Reid’s Discovery of the Sense of Balance
David Vender
When we speak about the senses we usually mean the ive traditional senses, but
even a slight acquaintance with the scientiic research on sense perception tells
us that the simplest questions about the senses are currently open questions.
What is here meant by the simplest questions are how many we have and
how they should be counted. If there are no good answers to these basic
questions, or at least a fairly broad agreement on how to proceed, then we
don’t really even know what a sense is.
Until recently there was little concern about the senses in philosophical
discussions and when they needed to be mentioned the old list of ive was
offered or, more simply, vision was enlisted as a paradigm of all perceiving and
the problems of vision tended to be discussed as if everything said applied
across the whole sensory range. This is easily checked and there is no need to
go into examples. It is fair to say that this substitution of vision for perception
is not always incautious or misleading, but it has been very widespread.
All this is now changing. Debates are emerging about the counting problem
and the problem of the individuation of sense modalities, which is the closely
related problem of separating the senses.1
There are various currents in these debates and it would take some time
to go into even the main issues but the aim here is to point out the danger of
missing an important opportunity by neglecting to pay enough attention to the
most remarkable, the most fundamental sense. This is the sense of balance.
Two things should be made clear. Firstly, what Thomas Reid can tell us
about balance and, secondly, how important and astounding balance is. Reid is
not generally cited as a contributor to our understanding of balance. Perhaps if
one is looking at the senses from a physiological or psychological perspective
then his remarks are a bit thin, but looking at what he said in the context of
the philosophy of perception is very worthwhile indeed.
So in outline we irst look at the senses and the discovery of balance, then
review what Reid said about balance, how it its into the historical picture
1
See F. Macpherson (ed.), The Senses: Classical and Contemporary Readings (New York,
2011).
2
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and what the crucial points for us now are. After that it is best to catch up
with some of the comments about balance in the current debate about the
senses. There are some peculiar things said about it and Reid can be asked
to help us sort out some of the muddles. Finally, a suggestion or hint from
Reid will be taken up in order to show that the point about balance being
the most fundamental sense – maybe it is better to say that it is foundational
for all perception – is not just grandstanding. This will be illustrated by a few
empirical results from the scientists looking at balance.
The Discovery of Balance
We all know what balance is. If you lose your balance you fall over. If you drink
too much wine you get wobbly and walking becomes a bit precarious. There
are also some terrible aflictions which cause the sufferer to be incapable of
orderly movements or even make them unable to stay stable. But is balance
really a sense?
Asking this question immediately complicates matters but speaking
generally we might expect that to count as a sense there should (a) be an
identiiable organ or set of organs, (b) when this is working properly we use
it to obtain some speciic information about the physical world, and (c) that
our possession of this information is not merely inferred indirectly but that it
actually informs or at least plays into our direct experience of the world. These
may not be separately necessary and jointly suficient criteria and each can be
debated but it is a reasonable starting point.
A question now arises. If balance is indeed as important as has just been
said, why has it not been counted among the senses? Why have humans
walking and falling over for millennia and developing all sorts of cultures
failed to notice it? Three reasons which reinforce each other can be suggested.
Firstly, starting with experience, it is a fact that when everything is going
well there is little to be distracted by in our bodily balance. We notice when
we are about to topple over, we get miserable when seasick or suffering from
vertigo, but generally speaking balance is a pretty quiet sense. If we feel
anything while going about daily routines then we hardly notice it and how
it plays into experience is more subtle than seeing colours or hearing sounds.
Secondly, the organs are well hidden. It is not even clear where they might
be. Most of the parts of the body have some role in maintaining posture so
it is not obvious where one should look for organs – even if, like touch, it is
Reid’s Discovery of the Sense of Balance
3
a distributed sense with receptors all over the body. As it happens there is
a localised set of relevant organs but scientists now rarely speak of a sense
of balance since that needs several co-operating systems. Arms and legs
and feet and muscles and joints are all needed to maintain posture, but the
keystone holding this elaborate frame up is not in the muscles or joints. A
most important piece of the puzzle is the vestibular apparatus hiding in a thick
piece of bone behind each ear.
It is a complicated organ which transduces the direction of the resultant
force from gravity and linear acceleration, as well as rotations around the three
orthogonal axes in space. Since it is so close to the inner ear there might be
a temptation to think that it has something to do with hearing. Even if that
mistake is avoided, one needs to know quite a bit of physics to understand how
it works. It is not too much to say that before the physics of Galileo and Newton
it would have been a struggle to unravel the mystery of its basic workings.
Thirdly, all the important functions and malfunctions of the vestibular
apparatus seem to point to this organ as something which is important to
the individual, much as the heart or liver might be. To count as a sense for
the naive understanding the organ must be pointed outward, it must tell us
about external objects. Pain and hunger are private and not counted along
with the ive. Similarly, motion sickness and even the ordinary feel of walking
have more to do with individual vigour, itness and disease than with sensory
perception as traditionally understood.
These three reasons seem suficient for not counting balance as a sense.
As it happens the naive understanding is quite wrong in trying to make a neat
division between our bodily sensations and what the Aristotelians used to call
the ive external senses, but to see this one needs to look at how the role of
the vestibular apparatus was clariied.
Among the important names usually associated with the history of
vestibular research are Ernst Mach, whose philosophical fame rests largely
on psychophysics and his radical relativism, Jean Pierre Flourens, the famous
physiologist who described the organs, and Jan Purkyně, who examined vertigo
after rotation.2 These are all igures from the nineteenth century but Nicholas
Wade from the University of Dundee has looked at the early history and there
2
Some of the history is covered in J. E. Hawkins and J. Schacht, ‘Sketches of Otohistory
Part 8: The Emergence of Vestibular Science’, Audiology and Neurotology, 10 (2005),
185 – 190, and N. J. Wade, ‘The Search for a Sixth Sense: The Cases for Vestibular,
Muscle, and Temperature Senses’, Journal of the History of the Neurosciences, 12 (2003),
175 – 202.
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is an unsung hero there.3 William Charles Wells was a contemporary of Reid
and he deserves the lion’s share of the credit for the early experimental work
on how rotation affects our vision.
The point to notice about much of this early work connected to the
vestibular organs is that it is not actually about the sense of balance. It is really
about vision and how our vision depends on movements and accelerations.
The subjects of the experiments on vertigo and nystagmus following rotation
were either strapped to a chair and spun about or simply turned till they got
dizzy, as children like to do.
If our main interest is in normal healthy balance then these performances
are only a small part of the story. They tell us a lot about the interactions and
conlicts between vestibular function and the vision system, but little of direct
signiicance about balance and especially agency. To understand the basics of
balance, it is better to see what Reid had to say.
Reid’s Remarks on Balance
Reid’s explicit remarks on balance occur in a late essay on voluntary motion.
This essay appears in the collection called Thomas Reid on the Animate Creation
edited by Paul Wood.4 The essay is called ‘Of Muscular Motion in the Human
Body’ and it was read before the Glasgow Literary Society in 1795.5 By the
way, Wells published his Essay on Single Vision With Two Eyes with a description
of the experiments on vertigo in an appendix in 1792.6 Wells of course knew
of Reid and made some comment on Reid’s ideas on vision from the Inquiry.7
This is what Reid said on balance:
This Power we have of perceiving the ballance of our Body is so like to
our other external Senses, that it might very justly have been accounted
3
4
5
6
7
See N. J. Wade, ‘William Charles Wells (1757 – 1817) and Vestibular Research Before
Purkinje’, Journal of Vestibular Research, 10 (2000), 127 – 137, and N. J. Wade, Destined
for Distinguished Oblivion: The Scientiic Vision of William Charles Wells (1757 – 1817) (New
York, 2003).
P. Wood (ed.), Thomas Reid on the Animate Creation (Edinburgh, 1995).
Ibid., 28.
Wade (2000), 130 – 1.
Giovanni Grandi has pointed out to the author that among Reid’s manuscripts there
are notes showing that Reid read Wells’ essay in June 1792. There are no comments
on the appendix.
Reid’s Discovery of the Sense of Balance
5
a distinct Sense, if it had been so much relected upon as to require a
Name.
In each of the external Senses, there is an Impression made upon the
Body or on some part of it, which by our constitution produces a
certain Sensation of the Mind, and that Sensation is by our Constitution
accompanied with the Perception of something external.8
He also remarked on the importance and excellence of this sense:
When we observe with what ease, and Grace those Motions are
performed by those who are expert, and compare them with the
Laws of Motion, we must be convinced that this Sense by which we
perceive the least deviation of the Body from its Ballance, may by Use
be brought to a degree of Accuracy which is hardly to be observed in
any of our other Senses.9
Contained in these remarks are tremendous insights about the senses,
especially if we pay attention to the context, which is a discussion of voluntary
movements. Here is just a little more:
This sense of Ballance may be seen in a Child of two or three Months
old. If sitting upon ones knee he begins to tumble, he immediately
starts & endeavours to recover himself. But it is greatly improved
by Use, in every Employment that requires its exercise … This sense
of our Ballance is produced not onely by the impression made by
the power of gravity but by any other Force which endangers the
Ballance.10
Reid does make some remarks on vision in the same essay, but these are
mainly to do with directing the eyes by means of the antagonist muscles – so
he speaks of a balance in the nervous power of those muscles – rather than
the cross modal effects studied by those investigating vertigo and imposed
8
9
10
Wood (1995), 110. Reid is here explicitly afirming that the workings of balance are
consistent with his epistemological scheme and his distinction between sensation
and perception.
Ibid., 111.
Ibid., 111.
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accelerations. He is primarily concerned with how active agents use the
muscles and notes that:
There are however many voluntary Motions in which some previous
Perception of the Understanding is necessary to direct us to the Motion
which the occasion requires.11
Not only must we sense how muscles move, muscular exertion is the default
state:
Although all voluntary Motion is performed by the Contraction of
Muscles, we must not from that conclude that when no Motion is
willed, the Muscles are inactive. The Exertion of Muscles is no less necessary
to rest than to Motion. In every position of the Body excepting perhaps that of
lying prone The reason of this is that there are so many Articulations
in the Limbs, & in the Spine & Neck and these in a living Body have
such Lubricity to facilitate their Motions that without the Exertion of
Muscles, it would sink down to the ground like a Chain of many links.
So we see a Man does if he is struck dead or deprived of all power of
Muscular Motion in an instant.12
Wells, and Reid’s Main Points
As already mentioned, a few years before Reid’s remarks William Charles Wells
published an essay on vision. In an appendix called On Visible Position, and
Visible Motion Wells speaks about balance. He starts by noting that:
In the estimates we make by sight of the situation of external objects,
we have always some secret reference to the position of our own bodies,
with respect to the plane of the horizon; and from this cause, we often
judge such to be at rest, whose relative places to us are continually
changing; and others to be in motion, though they may constantly
preserve, in regard to us, the same distance and direction.13
11
12
13
Ibid., 110.
Ibid., 112, emphasis original.
W. C. Wells, Two Essays: One Upon Single Vision with Two Eyes; The Other on Dew
(Edinburgh,1818), 69.
Reid’s Discovery of the Sense of Balance
7
The concern here is with judgment of visible motions. Wells talks explicitly
about bodily balance a little further on, saying:
What is there within us, to indicate these positions of the body? To
me it appears evident, that since they are occasioned and preserved by
combinations of the actions of various voluntary muscles, some feeling
must attend every such combination, which suggests, from experience
perhaps, the particular position produced by it. But in almost all the
positions of the body, the chief part of our muscular efforts is directed
toward sustaining it against the inluence of its own gravity. Each
position, therefore, in which this takes place, must be attended with a
feeling, which serves to indicate its relation to the horizontal plane of
the earth.14
Wells then immediately considers how it is that we see objects to be still
despite irregular motions of the body such as are experienced on a ship rolling
and pitching. The point is that Wells is really interested in visible position and
motion and how perception of these relates to bodily motions. Reid in his
essay is not particularly interested in the perceptions of sight but in the control
of bodily movements themselves.
Three of Reid’s crucial points are:
1) Voluntary movements and eforts maintain balance and posture. he
implication here is that this sense is active in that we participate as agents
in generating the sensations felt. he perceiver and the actor are one and
the same and if we wish to entertain a passive model of perception such
as placing the perceiver in a Cartesian theatre then we have to allow
them to get onto the stage because without their activity and participation the show simply does not go on.
2) his sense has its own sensations. Without getting into the details of Reid’s
views on sensations two remarks are appropriate. Firstly, these sensations
are bodily sensations associated with muscles and Reid did associate balance closely with muscular sensations. Secondly, these sensations are
normally subliminal unless we are in imminent danger of falling or are
14
Ibid., 70.
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pushed and need to act decisively to restore our balance. As Reid might
have said, we normally pass over these sensations unnoticed and attend
to our other perceptions as we pursue our goals. hat does not mean
that we are not doing anything in keeping balance. In fact we are always
acting and the sensations informing us of posture and movement are
always present.
3) here is evidence of development. Watching infants and young children
rather than normal adult functioning is helpful. Infants spend much
of their time trying to orient themselves and to control their movements. he triumph of this development is getting mobile, particularly
in standing up and walking. Even later we can become more skilled in
performing various motions.
There is no need to play Reid off against Wells in a competition on these
points. Wells made closely related remarks. Here is an example:
Should the necessity of supporting the body against its gravity, by the
actions of our voluntary muscles, be suspended in whole, or in part, our
judgments of the situation of objects, with respect to the horizon, must
become irregular and uncertain, notwithstanding any general habit we
may have acquired from experience.15
The main reason why what Reid tells us is exceptional comes from a fourth
point and that is his remark that we should compare our achievements to the
Laws of Motion and count the sense of balance as an additional sense. That
is a very ine suggestion because it challenges our ideas about what a sense is.
Why has balance not been counted as a sense? The simple answer to
this, as suggested earlier, is that the traditional count separates the perceiver
from the world. Information about our own body, however it is acquired,
is separated from perception of external objects and their qualities and
properties. The count is conservative in that only those perceptions for
which it seems easy to draw the line between the objects in the world and
ourselves are given to our senses.16 This separation is not easy for sensations
of pain or of warmth and so we do not traditionally count senses of warmth
and pain.
15
16
Ibid., 73.
This conservatism is now still relected in calling bodily sensations private as, for
example, Armstrong does when separating the perceiver from the surrounding
world. See D. M. Armstrong, A Materialist Theory of Mind (London, 1968), 307.
Reid’s Discovery of the Sense of Balance
9
Motions, as it happens, also seem to separate easily into motions of our
body and motions of external objects perceived mainly by sight. But we do not
traditionally count a sense of motion because perception of the motions of
objects is already attributed to the sense of sight and when we feel motion by
touch then it is not separate from the motion of our body and the boundary
between active and passive moving is inconstant and dependent on attentive
involvement. Applying then the conservative approach it can be said that
feeling movements by touching objects is more like interacting with hot and
cold objects than it is like watching passively the movements of objects in
space. Hence a sense of bodily motions was not traditionally counted.
This naive separation of the senses from the perception of self evidently
did not impress Reid who took the direction of gravity to be external even if
we do come to know it primarily by way of sensations within our body. It is
interesting that where Reid speaks of ‘external’ Wells writes about ‘sustaining
[the body] against the inluence of its own gravity’.17 In any case the naive
separation does not survive critical relection. When we look at the laws of
motion, even in the context of Galilean relativity, then the separation of selfmotion from motion of objects is not simple after all. It is wholly ambiguous.
Even locating stationary objects in space inevitably implicates the perceiver
in a relation, just as sticking a cold hand into warm water tells us about the
interaction rather than about the absolute temperature of the water.
In one way there does seem to be a natural division of movements. This
is the division between moving and being moved. As just mentioned this is
complicated by the fact that motion is not always attended to, especially in
habitual movements or the skilled movements that we are inclined to call
‘effortless’, and deliberate movement brings in further complications because
we cannot conine ourselves to kinematic descriptions – moving body parts
deliberately is always dominated by force and friction, resistance and strain.
These are the quantities of dynamical descriptions and dealing with them
explicitly can only be avoided by resorting to vague discussions of ‘motion’ in
the abstract while hoping that an imprecision in describing the phenomena is
inconsequential.
If the sensory separations involving motions are to be made systematic,
everything is found to depend on accelerations and with those on efforts,
muscular strains and voluntary movements. We are speaking not simply of
spatial relations and movements of constant speed but about dynamics, with
17
Wells (1818), 70.
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force, inertia, friction, acceleration, velocity, distance and duration all involved.
It is important to notice this: moving the parts of our body is more a question
of directed effort and acceleration than it is of translation, and the physics of
those movements feels more Aristotelian than Newtonian.
Before saying a little more about dynamics and how the sense of balance
provides the clue that is needed to understand how the separation between the
perceiver and the world implicit in the tradition is unworkable, it is instructive to
glance at the modern philosophical debate on the individuation of the senses.
The Current Debate
In looking at the recent discussion of the senses in philosophy it is apparent
that the main concern is with how one should reconcile the discoveries of
science, particularly physiology, psychology and more recently neurobiology,
with traditional philosophical arguments about perception. In particular,
the question is how the senses should be counted and what the meaning of
the tradition of ive is. An important early contribution is from Grice who
considered speciic criteria for counting and the search for and analysis of
criteria has been central to the continuing debate.18 Brian Keeley has recently
suggested that philosophers should follow the lead of neuroethologists – the
scientists who study the sensory endowments of exotic species such as the
star-nosed mole and the pit viper. Keeley’s main point is that sensations can
be safely ignored when we differentiate the senses or try to decide what is or
is not a sense.19
This idea that sensations do not tell us anything useful about our senses is
not conined to materialists such as Keeley and it would seem to be a dificult
thesis to defend against common sense views. Reid has a lot say which is
relevant, but the present topic is not the role of sensations in general but the
importance of the sense of balance so what has recently been said speciically
about balance needs to be looked at. However, one important consideration
must be kept in mind.
Reid and Wells worked far too early to have known the various functions
of the vestibular apparatus. Nowadays everyone who discusses orientation
18
19
H. P. Grice, ‘Some Remarks about the Senses’, reprinted in R. J. Butler (ed.) Analytical
Philosophy, First Series (Oxford, 1966), 133 – 53.
B. L. Keeley, ‘Making Sense of the Senses: Individuating Modalities in Humans and
Other Animals’, The Journal of Philosophy, 99 (2002), 5 – 28.
Reid’s Discovery of the Sense of Balance
11
and balance must be aware of its importance, but when we consider what Reid
wrote he was evidently talking about a multisensory modality in what he called
the sense of balance. Putting this negatively, he still had it mixed up with the
muscle sense. Putting it more positively, he was considering an endowment in
which both proprioception and vestibular functioning play a role. The relevant
sensations are what I would like to call compound or complex sensations. To
give an example of what this means by using colour, what is sensed is not
simply ‘red’ but that colour just over there which has just been noticed and
may now be fading or changing hue and must certainly contrast with other
colours in the ield of view.
With this in mind it is important to notice two aspects of what is said
about vestibular functioning at the present time. The irst is that the vestibular
apparatus provides no speciic sensations.20
Now a sense without sensations would seem to have no place in Reid’s
epistemology, and it needs to be asked what the vestibular apparatus could
do for us if it does not somehow contribute to our subjective experience.
As it happens it is not dificult to see what an organ which transduces the
direction of gravity and a set of organs which transduce angular accelerations
in the three orthogonal directions of space can do. They provide direction and
perspective. They do so by breaking the symmetry of purely relative spatial
relations in ixing a dynamical ‘downward’ as well as the directed rotations
around the up-down, front-back, and left-right axes of the head. Hence they
give us a reference frame and even what might be called, in the context of
dynamics, an ‘absolute here’.
Directionality and place is thus potentially available for all sensations if this
information is integrated with other sensations and feelings, giving them not
just their relative ‘thereness’ but ixing the human frame with respect to the
frame of reference of the Earth with its universally shared up and down, thus
making it possible to gauge the locations and the relative motions of not just
body parts but also external objects.
This role of the vestibular organs in giving directionality and a ixed
reference to all sensations can be considered initially as a speculation.
Before seeing where it leads there is the other important aspect of vestibular
functioning to be noticed. It arises in discussions of how many senses we
20
D. E. Angelaki and K. E. Cullen, ‘Vestibular System: The Many Facets of a Multimodal
Sense’, Annual Review of Neuroscience, 31 (2008), 125 – 50. F. A. Geldard also makes
this remark in The Human Senses (New York, 1972), as does W. von Buddenbrock in
The Senses (Ann Arbor, 1958).
David Vender
12
count and how our own activity in using the relevant organs contributes. Two
examples will serve to illustrate the issue.
Firstly, Brian Keeley considers a suggestion made by Anthony Kenny and
David Armstrong that part of what we mean by perceiving is the awareness of
moving and using an organ to get information. Keeley writes:
Armstrong proposes … that sense organs are bodily structures that we
actively use to gain information about the world, as when we open and
move our eyes to see or cock our head to hear. But he continues, this
runs up against the problem that we do not actively move organs in
all the putative cases of sense. For example, we do not do anything to
gain vestibular information. It seems to be ever present (which might
explain why Aristotle did not remark upon it). The use of an organ in
active perception does not seem to be of help here.21
Armstrong in fact does not mention balance or the vestibular apparatus and
does not seem to be interested in orientation in the relevant books dealing
with bodily sensations, but from what Reid and indeed Wells have been
telling us it is easy to see how mistaken Keeley’s comment is. If we wish to
collect vestibular information then it is actually what we do and do all the
time that matters. If we simply lie down and make no effort then orientation
can eventually be lost.22 It is also because the collection of this information
as part of our efforts is ‘ever present’ that allows it to serve as the basis for
the intentionality of our voluntary movements. These are intentional in the
sense that they have a goal and a desired direction. If we had no up-to-date
knowledge of the direction to the objects which we wish to reach, there is no
way we could reach out to them.
Since Keeley’s advice is to ignore sensations entirely it is not surprising that
he considers the ‘awareness of organ use’ criterion only to replace it with the
idea that considering the anatomy, wiring and dedication to a function of the
organs is enough. To see the view I am disputing actually espoused, we need
to turn to John O’Dea who says that:
21
22
Keeley (2002), 13.
This should not be taken to imply that relaxing or reducing the effects of gravity by
immersion in a lotation tank will quickly lead to disorientation. The connections
between attention, habit, action and stimulus are complex. Orientation, as well as
proprioceptive knowledge of the extent and position of bodily parts, are in some
ways remarkably robust but at the same time surprisingly fragile.
Reid’s Discovery of the Sense of Balance
13
It is an odd fact that some rather obvious senses were never included in
the traditional ive. The account I’m proposing can explain this, in the
following simple way: that in these cases there is no feeling of using any
sense organ at all. The most vivid examples of this are proprioception
and the senses of balance. … with the sense of balance; you don’t
need visual, tactile, or any other cues to know which way the ground is.
But there is no part of the body that we’re aware of using to ind that
information out. If my account is correct, it makes sense that these
were never counted as sixth or seventh senses.23
It is always debatable just how much we are aware of, but by paying attention
to what Reid said about our sense of balance we can see what is wrong here.
It is closer to the truth to say that with the sense of balance it is every part
of the body that we’re aware of using to remain upright and keep oriented
with respect to the vertical and our goal. Paying concentrated attention to
the relevant sensations is quite another matter, but we ind out which is the
downward direction and are constantly reminded of it from the downward
pull on our body and the efforts we need to make to resist falling to the
ground.
The Foundations of Perception
It might seem that at least some of what has now been said is overstated. If we
look at the psychological literature then it is clear that apart from a vestibular
judgment of the vertical our vision also provides a reference and the two can
even come into conlict. It is also well known that pilots should not ly ‘by
the seat of their pants’: if they lose visual reference by lying through clouds
they are liable to crash. Perhaps the vestibular apparatus or even balance is not
essential after all.
Two clues to what is important, both mentioned by Reid, are relevant.
We should not be considering abstractions such as extension and depth, or
just one direction or a horizon alone; we should relate our performance to
the Laws of Motion. As Reid understood these, this is Newtonian dynamics
in which vector forces are taken to be real and the composition of forces
determines how one should direct effort in moving and turning and so on.
23
J. W. O’Dea, ‘A Proprioceptive Account of the Sense Modalities’ in Macpherson (ed.),
The Senses: Classical and Contemporary Readings, 308, emphasis original.
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Also, we should consider how balance develops and how our directed actions
allow us to acquire habits of perception. That habits are as important in seeing
as they are in walking and moving was evident to Reid already in the Inquiry
where he speaks of how infants learn to see objects:
From the time that children begin to use their hands, nature directs them
to handle every thing over and over, to look at it while they handle it,
and to put it in various positions, and at various distances from the eye.24
He then continues to emphasize the importance of acquired perceptions and
perceptual habits. So in brief we don’t want vague talk of motion, nor the
abstracting out of spatial relations such as extension, or of duration. We want
to determine the precondition for actual purposive movement characteristic
of an agent. Whether this be a response to a speciic stimulus or the enacting
of an imagined scenario, this motion is a from-to movement accomplished by
an effort and not just a kind of passive drift or a senseless lailing about. The
fundamental starting point here is not knowledge of space as an abstract room
to move but knowledge of direction and acceleration.
It is essential to recognise that without direction and orientation we not
only cannot move as we will, we also cannot see objects since the precondition
for seeing something is to look at it and keep still or at least distinguish motion
of the object from the motion of the observer, as Wells pointed out. This is the
basis for identifying persistent individual objects rather than merely facing a
confused play of colour. The perceiver can eventually acquire habits of seeing
so that vision can compensate some acquired deiciencies of balance, but
vestibular functioning is the key ingredient for developing spatially informative
seeing, just as it is for goal directed movement. In linking balance closely to
voluntary motions Reid is effectively granting the agent an ineliminable role
in not just moving, but in perceiving. To be a bit provocative, perhaps one can
say that balance is a precondition for physical agency and perceptual learning.
If vestibular function has an important role in this then this set of organs
must be in place before the development of perceptual habits can begin and
vestibular information on the spatiotemporal structure and dynamic response
of the physical world is then integrated into all these habits. These habits
include what we ordinarily call seeing and hearing. These large claims can be
illustrated by some recent research into vestibular functioning.
24
Thomas Reid, An Inquiry into the Human Mind on the Principles of Common Sense
(Pennsylvania, 2000), 201.
Reid’s Discovery of the Sense of Balance
15
Firstly, all moving organisms which have something invested in going in a
particular direction have some organ for determining the downward direction.
These organs are some of the most ancient in evolutionary terms.25 For an
organism which is extended and has proprioceptive knowledge of bodily
position only one direction has to be ixed in relation to the environment
for the organism to ix its own frame of reference and measure or compare
positions and movements of objects. It is dificult to see how this might
develop without a universal direction and a means of ixing it.
Secondly, as a recent review of vestibular functioning puts it:
Unlike other senses, vestibular information in the central nervous
system becomes immediately multisensory and multimodal. There is no
overt, readily recognizable conscious sensation from these organs, yet
vestibular signals contribute to a surprising range of brain functions,
from the most automatic relexes to spatial perception and motor
coordination.26
Thirdly, as Daphne and Charles Maurer explain in their book on the
cognitive development of infants:
Of all the sensory systems, the vestibular system is the irst to mature.
The organs of balance in the inner ear are mature in shape and are
partially innervated before eight weeks of gestation. By six months
gestation they are not only mature in shape, they are also mature in size
and are completely innervated – the only organs in the body to become
adult during gestation.27
This, by the way, is the reason why newborns can already have spatial
competencies – they acquired them in the womb. Fourthly, in speciic
comments on the sensations experienced by newborns the Maurers note that:
Adults’ sensations rarely spill from one sensory system into another, as
the newborn’s do. But a signal exception to this lies with our sensations
of balance and sight, which work together so closely that if we close
25
26
27
S. McCredie, Balance, In Search of the Lost Sense (New York, 2007), ch. 4.
Angelaki and Cullen, ‘Vestibular System: The Many Facets of a Multimodal Sense’,
125.
D. Maurer and C. Maurer, The World of the Newborn (New York, 1988), 161.
David Vender
16
our eyes and pirouette, after opening them again, the world looks as if it
is moving. In contrast, the newborn’s sensations spill about throughout
his brain from one system to another, because his brain lacks the adult’s
deep network of neural channels; and one set of these channels that
is not mature is the set that links the vestibular and visual systems. So
the one place where adults are signally synesthetic, the newborn baby
is not.28
What the baby is learning in perceptual learning is to integrate vestibular and
bodily information with external stimulation by light and sound. So, far from
separating itself from the environment, it is placing its body and integrating
its sensory organs into the dynamic world. Fifthly and lastly, Patrick Wall has
something fascinating to tell about balance in his book on pain. In talking
about people who have suffered a stroke which has destroyed their inferior
parietal cortex, he tells us that:
If the stroke has occured on the right side of the brain, these people
appear completely unaware of anything on the left side of their world.
They appear blind and deaf to anything occurring on the left and,
most bizarre of all, when shown their own left hand they deny that
it is part of them. … Now comes the really astounding fact. Italian
doctors, whose results were conirmed by many others, discovered that
stimulation of the vestibular system in the ear completely restored all
sensation on the left side. It disappeared again as soon as the stimulation
stopped.29
There is no perception of spatial relations in the world without the enabling
role of the vestibular system in our sense of balance.
As already noted, neither Reid nor Wells were actually talking about the
vestibular system. Wells in his experiments comes closer to investigating the
rather direct link between eyesight and vestibular stimulation, but Reid was
really talking about actively maintained bodily balance. Now there is at least
one way in which it is right to say that we do not do anything with the vestibular
organs when we collect the information needed to balance. The actual organs
are beyond voluntary control. The same can be said of the olfactory receptors
and even the ears. When we sniff or cock our head to hear we are not really
28
29
Ibid., 164 – 5.
P. Wall, Pain: The Science of Suffering (New York, 2000), 148 – 9.
Reid’s Discovery of the Sense of Balance
17
moving the organ but merely orienting it or stimulating it indirectly.
This has important implications for placing the vestibular apparatus
correctly into the sense of balance. Vestibular signals are not enough if what
one wants to achieve is balance or if they wish to educate their eyes and ears
about spatial relations and relative motions. To do any of that we actually have
to use our muscles and exert effort. Fully functioning vestibular organs are not
even essential for balance and once we achieve the upright posture vestibular
information plays no part in maintaining it.30 It may then well be asked what
its main role is in the sense of balance and in perceiving.
The general answer is that the sense of balance involves vestibular,
proprioceptive and tactile systems. The extent to which all these systems
contribute and how malfunctions are compensated raises empirical rather than
philosophical questions. What makes the vestibular organs special is that they
provide that ‘secret reference’ directly to the head senses which we use to
see and hear with. These are our most important senses for the detection of
remote objects and the positioning of and control over the motions of the
head are needed to begin perceptual learning with these head senses.31
But given all this it is nevertheless wrong to call the vestibular system a
sense of balance for the simple reason that balance requires two participants.
The best that the vestibular sense can do is to provide some of the information
needed in this interaction, and the value of Reid’s insight lies precisely in his
placing the perceiver in the centre of the action of balancing.
Conclusion
Reid’s comments on balance still have the potential to change how we think
about our senses and how we draw the line between the active perceiver and
the physical world. His remarks occur in the context of a broad consideration
of voluntary motion and they allow us to see balance as a modality which
30
31
I. P. Howard and W. B. Templeton, Human Spatial Orientation (London, 1966), 255.
Even if the vestibular sense is not essential in maintaining the normal stance, it
becomes more important for keeping the head still and oriented while running. There
is good reason to believe that this has until recently had signiicant survival value, see
McCredie, Balance, In Search of the Lost Sense, 107 – 15. Large and sensitive vestibular
organs are a measure of agility and they facilitate skilled jumping and turning, not
to mention accurate throwing. On the other hand, impaired vestibular functioning
can be more easily compensated in humans than in other species, see Geldard, The
Human Senses, 426 – 7.
18
David Vender
involves the whole body in exploratory activity. Without this sense our agency
cannot come to expression in purposeful behaviour and the exploring needed
for perceptual learning cannot begin.
There is no perception of dynamical relations or spatial relations in the
world without our sense of balance. I would suggest that there is no perception
of the world at all.
University of Tasmania