Driver and Baylis 1996; Vecera 2000; Vecera, Flevaris and Filapek 2004; Wagatsuma, Shimizu and Sakai 2008, Kimchi 2009.
8
See Wu 2014. For more discussion see Sec. 3.3 below.
9
See Wu 2014.
10
For the connection between relevance and attention see Sperber and Wilson 1995.
3
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The What and Why of Priority Structures
What primitivism denies is that either the facts described in the last paragraph or any
sub(or super)set of them are what it is to prioritize seeing the tiger over other mental
states.
According to primitivism the explanation of different instances of the weak priority
relation will differ from each other. Consider prioritizing seeing a color (as in feature
directed attention): many of the correlates above will not be present in a case of such
feature directed attention. The explanation of the subject’s priority structure in this
case differs from the one for object directed attention. Consider also prioritizing a
sound our subject hears, or a surface she feels; or prioritizing an object by thinking
about it; or by being afraid of it, or by being happy about its presence. Each of these
instances of prioritization does have an explanation, but the explanation is different
from case to case.
For comparison, consider again the case of primitivism about knowledge: suppose
that our subject knows that Paris is the capital of France. There will be a story about
how it is that she knows this. She has read it in a book, which is a reliable source. Or
she has checked on a map; or maybe he has seen a certain street sign. The fact that
our subject has that knowledge also will have a variety of effects. Effects on whether
she is likely to find Paris; effects on what she is likely to say; whether her belief that
Paris is the capital of France will be easy to shake; and much more. But none of this
(and nothing else), according to the primitivist about knowledge, will amount to an
account of what it is for someone to know something. Some features will be present
in this case, but not in a different case (e.g. a case where Sue knows that there is a red
object in front of her, or where Anna knows that a = a). While in each case there will
be some explanation for how someone knows something and what that knowledge
does for her, giving such a story will not amount to an account of what it is to know
something.
The argument for primitivism and against a reductive account of priority – insofar as
that is an argument – is just this: insofar as anyone has ever tried to provide a
reductive account of attention it has failed (and as we have seen in Chapter 1 most
psychologists have long given up that very idea). So, by induction any future
reductive account is likely to fail as well.
Before we move on, let me note that whether primitivism or reductivism is true will
not really matter for the rest of this book. Suppose that, at the end of the day, we are
able to provide a reductive identification of weak priority. If there is such a reductive
identification, we can just replace where I speak of ‘x1 has at least as much priority
than x2’ with that reductive account. Indeed, a proponent of reductivism may be
happy about what this book provides, since now she knows exactly what we need a
reductive account of.
For now, I will proceed without a reductive identification of weak priority.
How to interpret priority structures
2.2
95
Priorities II: comparative or absolute?
Independently of whether there is a reductive identification of weak priority, one
might wonder about what kind of relation it is.
I have introduced weak priority as a relation between two mental states. One mental
state is of at least as much priority as another. Priority thus ranks occurrent mental
states, just like preference ranks options.
But, one might ask, is the relational conception of priority really the most
fundamental one? One might suggest that relative priorities reduce to absolute
priorities. To see the shape of this idea consider preferences and utilities. Someone
might propose that whether a subject prefers option A over option B is explained by
the fact that the utility she assigns to A is greater than the utility she assigns to B.
Similarly, someone might propose that whether a subject prioritizes A over B is
explained by the fact that the priority she assigns to A is greater than the priority she
assigns to B. Absolutism about priority thus would be the view that says that absolute
priorities are more fundamental than relative priorities. Relationalism about priority,
by contrast, says that relative priorities are more fundamental. An absolutist about
priority will think that what it is for x1 ≥ x2 to hold just is for x1 to have priority P1 and
for x2 to have priority P2 and for P1 to be greater or equal to P2 (where P1 and P2 are
intrinsic properties of the respective mental states).11 According to absolutism priority
relations get reduced to absolute priorities. Relationalism, by contrast, denies this
view. According to relationalism the most fundamental notion of priority is a
comparative notion.
The last paragraph put the issue in terms of whether comparative or absolute
priorities are more fundamental. But absolutism need not make a commitment about
the nature of relevant intrinsic properties. They could be any intrinsic properties. We
can formulate a more general version of the distinction between absolutism and
relationalism as follows. Consider that weak priority is a dyadic relation between
mental states. According to absolutism this relation is an internal relation in the
following sense.
Internal Relation
A dyadic relation x1Rx2 is internal =Def what it is for x1Rx2 to
hold is fully explained by the intrinsic properties of x1 and x2.
Relationalism about priority, which considers the comparative notion as the
fundamental one, by contrast, must deny the internal relation view of priority.
According to the relational view, priority is an external relation:
11
A property of x is intrinsic just if it is a property that any duplicate of x would share. For more detail see Langton and Lewis
(1998). While there are debates about this definition (or similar ones), I hope that they won’t matter for my present purposes.
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The What and Why of Priority Structures
External Relation
A dyadic relation x1Rx2 is external =Def what it is for x1Rx2 to
hold is not fully explained by the intrinsic properties of x1 and x2.12
The paradigm of an internal relation might be the relation of having more mass than.
Whether two things bear that relation to each other is completely fixed by how each is
intrinsically (i.e. by the mass of each).13 The paradigm of external relations are
distance relations. How far one object is from another is evidently not fixed by the
intrinsic properties of each object. Internal relations thus are relations that “drop out”
of a more fundamental description, while external relations do not drop out. If
absolutism were right, then weak priority would be an internal relation: whether one
psychological part is weakly prioritized relative to another would be fixed by the
intrinsic properties of each psychological part. According to relationalism, by
contrast, weak priority is an external relation. We can thus formulate the respective
views as follows.
Priority Absolutism
Weak priority is an internal relation.
Priority Relationalism
Weak priority is an external relation.14
Which view is correct: priority absolutism or priority relationalism?
Let us first consider empirical considerations.
The organizational role of attentional prioritization speaks in favor of the relationalist
conception. As we will see in the second half of this chapter, the central role of
prioritization is to facilitate flexible behavior. For the execution of this function any
alleged intrinsic priority property would be an idle wheel. For comparison consider
that you would like to organize some books in terms of their priority on your reading
list. The absolutist would solve this problem by first assigning a priority value to each
book (maybe a number in the interval [0,1]), and then use that value to order the
books accordingly, e.g. from the one with the lowest priority value to the one with the
highest value. Since the point of prioritizing is to arrive at the final ordering, this
procedure is inefficient. It uses a lot of information in the first step (is the value of
this book .4 or .5?) that then is discarded at the second step (since the exact priority
value will make no difference to the ordering). The same holds for attentional
prioritization: the computational problem that such prioritization solves (organizing
the mind) is solved most efficiently without absolute levels of priority. So, we have
no reason to think that we have evolved minds that operate with absolute priorities.
Priority relationalism is also most consistent with what we know about how our
brains actually solve that computational problem: if we look at the mechanisms that
implement attention we find that they implement relative priority and not absolute
priority. One of the most popular current approaches to the mechanisms of attention,
12
As Schaffer (2010b) points out there are other important senses of the notion of an internal relation. These will be significant
in our discussion of phenomenal holism in Chapter 9. For now we can neglect them.
13
The case of mass (like any other one) is not uncontroversial, see Dasgupta (2013).
14
This is a minimal commitment of relationalism. One might specify a more substantial characterization of the “comparative”
character of priority.
How to interpret priority structures
97
as we have seen in Chapter 1, is the biased competition approach. On this approach
neuronal representations inhibit each other in a process that gets biased through topdown signals from motivational and decision making areas of the brain (see
Desimone and Duncan, 1995). In this competition process we can define relative
priority, but we cannot define any notion of the absolute strength of a neuronal
representation. Absolute firing rates, and other monadic properties correspond to the
ordinary properties (such as shape or color) represented by that neuronal population,
while relative properties (such as relative firing rates or relative synchrony)
correspond to attentional priority. What determines success in the competition
process thus are relations (or comparative measures) between the properties of
neuronal populations and not the absolute amplitudes of neuronal firing, synchrony
and the like.
So, the more straightforward empirical considerations seem to support priority
relationalism.
But what about other, more philosophical, considerations?
Some people might think that those favor the absolutist conception. Start with
something mundane. Suppose that your attention is concentrated on the book you are
reading. But then you start to doze off. It is natural to say that your level of attention
diminishes. It is not that now you are focusing on something else than the book.
Rather, you are less focused overall. The natural explication of such a mundane
happening on the priority structure view seems to be that your overall level of priority
can vary: it was high first and then lower. But on the relationalist conception this is
impossible. Relationalism has to deny any difference between a state where the
subject has overall low priorities, and another state that preserves all the weak priority
relations and yet she has higher priorities. Relationalism has to deny that such
variations in overall priority are possible.
So, if such variations are possible, then absolutism must be correct.
Yet, to accept absolutism fro this reason would be too quick. It is important to note
that it is not only relationalism that has to deny the possibility of something that
seems intuitively possible. Absolutism also has to deny that certain situation that
seem possible are in fact possible. Absolutism has to deny that relative priorities can
be intransitive. Consider preference for comparison. Actual agents sometimes have
intransitive preferences. You might prefer apples to oranges, prefer oranges to
bananas, and also prefer bananas to apples. An intransitive preference ordering like
this is plausibly irrational. But that does not mean it is impossible to have such an
irrational preference ordering. An absolutist about preference cannot account for
intransitive preferences. Preference can be reduced to intrinsic utilities or even fix
intrinsic utitilities only if they are transitive.15 But now priorities, it seems, may also
be intransitive. Consider, for example, certain high level priorities, i.e. when my
attention is occupied by projects like caring for my children, or writing a book. It
15
See e.g. Hansson and Grüne-Yanoff 2012 for an overview.
98
The What and Why of Priority Structures
seems that some subjects may well have intransitive priorities of that sort, just like
they may intransitive preferences. I might prioritize my work over spending time with
my friends, spending time with my friends over exercising, and yet also prioritize
exercising over my work. Whether, for example, perceptual priorities, are ever
intransitive I take to be undecided. Whether or not priorities are transitive then seems
clearly a contingent matter and an empirical question. But absolutism about priority
rules out the intransitivity of priorities as a matter of metaphysical impossibility.
So, both relationalism and absolutism have to deny what may seem a possibility.
Which way should we go?
I believe that relationalism is more plausible because the cases that would make it
problematic have independently plausible re-descriptions that do not involve
variations in overall priority (considered as abstract intuitions about such variations
the intuitions seem to be unstable and likely depend on one’s background
philosophical view, and thus may not be stable grounds for theory building).
Consider that the difference between the highly focused state before dozing off, and
the less focused state after dozing off is very naturally described as a variation in
overall vigilance or arousal. These differences in arousal or vigilance can be captured
by relationalism (indeed we can distinguish a number of different dimensions):
First, low arousal states tend to be characterized by distributed and not spiky priority
structures. William James describes the “real opposite” of attention as situations were
the sounds of the world melt into confused unity, the attention is
dispersed so that the whole body is felt, and the foreground of
consciousness is filled, if by anything, by a sort of solemn sense of
surrender to the empty passing of time.16
Second, there is a dimension of vigilance that corresponds to a subject’s tendencies or
dispositions for changing or keeping certain priority structures. A highly vigilant
subject, has an overall tendency to adapt her priorities in accord with changes in her
environment, while a subject who less vigilant has such tendencies to a lesser degree.
To adapt an idea by Wayne Wu’s (2014, p. 95), a hyper-vigilant animal like “gazelle
drinking at a water hole … [is] constantly raising its head to scan the environment,
disrupting continuous drinking.”17 One dimension of vigilance thus can be cashed out
in terms of dispositions to have certain priority structures.
Third, and relatedly, levels of vigilance can be distinguished in terms of a subject’s
capacity to sustain attention for an extended period of time. A highly vigilant subject
16
James 1981 [1890], p. 404.
Wu uses this characterization to defend the selection for action theory of attention. The characterization, though, can be
adopted for the priority structure view as well. See Sec. 3.3 below for a discussion of the relationship between the selection for
action theory and the priority structure theory.
17
How to interpret priority structures
99
normally has her priorities stably dictated by the activity she is performing, while this
will not be the case for the low vigilance subject.18
Differences in the level of vigilance understood along the ways just mentioned, I
believe, are plausible accounts of the differences in overall attentiveness found, for
example, in the subject who was dozing off. They are compatible with relationalism.
But let us suppose that some alleged cases of variations in overall priority cannot be
plausibly described in terms of vigilance. In this case the relationalist can use the
following strategy. We say that a subject’s overall priorities are relatively high if
there are many mental states x2 such that if the subject had x2 together with all of her
actual mental states, then for all of those actual mental states x: it would be the case
that x ≥ x2.19 So, a relationalist can account for the scenarios an absolutist deems
possible in terms of certain counterfactuals. High or low levels of overall priority are
captured in terms of what would happen, were the subject to have other mental states
than her actual ones.
The overall balance of reasons then, in my view, speaks in favor the relational notion
of weak priority, and not the absolutist notion. We can let the existence of intransitive
priorities be an empirical matter, and we can provide a plausible account of what may
have seemed to be cases that support the absolutist conception.
2.3
Psychological parts: propositional vs. priority partitioning
Priority systems are built from what I have called psychological parts and the relation
of weak priority between them. In the last chapter I said that the psychological parts
are aspects of a subject’s current mental life, occurrent mental states, events or
processes. Further, we have seen a range of examples of the psychological parts of
priority systems. Can we say anything more?
In this section I argue that we should not think of psychological parts as the
independently given building blocks of priority systems (in this sense they are
different from books). The activity of attending creates a partioning of the subject’s
current mental life (or an aspect of her current mental life) together with priority
relations between the parts. It does not take some independently given aspects of that
mental life and then order those aspects in terms of their relative priority. Attention is
what brings about priority structures: their psychological parts and the structuring
relations between them. The partitioning of the mind that corresponds to priority
structuring, and the partitioning of the mind that, for example, captures, the accuracy
conditions of our mental states may cross cut.
18
See Wu (2014), Parasuraman, Warm and See (1998), and Oken, Salinsky and Elsas (2006). I am greatful to Wu’s discussion
for these references and for letting me get clear on the relationship between attention and vigilance.
19
This strategy is adapted form Dasgupta’s (2013) defense of comparativism about physical quantities.
100
The What and Why of Priority Structures
Consider the question whether the priority structure view of attention implies the
existence of non-propositional attitudes or non-propositional intentional mental
states.20
It is clear that the objects of attention are (almost) never propositions.21 The
metaphysical categories of the objects of attention, indeed, are extremely variegated.
They include the following: material objects, as when our subject is visually
attending to the tiger; locations in the subject’s environment as when she is visually
attending to a particular location in the sky; particular events as when she is attending
to a particular flash of light, or to a particular sound; on-going processes as when our
subject is attending to the candle’s flickering, or is auditorily attending to the rustling
of some leaves; then there are properties or features as when she is attending to a
certain color, a certain movement or a certain shape.22 Sometimes subjects also focus
their attention on certain facts: consider a case where our subjects return to her table
in the cafeteria after a short walk outside and her attention is caught by the fact that
her plate is now on the other side of the table, or – more dramatically – by the fact
that her laptop is not there anymore.23 And in thought, we attend to problems, issues,
ideas, but not to propositions. The psychological parts in a single priority system
indeed need not all be intentionally directed at objects of the same metaphysical
category (this, in fact, is the normal cases). Consider that if a subject is visually
attending to a material object, then a state of seeing that object will be strictly
prioritized over a state of seeing its properties (and the other way around when she is
attending to one of its properties, but not the object).
The psychological parts of a priority structure thus – almost always – are not
propositional attitudes, i.e. mental states where the subject is A-ing that p (e.g.
thinking that grass is green, or visually experiencing that this [tiger] is stripy and
moving fast towards me). If the object of the subject’s visual attention, for example,
is this tiger, then a psychological part that is intentionally directed at this tiger must
be of top priority. But if visually experiencing that this is stripy and moving fast
towards her were of top priority, then the subject would attend to the proposition or
fact that this is stripy and moving fast towards me. But she is not attending to this fact
20
See Watzl (forthcoming_a) for more discussion.
In English none of the attention constructions take that-clauses. In some other languages attention constructions do take that
clauses (thanks to Anders Nes for pointing me to this fact). Consider German: “Fritz lenkte/richtete seine Aufmerksamkeit
darauf, dass er dieses Glas in Rom gekauft hatte.” [Frinz directed/focused his attention on/to the fact that he had bought this
glass in Rome.] Similar expressions occur in the Scandinavian languages. Several other languages seem to be like that too (e.g.
Hebrew). To my knowledge, though, in none of these languages do attention constructions only take that clauses. Further, at
least in German the that clause constructions are relatively rare. Search in an important corpus of written German (Archiv der
geschriebenen Sprache “Alle öffentlichen Korpora” (available here: http://www.ids-mannheim.de/cosmas2/web-app/, containing
1.5 Billion words) reveals that “Aufmerksam(keit) darauf, dass” constructions account for less than 0.2 % of the occurrences of
“Aufmerksam(keit)”.
22
One might wonder about the exact metaphysical category here. Is the object of the subject’s attention a universal that can be
instantiated by many particulars, or is it a trope (a property instance)? Some psychological research suggests that at least
sometimes subject’s do not just attend to a particular property instance (the sofa’s redness) but that feature directed attention
spreads across the visual field (i.e. it spreads to the redness of other visually presented objects) (for a review see Maunsell and
Treue 2006). If that’s right, then that seems to put pressure on the trope theory of property directed attention (though we could
think of cases like this as cases of attending to some equivalence class of tropes).
23
See Farennikova 2012 for an extended argument to the effect that we can see absences like this (as Farennikova argues, we
need to distinguish these cases, where the subject sees something as an absence, from seeing something, like a shadow or hole,
that is in fact an absence).
21
How to interpret priority structures
101
or proposition, but to the object. So, the psychological part that is of top priority
cannot be a propositional attitude. It must be a mental state that is intentionally
directed at a material object and not at a proposition.
Insofar as we attend to entities other than facts or propositions (which is most of the
time), the priority structure view thus implies that there are non-propositional, objectdirected, intentional states. The occurrent mind is populated with those nonpropositional intentional states as the psychological parts of priority systems. And
indeed, in many cases, we have natural language names for the non-propositional
states that form the psychological parts of the subject’s priority structures (we can
talk of seeing something or hearing something).
Yet, while the priority structure view of attention implies the existence of nonpropositional intentional states, it does not imply that these non-propositional mental
states (or events and processes) are anything like the building blocks of a subject’s
priority structured mind.
The non-propositional psychological parts of a subject’s priority structure may, for
example, metaphysically depend on propositional wholes of which they are “divisive”
(or dependent) parts like Franz Brentano’s two hemispheres of a spherical indivisible
atom.24 These parts would exist in virtue of the fact that a certain whole exists and
facts about the structure of that whole.25 For comparison, consider a subject who
entertains a singular thought with the content that o is F. When a subject entertains
that thought she, arguably, refers to o and predicates F-ness of it. But from the fact
that entertaining a propositionally structured singular thought contains an act of
referring to a particular object as a part it does not follow that referring is a building
block of the mind, more fundamental than propositional thought. The referential act
may for its existence depend on the propositional act and its structure. It may be a
divisive part of a propositional thought.26
Similarly, a subject’s non-propositional activity of thinking about her next vacation
that forms a (top priority) psychological part of her intellectual attention toward that
vacation may depend for its existence on the fact that the subject entertains a variety
of propositionally structured thoughts about that vacation. Indeed, suppose that our
subject thinks a specific propositional thought, e.g. she is thinking that her vacation
will be in Paris. In having that propositional thought her intellectual attention may be
directed toward her vacation (this year it will be a vacation in Paris, not another of
those work trips), or toward Paris (not Madrid this year, Paris!). The propositional
thought then has non-propositional psychological parts. If the part that is intentionally
directed at the vacation (or the property of being a vacation) is of top priority, the
subject’s attention has the vacation as object. If, by contrast, the part that is
intentionally directed at Paris is of top location, it has a different object (Paris). The
24
Brentano, 1874/2012, p. 121 ff. For a discussion of Brentano’s mereology of the mental see Smith (1988)
For a recent discussion of how parts may metaphysically depend on the whole of which they are parts see Schaffer 2010.
26
I don’t intend to defend the view that reference is less fundamental that propositional thought. The point is merely to illustrate
a position
25
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The What and Why of Priority Structures
relevant psychological parts plausibly depend for their existence on the whole
propositional thought and its priority structure.
Intellectual attention thus arguably has non-propositional psychological parts that
depend on the propositional thought of which they are parts. If this is so, the arguably
something similar holds for perceptual attention. It does not follow from the fact that
the psychological parts of visual attention are non-propositional (we look at things
and not at propositions) that visual experience fundamentally is not a propositional
attitude. The priority structure view implies that visual experience has nonpropositional parts, but it does not imply that perceptual experience is build from
those parts (i.e. that the non-propositional parts are the most fundamental aspects of
perceptual experience). The priority structure view thus is neutral on the question
whether perceptual experience is a propositional attitude.
Generally, suppose that a subject has a certain mental state M. That very mental state
may have two structures. First, there is propositional structure. Propositional structure
partitions M into attitude and (propositional) content. This partitioning captures the
representational structure of M, and hence fixes the conditions under which M would
be accurate. Second, there is priority structure. Priority structure partitions M into
what its prioritized and what is deprioritized. This partioning fixes what the subject is
attending to. Either propositional structure or priority structure may be more
fundamental. Arguably, they are equally fundamental.
The psychological parts that occur in a priority structure of a mental episode are
better thought of as divisions within that mental episode, not as independent existents.
2.4
Priority systems: local or global?
After having considered the basic components of priority systems, let us consider the
individuation of the systems.
When, in the last chapter, I distinguished different forms of attention by what is of top
priority,27 I have neglected a second way forms of attention might be distinguished.
Different forms of attention may consist in a subject’s having several priority
systems.
Remember that priority systems were defined by a collection of psychological parts
that are priority connected. In a priority system everything is connected to everything
else by a path of higher, lower or equal priority. Do subjects have several or a single
priority system? If several, what are their contours?
Let us first get a little clearer on what exactly it would mean to have several priority
systems. A large priority system can often be decomposed into several smaller
priority systems. In this case, the larger system would be an extension of those
27
Visual attention corresponded to having a seeing at top priority, auditory attention was identified with having a hearing in that
top position (see Chapter 4 Sec. 6).
How to interpret priority structures
103
smaller systems, and preserve all their psychological parts and priority relations
between them. Even if the subject has a single priority system we may thus speak of,
for example, the subject’s visual priority system which will include only the subject’s
visual states. If the subject does have a single priority system, her visual priority
system will be a sub-system of that larger system. What I will mean by a subject’s
having several distinct priority systems then will be that for that subject there is no
priority system that extends all her other priority systems.
If there were several distinct priority systems, then the notions that I have defined in
the last chapter (such as top priority or distributed attention) always would have to be
relativized to a particular priority system. If we had two priority systems A and B, for
example, we would have top priorityA and top priorityB. Similarly, attention might be
distributed equally in A, but not in B. Two distinct priority systems may be disjoint,
i.e. have no psychological part in common, or they might overlap, i.e. have a common
psychological part. If priority system A and B would overlap then one and the same
psychological part x1 could be top priorityA but only of low priorityB. So, if a subject
had several distinct priority systems, then there would be many interesting theoretical
possibilities for how they may be related.
Do subjects have several distinct priority systems?
The considerations in the second half of this chapter concerning why subjects have
priority systems at all, i.e. to enable coherent action in light of behavioral decoupling,
will support the idea that there will be general, evolutionary, pressure for a subject to
have a single priority system, and not several distinct such systems. If subjects had
several distinct priority systems, then interference effects could arise. There may now
be two items of top priority and no way of resolving the conflict. This, in turn, may
lead to behavioral conflicts. But part of the evolutionary raison d’être of priority
structures, I argue, is to resolve such conflicts. In other words, if having priority
systems provides a subject with a whole subject way of organizing, integrating,
coordinating a certain mental life, then there should be some pressure towards having
a single priority system.
It has been argued, though, that in fact subjects have many distinct attentional
systems. I will now discuss these empirical findings and how they bear on whether
subjects have one or several priority systems.
Let us begin by asking whether subjects have a single visual priority system. It has
been suggested, in apparent conflict with the intuitive idea that there is such a single
visual priority system, that the two visual hemispheres may have something like
distinct attentional “resources”. For example, it has been shown that in multiple
object tracking scenarios subjects are able to attentionally track about twice as many
objects when these objects remain in their distinct visual hemifields as opposed to
when the objects cross the midline.28 Similarly, it has been shown that visual short
28
Alvarez and Cavanagh 2005.
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The What and Why of Priority Structures
term memory may increase when the items to be remembered occur in distinct
hemifields.29
Yet, these anatomical constraints on particular priority structures do not show that
subjects have two distinct priority systems for the two visual hemifields. They are
better viewed as specific constraints on maintaining multi-focal spatial attention.30
Feature based attention, for example, seems to be rather more integrated between the
hemifields.31 Overall, the data are most consistent with a single visual priority system
with hemispheric constraints on how many distinct items can be put at top priority
under certain conditions (dividing attention between the hemispheres makes local
spatial suppression easier, but not visual search).
What about the integration of priority systems across the sensory modalities? Alan
Allport and colleagues in 1972 provided what they called a “[d]isproof of the single
channel hypothesis.”32 They showed that so-called auditory speech shadowing (i.e.
orally repeating back pieces of speech that the subject hears) does not interfere with
sight-reading of piano music. In a task like this, auditory attention and visual attention
thus seem to operate relatively independently of each other. One might use results
like this to argue that there is a visual priority system and a distinct auditory priority
system.
Yet, again, the overall evidence is not consistent with that interpretation. Much is
known, for example, about cross-modal attentional interference effects: in the crossmodal Stroop-task the auditory presentation of a color word interferes with
processing of an incongruent visually presented color.33 The view with the strongest
support seems to be that there are brain regions (e.g. the anterior cingulate cortex) that
are specifically dedicated to cross-modal monitoring for conflict between a variety of
systems and biasing competition in line with overall task demands and goals.34 The
data thus again appear to be most consistent with a single perceptual priority system
whose specific shape is constrained by the computational systems it is engaged with
(dividing attention between modalities is easier cross modally than within a single
modality, and makes e.g. stimulus detection easier, but not identification).35
What about relativizing priority systems to particular tasks? It is a theoretical
possibility that subjects do not always have several distinct priority systems, but only
if they are simultaneously engaged in two unrelated tasks. In such a case, one might
argue, each task will have its own priority system, distinct from that of the other.
Maybe, then, there were two distinct priority systems in the subjects who performed
29
Delvenne 2005.
Alvarez, Gill and Cavanagh 2012.
31
Delvenne, op. cit.
32
Allport, Antonis and Reynolds 1972.
33
See e.g. Cowan 1989, Shimada 1990, Roelofs 2005. Similar crossmodal effects are found in other paradigms. See e.g. Spence,
Ranson and Driver 2000.
34
E.g. Botvinick et al. 2001; Botvinick, Cohen and Carter 2004.
35
See e.g. Bonnel and Hafter 1998. For a recent review of crossmodal attention see Spence and Santangelo 2009.
30
How to interpret priority structures
105
the speech shadowing and the sight-reading tasks in Allport’s 1972 study because
here the visual and the auditory task were unrelated.36
Yet, the priorities of at least most tasks do interact. Recent evidence suggests that
auditory and visual tasks do interfere: priority of one will tend to reduce priority of
the other.37 And it is well known that, for example, cell phone conversations while
driving lead to interference effects.38 Genuine multi-tasking (the simultaneous
performance of two distinct tasks) seems to be confined to cases where one task is so
automatic that it’s performance does not significantly draw on the subject’s capacity
for attention.39 Most cases of so-called multi-tasking seem to involve switches in
attention between two or more cognitive threads.40 In general there is now a lot of
evidence that the performance costs of switching between two tasks (or performing
them simultaneously) cannot be fully explained in terms of only interference effects
between the lower level underlying processes.41 Priorities between tasks thus
generally seem to interact, and so there is little evidence that subjects have multiple
priority systems for each of the tasks they are performing.
While the priority structure view by itself is neutral on the question whether we have
one or many distinct priority systems (it treats it as an empirical question whether we
do), there appears to be no clear evidence against the idea that subjects have a single
large priority system. In addition, as we will see in the next section, considerations
regarding the functional role of attention make it plausible that we do in fact have
such a full priority system. The full priority system will have many subsystems that
are somewhat independent of each other (i.e. how the priority structures in one of the
parts evolves over time is relatively independent from the priority structures in a
different part evolve). The overall shape of our full priority system is likely
constrained by the contingent architecture of the human brain, by task demands, and
much more. For some purposes it is thus convenient to speak of a subject’s visual
attention system or her intellectual attention system. The subject’s prioritization
though integrates these various systems, most likely resulting in complex priority
landscapes that reflect the subject’s complex perspective on the world.
36
An argument like this might draw on the arguments in Mole 2011.
Ruthruff, Pashler and Klaassen 2001.
38
For a review see Salvucci 2010.
39
Tombu and Jolicœr 2003 (though there is controversy. See Schumacher et al. 2001).
40
Salvucci op. cit.
41
See Rubenstein, Meyer and Evans 2001 for an in-depth review (cited also in Chabris and Simons (2010, p. 32) who say (in
accordance with what I take to be the dominant view) that “[a]s a rule, it is more efficient to do tasks one at a time rather than
simultaneously.”
37
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The What and Why of Priority Structures
3
The functional role of priority structures
3.1
Information pruning vs. prioritizing
Let us now turn to the role of priority structure. What is the point of having a mental
life that is priority structured? Just like we may ask why subjects have perceptual
capacities or the capacity for knowledge, so we may ask about why subjects
prioritize. An account of attention should show why attention is something worth
having.
So, why do we have the capacity for attention?
According to one popular view attention enables an organism to deal with capacity
limitations. We are bombarded with information from our environment and receive a
massive amount of input through our senses. But our brainpowers are limited – the
idea continues – and so we cannot process all of this information. We need the
capacity for attention to select some pieces of information for further processing and
disregard others. Which information we select partially depends on the type of input
we receive and partially on our current goals and interests. We may call this the
information pruning conception of attention.
The information pruning conception of attention is widespread among psychologists
and neuroscientists. Consider the following typical quotes.
Selection takes place in order to protect a mechanism of limited
capacity.42
The amount of information available for processing is always greater
than the limited capacity. Therefore the organism must process
information selectively.43
Reflected light carries too much information for the human visual
system to process at once.44
According to the information pruning conception attention plays the role of selecting
information in order to protect the organism from information overload. This general
view can take a variety of different forms. We have encountered some of them in
Chapter 1. Attention may, for example, be viewed as an information bottleneck or
filter.45 Views also differ as to which limited capacity attention protects. Some think
that the need for information pruning derives from the energy costs of brain activity.
42
Broadbent 1971, p. 178.
Garner 1974, p. 24. Quoted according to Van Der Heijden 1992, p. 242.
44
Franconeri, Hollingworth and Simons 2005, p. 275. Also cited in Lupyan 2015.
45
See Chapter 1 for references.
43
The functional role of priority structures
107
Peter Lennie, for example, calculates that given the amount of glucose available for
brain metabolism, less than 10 % of the cortex could be active at any given time.46
Others think that attention protects the brain processes associated with working
memory. Working memory is limited by its computational and neuronal architecture:
we can hold only about four chunks of information “in mind” at any given time.47
Attention is the gate that protects that limited capacity and prepares for and exports to
it only a limited amount information.48 Indeed, attention is sometimes itself viewed as
a limited resource to be variously allocated.49
As the last paragraph shows, the information pruning conception has often been
developed as a reductionist account, where attention is thought to be a sub-subject
mechanism or resource. Yet, while the information pruning conception naturally
lends itself to such a reductionist account, it need not be developed in this way. One
might, for example, take attention to be a form of subject level selection.50 On such a
view, attention would consist in subject level selecting of information for limited
capacity processing.
There is no doubt that our processing capacities are indeed limited.
But the view that the central function of attention is to protect these capacities is
problematic. Consider that, if the information pruning conception were right,
organisms with very small information processing capacities would have more need
for attention. As Gary Lupyan puts it in a recent paper
If humans with their relatively large memories and sensory processing
capacities are in need of attention to cope with all that information out
there, then consider how much attention an earthworm would need to
make sense of all that information!51
Yet, as Lubyan hints at, this prediction appears to be not borne out. Simple creatures
like the earthworm do not have and do not need the capacity for attention. This
remains true even for organisms like insects, whose sensors arguably receive much
more information than those of the earthworm. Attention is not necessary to deal with
limited capacities.
Conversely, the information pruning conception of attention also implies that
organisms with greater information processing capacities would have less need for
attention. Yet, this prediction also does not seem borne out. Consider what would
happen if our information processing capacities were much larger. Suppose, for
46
Lennie 2003.
E.g. Cowan 2000; Buschmann et al. 2011; Miller and Buschman 2013.
48
Prinz 2012.
49
Kahnemann 1973. Arguably this view is also present in our familiar ways of thinking of attention as something we can “pay”
to various things (see Doughney 2013).
50
This view might be modelled after Wu 2011, 2014. Note that Wu himself does not hold that attentional selection is due to
capacity limitation, but due to constraints on action. I will discuss the idea that attention is selection for action in Sec. 3.3 below.
51
Lupyan 2015, p. 561 Fn 11.
47
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The What and Why of Priority Structures
example, that 90 % instead of 10 % of the neurons in our brain could fire at any time
or that we had a working memory capacity of 400 chunks instead of four chunks. Or
suppose, to make things more extreme, that we had minds that could make use of the
information processing capacities of all the google servers in the world (indeed, some
argue that our minds already include such out-sourced storage and information
processing capacities: maybe our minds have been technologically super-sized, and
are now partially realized in exactly those google servers).52
Would we, if we had such super-minds, have no need for the capacity for attention?
The answer seems clearly: no. Life with the information on the google servers so
close at hand, has made attention more important, not less important. Information
processing power and memory storage need to be organized. Without organizing
large amounts of information this information becomes useless. If a subject has very
large processing capacities then she needs to assign priorities, distinguish what is of
relevance to her from what is not of relevance, and structure the information that is
available to her around those things that she prioritizes. The information stored on the
google servers is useful to us only because we can prioritize some of it at any given
time.
These considerations lead to a second general conception of the central role of
attention – the one that I would like to defend. This is the organizational conception
of attention. On the organizational conception the function of attention is one of
organizing the mind. The organizational conception can make sense of why the
information pruning conception might have been appealing. One way of giving
priority to a piece of information is to close the doors to those that are less relevant.
And so part of what it is to have a certain priority system consists in what is and what
is not in it. But keeping some information out is, of course, not the only way – and
often not the best way to organize information. It will often be good to remain
“aware” of what is temporarily deprioritized in order to bring it back to central
priority once the situation is changing. And often it will be useful to connect what is
not so relevant to what is, so as to help dealing with the top priority item (e.g. work
out at the gym so as to be focused when caring for your children).
Prioritizing also may require limiting how much you prioritize at any given time.
Giving too many distinct items equally high priority without treating them as a single
unit is likely to make those priorities useless and is likely to lead to interference.
Consider trying to give equal priority to writing a book, caring for your children,
making your love life work, training for a marathon, and learning how to play the
guitar. As you add more and more items to the top of your list, you may as well stop
prioritizing at all. Prioritizing is often useful only if it is limited and provides a clear
ordering. It must organize, integrate, and coordinate.
If attention is prioritizing we would expect that it often will look limited. And in a
specific organism architectural limits for how much can be given top priority may
52
See Clark 2008.
The functional role of priority structures
109
well have evolved. According to the organizational conception, our limited working
memory capacity, then, for example, is not an independent constraint that results in
our need for attention. Rather, limits in working memory arise from our need for
prioritizing: what is of top or high priority should be limited. Indeed, one should have
been perplexed by the idea of such a severely limited capacity in the first place: why
should an organism like us – whose brain seems to have evolved for high power
storage and processing – also have evolved a brain that enables the organism to hold
only four chunks “in mind”?53 Limited working memory thus arguably is an
adaptation to provide an architectural cap to how much an organism can keep at top
priority. Such a cap prevents interference effects.
3.2
Prioritization and behavioral decoupling
According to the organizational conception, the central function of attention is to
organize, integrate, and coordinate the various parts of the mind by means of
prioritization. But why do we have minds that must be organized in this way?
At the end of this book, I hope to have made it plausible that at least conscious minds
without attentional organization are impossible. Without priorities subjects wouldn’t
have a subjective perspective on the world, and without having a subjective
perspective on the world they wouldn’t have conscious experience. So, no subjects (at
least: no conscious subjects) without priorities. But to get there we still have a long
journey in front of us. At the end of this journey, I hope to have shown that we cannot
fully detach the functions of attention from what it is to have a conscious mind.
For now, I will take a very different route. Subjects need to prioritize in order to
achieve behavioral coherence in light of behavioral flexibility. This function of
attention has been stressed in work by Odmar Neumann, Alan Allport and Wayne
Wu.54 I believe that it is fundamentally on the right track. In this section, I will
provide my own way of spelling it out.
Neumann puts the central idea as follows.
[We need attention] to avoid the behavioral chaos that would result
from an attempt to simultaneously perform all possible actions for
which sufficient causes exist, i.e., that are in agreement with current
motives, for which the required skills are available and that conform to
the actual stimulus situation.55
While the earthworm has a highly limited repertoire of behavioral options, complex
organisms, like us, have behavioral flexibility. Given occurrent sensory input (“the
actual stimulus situation”), we are able to engage in a number of different forms of
53
See Baars 2000 for this point.
Neumann 1987; Allport 1987, 1990; Wu 2010, 2011, 2014.
55
Neumann 1987, p. 374.
54
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The What and Why of Priority Structures
behavior. We may call this behavioral decoupling.56 While the earthworm’s behavior
is directly coupled to a particular sensory input – much like reflex behavior is in us –
a more complex organism can engage in different forms of behavior in the same
sensory situation – behavior and sensory situation are decoupled. The resulting
problem is what Wayne Wu has called this the Many-Many problem (drawing on
ideas and terminology by Alan Allport): given many different inputs an organism
faces many different behavioral options.57
The idea, then, is that in light of behavioral decoupling the organism needs to assign
temporary priorities so as to avoid performing all possible actions simultaneously and
hence “behavioral chaos” (Neumann, op. cit). The need for prioritization thus arises
only for organisms with behavioral flexibility (and thus the earthworm has no need
for attention).58
Neumann, Allport and Wu sometimes write, as if behavioral decoupling is an
independent “problem” (the many-many problem) to which attention provides the
solution. In my view, attention is part of what enables behavioral decoupling.
Consider a simple organism that encounters sensory solicitations, i.e. it is pulled to
perform a certain behavior directly on the basis of a certain sensory stimulation (think
of bacterial tropisms where, for example, a sensory registration of light is directly
translated into swimming behavior). In an organism without behavioral decoupling
there are hard-wired mechanisms that decide which behavior will result given a
certain stimulation. While presence of light in the absence of food will result in
swimming behavior, in the presence of food feeding behavior will result instead. But
now suppose that a slightly more complex organism is able to temporarily prioritize
the registration of light, and temporarily deprioritize the registration of food based on
both the incoming sensory information as well as its current needs. Now it is able to
act flexibly: now the same sensory information is compatible with several (in this
case two) forms of behavior. If the organism’s needs were to change, it could react
differently to the same sensory situation. In order to gain this behavioral flexibility
the organism cannot fully discard the temporarily deprioritized aspect of the sensory
situation. What is deprioritized must be kept “live” so that were the organism’s needs
to change, its behavior could change. The non-decoupled organism did not have a
many-many problem, and thus did not need a solution. The organism that prioritizes
has a many-many problem, but also a solution. It gets behavioral flexibility by having
the capacity to prioritize in a way that integrates its motivational state with its sensory
situation. And this is exactly what attention does.
Prioritization thus allows for a simple form of behavioral decoupling: it is a
decoupling that is achieved without separating “representation” from “motivation.”
Priorities do not by themselves represent and they do not by themselves motivate. The
behavioral decoupling thus is simpler than the one achieved through standing states
56
See Godfrey-Smith 1996 and Stereley 2003 for a similar use of this term.
Wu 2010, 2011, 2014.
58
In complex organisms that have persistent beliefs, desires, motives and skills it often will also be the case that many actions
are consistent with the agent’s background motivation and representation of the world.
57
The functional role of priority structures
111
such as preferences or beliefs.59 Prioritization happens on the fly, with regard to the
subject’s current mental life. Beliefs, preferences, and intentions, by contrast, concern
the organism’s (dispositional) setup and require cross-temporal organization (they all,
arguably, function to enable certain forms of stability, and hence intrinsically resist
easy change).60
Note that our slightly more complex organism does not – and does not need to –
select a particular behavioral option. It simply prioritizes some sensory stimulations
over others. In the case we are considering, the sensory stimulations are soliciting,
and so by prioritizing one over others a particular behavior results. Yet, once an
organism has actual visual representations of its environment – ones that represent
distal properties and objects – prioritizing a particular aspect of those visual
representations will normally not yield a particular behavior. Which behavior results
will depend on what else the organism perceives, as well as on its motivational state.
Suppose, for example, that our organism assigns priority to a certain visually
represented piece of food. It ‘keeps an eye’ on it (a simple analogue of visually
attending to that piece of food). A number of behaviors might result. If the organism
is currently hungry it might start to engage in eating behavior. If it is not currently
hungry it might start to engage in storage behavior – digging a hole to store the food
in. If strong competitors are around, the organism might just keep watching the piece
of food while at the same time fending off the competitors (the last two examples
show that prioritizing a visually represented item need not lead the organism to act on
it at all).
My suggestion then is that attention is such a general purpose way of prioritizing:
assigning priorities in a way that interacts with the whole organism’s motivational
system and the sensory situation, and in a way that is not tied to particular forms of
behavior. A central function of attention is to enable behavioral decoupling. It
provides a priority organization that is neither directly tied to how the organism
represents the world around it nor directly tied to what it is motivated to do. To have
such an organization gives an organism behavioral flexibility.
3.3
Prioritization and selection for action
I would like to end this chapter by comparing the priority structure view to an idea
defended in recent work by Wayne Wu. According to Wu the best answer to the
question “What is attention?” is that “S’s attention to X is S’s selection of X for
action”.61 The idea that attending to something consists in selecting that thing is
certainly highly natural. It seems close to the claim that attention prioritizes.
According to the attention as subject level selection idea, attention is individuated by
its functional role: its role is to select some items for mental or bodily action.
59
Godfrey-Smith 1998; Sterelny 2003
See Holton 2009.
61
Wu 2014, p. 85.
60
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The What and Why of Priority Structures
So, is prioritizing just selection for action?
No, and the view that attention is subject level selection for action is problematic for a
number of interconnected reasons (going through these reasons helps to bring out
again several aspects of what motivates the priority structure view).
First, note that, as I have argued in chapter 2 and 3, (perceptually) attending to
something is itself a mental activity – one that we sometimes perform voluntarily and
intentionally. In particular, I have argued that listening to something, looking at
something and watching something are perceptual ways of attending to something.
An agent who is listening to something or watching something does not need to do
anything else. Particular stretches of an intentionally performed activity of listening
or watching will be intentional actions. But now the view that attention is selection
for action faces a dilemma. On the one horn of the dilemma, consider that the
selection for action view accepts that attending to something may consist in selecting
that thing for attending to it. In this case, the account becomes problematically
circular (you must already engage in the action before you can engage in it). On the
other horn of the dilemma, consider that the selection for action view excludes
attending from the range of actions that attention is selecting for. Given that the
selection for action view includes mental actions among those that attention is
selecting for62 – and it arguably must do so in order to be plausible – this move seems
ad hoc. Further, if attention were selection for non-attending actions, then weather
watchers (i.e. creatures who only engage in perceptual action but no bodily action or
reasoning) would be metaphysically impossible: these creatures do not watch the
weather in order to select it for any non-attending action. But weather watchers do
seem evidently metaphysically possible (I here agree with Galen Strawson (1994)).
Thus, selecting something for non-attending actions is not necessary for attention.
The first argument against the selection for action view thus is that it cannot explain
that attention itself is sometimes an action.
A second (and related) problem with the view that attention is selection for reasoning
and action is that it reverses the intuitive direction of explanation: often you are only
able to select an object to reason about it or act on it, because you have focused your
attention on it. Consider focusing attention on the sound of a saxophone. It is quite
plausible that because her attention is focused on the sound of the saxophone it is
available for the subject to select it as something to think about. Attention to the
sound plays an explanatory role: it in part explains why she is able to select the sound
as target of her reasoning. But attention can play that explanatory role, only if it is not
identical to selecting the sound for reasoning.
A third problem is that selecting for action is not sufficient for attention. Consider the
following. While engaged in a conversation over dinner and while your (perceptual)
attention is focused on your conversational partner you might reach for your glass to
drink. You might be aware of your reaching as well as peripherally conscious of the
glass. You are selecting the glass as the target of a bodily action. Yet, you can do this
62
Wu 2014, p. 86
The functional role of priority structures
113
without focusing your attention on the glass. There may be attentional processes
involved in your reaching for the glass, but you do not need to attend to the glass.
Similarly, consider coming home and switching on the light in a familiar room. Again
you might be peripherally conscious of switching on the light (as well as being
peripherally conscious of the switch). You are selecting the light switch as the target
of your bodily action. But again, your act of switching on the light might be so
automatic that your attention need not be focused on the light switch. You might also
be reasoning about what you are not attending to. While your perceptual attention is
focused on your conversational partners, you might unconsciously or peripherally
reason about or assess their socioeconomic status. Such assessments are known to
shape who will be the focus of your visual attention. But the socioeconomic status is
not the focus of your attention. 63 You have selected that status for reasoning about it
(who else could have selected it?), but you are not attending to it. There is peripheral
reasoning as well as unconscious reasoning. For those attention is not necessary (the
claim that attention is necessary for focused reasoning, of course, is trivial). These
counterexamples show that selecting something as the target of reasoning and bodily
action is not sufficient for attention.64
A fourth problem is that selecting and attending have different temporal shape.
Attending, as I have argued in chapter 3, is an on-going uncountable process and not
a countable event. You may attend to something for a certain period of time, and it
does not make sense to ask how often you have attended to, say, the glass in front of
you during the last hour. By contrast, selecting something as the target of reasoning or
action is a particular datable and telic event.65 Necessarily, if you are selecting
something to act on it, then you have not already selected it. By contrast, it is at least
possible (if not necessary) that if you are attending to something, then you have
already attended to it. One can count how many times you have selected something in
a particular period of time. By contrast, one cannot count how many times you have
attended to that thing.
The fifth problem for the selection for action view is that it has a hard time explaining
that there can be degrees of attention, as well as cases of distributed, divided or
diffuse attention. As we have seen, sometimes attention is equally divided between
several – often unrelated – objects or features, and sometimes attention gets equally
distributed across, for example, the visual field. But how would the selection for
action view account for any of this? Selection does not seem to come in degrees.
Either you are selecting something or you are not; you are not selecting one thing
more than another. And what happens if you are attending equally to the whole visual
field: are you selecting everything for action? There may be some ways of finessing
the selection for action view to deal with such problems, but the intuitive idea that
attention selects a target for some action like grasping, pointing etc. is called into
question.
63
Foulsham et al. 2010;
For a similar criticism see Mole, 2005, p. 44-46.
65
See also White, 1963, 1964.
64
114
The What and Why of Priority Structures
There is a common diagnosis for why the selection for action view leads to these
problems. What is plausible and correct is that one of the central functions of
attention (plausibly tied to its evolutionary origin) is to enable flexible action in
behaviorally decoupled agents. But the step from this idea to the claim that attention
just is selection for action is implausible and unwarranted. What is right is that
attention prioritizes certain items over others, a priority structure that can – in normal
human agents – be exploited in various forms of action. These attentional priorities
can exist even in agents who cannot exploit them such as the weather watcher (maybe
such agents would never evolve, but they are possible). Priority structures explain
why the agent selects certain courses of action (they are not identical to the selection).
Priority structures are important for some forms of selecting targets for bodily action,
but not all (as in the case of unattended selection). Prioritizing – unlike selection for
action – can go on for a certain period of time leading to persistent priority structures.
And finally priorities can come in degrees, and you might give equal priority to
everything in your visual field – as in distributed attention.
The priority structure view thus can explain what motivated the selection for action
view while avoiding its problems. It is the view that is best motivated by taking
seriously the central functional role of attention. Attention makes information (and
other things) useful to the agent, and it plays a central role in the explanation of
flexible action, but it is not selection for action.