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\title {Central Themes in Philosophy \\ Lecture 02}

Lecture 02:

Central Themes

\def \ititle {Lecture 02}
\def \isubtitle {Central Themes}
\textbf{\ititle}: \isubtitle
\iemail %
Here is are some flowers. You and I see these flowers and are thereby aware of them. For you and me, seeing the flowers involves more than simply acquiring visual information from them. For seeing the flowers is a way in which we can be conscious of them.
Bees have some visual abilities and they can discriminate some colours as well \citep{Kelber:2003hb}. So a bee could acquire some of the same visual information that you and I can from a sensory encounter with these flowers. In a basic sense, the bee sees the flowers just as you and I do. But is the bee conscious of the flowers? Would a bee who saw the flowers thereby be conscious of it?
It’s hard to know how you would even begin to answer this question. We now know quite a lot about the behavioural, physiological and neural aspects of bee vision (ibid.). But none of this seems to bear in any clear way on whether in seeing things bees are being conscious of them.
The point I want to emphasise is not just that there is little consensus on whether bees are perceptually conscious of objects. This is true but there’s a deeper point. There’s little consensus even on the issue of how we might go about investigating this question. This is a sign that we do not understand what consciousness is.
Consciousness is unlike many other central features of our lives in this respect. Other central features of human life, such as disease, reproduction, cooperation, language and politics can be investigated. In each case there are basic facts that most researchers accept and broad agreement about methods of investigation. None of this holds in the case of consciousness.
Don’t let my use of the bee give you the wrong impression. The key issue isn’t whether the bee is conscious or not. That might be important for the bee but it isn’t very important for understanding consciousness. The key problem is not really to work out which things are conscious and which things are not. The key problem is to understand what consciousness is well enough that we can investigate it in some of the ways that we investigate other phenomena.
I’m just using the bee to highlight our ignorance. The truth is that we don’t understand what consciousness is well enough to study it.
If we are ever to understand what it is, we need to start thinking about what roles consciousness plays. Why does it matter that we are sometimes conscious?

What are the functions of perceptual awareness?

There are different forms of consciousness. For example we sometimes contrast being conscious with being comatose. That’s not the sort of consciousness I’m concerned with. Instead I want to focus on perceptual consciousness of objects. When I talk about consciousness, I mean the sort of consciousness that is often involved when you see an apple’s shape and location. This is perceptual consciousness of objects.

What are the functions of feathers?

heat regulation



Ok, now shelve the question about the function of perceptual awareness. For now I hope you get that the question is nontrivial. I want to suggest an indirect way of answering it via the topic of perception without awareness.

A Secondary Subwaking Self?

\section{A Secondary Subwaking Self?}
\section{A Secondary Subwaking Self?}

What are the functions of perceptual awareness?

Simple Hypothesis

Perceptual awareness enables us to identify and report the letter.

k  k  k  k

Identify this letter ...
Against the Simple Hypothesis, consider an older experiment, first reported in 1898 by Boris Sidis. Sidis showed subjects cards containing a single printed digit or letter ...
“The subject was placed at such a distance from the card that the character was far out of his range of vision. He saw but a dim, blurred spot or dot” (1898: 170).
In fact, “subjects often complained that they could not see anything at all; that even the black, blurred, dim spot often disappeared from their field of vision” (1898: 171). Some people said “that they might as well shut their eyes and guess” (1898: 171).
However, when Sidis asked his subjects to name the characters on the cards, their responses were correct more often than would be expected if they were just guessing. This is surprising, because it’s natural to assume that what you consciously see determines what you write down; the Sidis’ results show that this isn’t always true.

‘the presence within us of a secondary subwaking self that perceives things which the primary waking self is unable to get at’


Sidis, 1898 p. 171

Apparently, Sidis interpreted these and related experiments as revealing “the presence within us of a secondary subwaking self that perceives things which the primary waking self is unable to get at” (1898: 171). In other words, it isn’t you who is responsible for writing down the letters at all: it is another person who shares your body and sees things you don’t.
Postulating a secondary self seems to make these results more, not less, confusing.
Not many people would accept Sidis’ suggestion, but it does show how radically the discovery of nonconscious causes of action undermines a very intuitive idea about how consciousness and action are related. Ordinarily we think that we act on what we consciously see. This is bound up with the sense we have of being in control of what we do, and of knowing what we are doing. If some actions are based on information we don’t even know we have, there is a sense in which these actions are not our own. So you can see why Sidis thought he had discovered a second person within his own body.
Natural thought is that there are many perceptual processes which do not involve awareness at all ...


Sidis’ subjects are not perceptually aware of the letter but can identify and report it.

So we are left with the question ...


exercise (will be useful later): point at the dot
exercise (will be useful later): point at the dot

What are the functions of perceptual awareness?

Simplest Idea:

Perceptual awareness enables control of action.

Ex. You can point at the dot because you are visually aware of it.

Blindsight is ‘the ability

of patients with absolute, clinically established, visual field defects

caused by occipital cortical damage

to detect, localize, and discriminate visual stimuli

despite being phenomenally visually unaware of them’


Cowey, 2010 p. 3

Blindsighted people have a region of their visual field in which they have no conscious visual experience: to them it is as if they are blind. When objects are presented to the affected area of their visual fields, they say that they cannot see them. However, blindsighted people are able to act on the basis of visual cues presented in this part of their visual field. For example, here is a diagram of the complete visual field of a blindsighted person.
The grey area represents the region affected by blindsight. This person can only consciously see the word ‘bank’. However, if we ask her to define ‘bank’, she is very likely to think of bank as a financial institution rather than as the kind of thing you find by a river:
this tendency is reversed if we put the word ‘river’ in her blind field. Although she cannot consciously see the word ‘money’, she does somehow discern the difference between this word and the word ‘river’.
Blindsighted people can also act on the basis of their blindsight, even though they do not consciously see anything. For example, if you flash a point of light somewhere in the affected part of their visual field, they see nothing. But if you ask them to point at the light by guessing where it is, they can point with surprising accuracy. With practice, blindsighted people can also reach for and pick up objects of different shapes and sizes. In fact, someone with blindsight can perform many non-reflexive actions guided by various kinds of visual stimuli in her region of apparent blindness. Blindsighted people can discern pattern, orientation, light wavelength, and the direction of moving objects. This is surprising because the blindsighted person does not consciously see the things she can point to or reach for. To her, the pointing and reaching seems just like guessing.
So blindsight enables people to discriminate visual stimuli. But consciousness is missing. To enjoy blindsight of objects is now a way of being conscious of those objects.
How is blindsight possible? From a purely neurological point of view, there is no mystery. Blindsight is caused by damage to the striate cortex (also known as V1), an area at the back of the brain. The striate cortex contains a kind of map of the visual field, and damage to part of the striate cortex causes blindsight in the corresponding part of the visual field. Although the striate cortex is the largest and most important region of the brain for visual processing, it isn’t the only target for optic nerves. Other parts of the visual system remain intact, so it is to be expected that damage to the striate cortex should leave some visual functioning intact. The brain damage that causes blindsight is completely different from damage to the retina or to the optic nerves.
For this reason, the original puzzle about blindsight wasn’t that people with damage to the striate cortex could act on the basis of visual information; it was that damage to their striate cortices should have such a dramatic effect on their vision. Research into the striate cortex was first done on monkeys and dogs. Early experimenters looked at what happens when you remove this part of the brain. At first they thought the striate cortex was not involved in vision at all, because when you remove this part of the brain animals recover the ability to make fine visual distinctions. But around 1884, Luigi Luciani noticed that animals without a striate cortex suffer from what he called “psychic blindness”. He observed that: although “visual sensation becomes perfect again [and] they are able to see minute objects, what they want is the discernment of things and a right judgement concerning their properties and their nature; they are deficient, in a word, of visual perception. For example, if small pieces of fig, mixed with pieces of sugar, are offered to them, they are incapable of choosing by sight alone but require to take the sugar in their hand and put it in their mouth in order to reassure themselves.” (Luciani 1884: 18) More recent experiments with monkeys have found the same thing: “After six years [one monkey] still does not know a carrot when she sees one, nor apparently can she recognise my face, despite an excellent ability to locate visual events in her environment and to avoid obstacles by vision alone” (Humphrey 1972: 684).
It was therefore puzzling that humans with damage to the striate cortex appeared to be completely blind in the affected regions of their visual fields (Weiskrantz 1986: §1). Psychologists searched for residual visual capacities in people with damaged striate cortex, and this led to the discovery of the phenomenon called blindsight. They expected to find some visual abilities, but they were surprised by what they found.
So there’s no mystery about blindsight from a purely neurological point of view. But blindsight is mysterious from the point of view of the person affected. As far as she is concerned, she doesn’t see anything. It comes as quite a surprise to her that she can point at and reach for things she can’t see: it must be a bit like discovering you’ve always had eyes in the back of your head.
Same idea but with more pathways and visual areas This is with V1 intact (V1 is top right)

Cowey, 2010 figure 2

This is with V1 taken out

Show me some evidence!

Ok, let’s look at some data

Weiskrantz et al, figure 2

Ok, let’s look at some data

Weiskrantz et al, figure 2

Important thing here isn’t that we know the patient (G.Y.) is unaware; in fact G.Y. reports awareness in many cases. The key is that whether G.Y. reports awareness appears to be statistically unrelated to G.Y.’s discrimination performance.
Two measures: 2AFC for orientation (vertical or horizontal). And yes/no for awareness
G.Y. ‘was insistently instructed, and frequently reminded, that he was to signal unaware only when he had absolutely no sensation or feeling or experience of the visual event, and he repeatedly confirmed his conformance With this instruction’ \citep[p.~6122]{weiskrantz:1995_parameters}.
caption: ‘FIG. 2. Discrimination of horizontal vs. vertical movement (FR paradigm), as a function of stimulus contrast. The subject had to indicate (by guessing if necessary) whether the presented stimulus was moving horizontally or vertically by pressing the appropriate response key. He also had two commentary keys to use on every trial. Awareness refers to the percentage of trials on which the subject pressed the aware key. Correct when unaware refers to performance during those trials when the subject pressed the unaware key. The luminance of the test stimulus was held constant at 131 cd/m2, and background luminance in the blind hemifield was altered systematically thus changing the contrast of the stimulus. Speed was 150/s, and displacement was 200. Note the relative stability of the high level of performance indepen- dent of contrast but with a steep decline in percentage of aware responses at high background luminance level when the contrast decreased’ \citep[p.~6123]{weiskrantz:1995_parameters}
\citet{weiskrantz:1995_parameters} show that a blindsighted patient’s visual discimination capacities are unaffected by whether the patient is aware of stimuli.

Awareness makes no measurable difference to action.

recall earlier when I asked you to point at the dot ...

What are the functions of perceptual awareness?

Simplest Idea:

Perceptual awareness enables control of action.

Ex. You can point at the dot because you are visually aware of it.

Objection : Blindsight reveals that sometimes variations in perceptual awareness of the dot make no measurable difference to action.

At this point I was going to do blindsight in normal subjects \citep{Kolb:1995vs}. But there is a convicing failed replication of \citep{Kolb:1995vs}: \citep{robichaud:2003_inducing}!!!

‘there is no clear case of a task for which consciousness is required’

[...] ‘It is misguided to think that the function of consciousness must consist in tasks that can only be performed with conscious representations’ \citep{shea:2016_dualprocess}.

Shea & Frith, 2016


In conclusion, ...

What are the functions of perceptual awareness?

Simplest Idea:

Perceptual awareness enables control of action.

Objection 1 : Sidis’ subjects are not perceptually aware of the letter but can identify and report it.

Objection 2 : Blindsight reveals that sometimes variations in perceptual awareness of the dot make no measurable difference to action.

Objection 3 : ‘there is no clear case of a task for which consciousness is required’ (Shea & Frith, 2016)