Nicholas Humphrey

Nicholas Humphrey recently produced a postscript to his book “Seeing Red”. He remarks with mild regret that some readers perhaps will still not “get it”: but if his theory is true, that’s only to be expected. If he’s right, the mysterious nature of qualia is really the point; if they were easy to understand, they wouldn’t do their job properly – a tantalising suggestion.

Actually I suspect that the most troublesome point in Humphrey’s theory, the one which most people tend to baulk at and the bit that’s hardest to “get” is his view of sensation, which he distinguishes from mere perception (the former involves having a subjective experience, the latter is just a matter of affectless acquisition of facts). The problem is that Humphrey insists that sensation “has something of the character of a bodily action”: it isn’t just passive reception. When we see red, the sensation arises from us “redding”, or to take a slightly more persuasive example, when we feel a pain, it’s because we’re hurting.

I must say that in the case of vision this seems completely counter-intuitive. Seeing colour feels very much like passive reception to me, but Humphries is very clear about its active character, referring to it as an example of agency. Agency surely requires control, the ability to act or refrain from acting; yet colour vision does not appear to be voluntary, like other examples of agency – I can’t switch to monochrome vision in the same way I can decide to shut my eyes. It would be a shame if this put people off the rest of the theory, however, because it seems to me that the argument works just as well if we take “redding” to be a purely reactive affair, devoid of real agency.

What is “redding” and other similar actions, anyway? Although Humphrey doesn’t describe it this way, we could regard it as a kind of second-order perception: a special sort of response to our own immediate reaction to stimuli. Once upon a time, our primitive single-celled ancestors might have responded to red light with a particular twitch of the membrane: as their descendants became more complex, Humphrey suggests, the initial reaction might have been disconnected from the twitch and used instead as the input to slightly more developed decision-making processes. Using your own reaction to stimuli as a source of information about the world has its limits, however, and ultimately our somewhat nearer ancestors would develop proper sensory apparatus separately. They would then have two channels providing information about the world: one a straightforward channel of perception, the other an indirect source based on monitoring the descendant of the old twitch-for-red reaction, still firing away somewhere in our brain. It’s this internal monitoring of the phantom twitch which provides the qualia; but in fact it does more than that.

Humphrey points out that although strictly speaking the present moment is an instant of zero duration, we do not experience it that way. Our experience is of a short stretch of time, with recent events still to some degree in our thoughts. He refers to this as the “thick present”, and suggests that a likely mechanism is a feedback circuit which causes present impressions to go on reverberating in our minds for a short time until they die away. It’s a plausible idea, though I suspect it may be a bit more complex than that: memory must surely be involved, and I would imagine that the level of attention we devote to things strongly affects the extent of their persistence and perhaps even the length of the perceived “thick present”. Be that as it may, the real point is that Humphrey thinks his “redding” mechanism provides just the right kind of feedback loop to cause the kind of reverberations he is proposing.

So far so good, but why should monitoring our own vestigial twitches be anything like subjective experience? Why isn’t it just like monitoring our own vestigial twitches? The fail-safe objection to any theory of qualia is the one that goes “Yes, but I can imagine all that stuff you describe happening in my brain or wherever, and me still not having any qualia”. For once, though, there is at least a tentative answer.

Humphrey arrives at this answer by asking himself a different question. Why have we retained this complicated feedback mechanism, he asks. Evolution tends to weed out redundant devices, so there must be a strong presumption that a qualia-generating facility has some very definite survival value. Perhaps we can spot what this is by considering the case of blindsight, the strange phenomenon of people who can’t see consciously, but can still point accurately to dots on a screen, or pick up objects without fumbling. Humphrey has a long acquaintance with blindsight: in fact he described a case in an experimental monkey before the human version had been documented. He tells the poignant story of a woman whose sight defect was corrected late in life. Because her brain had had no visual inputs it had not developed the processing arangements needed to deal with them, so although her eyes now worked perfectly she remained functionally blind. Or so it seemed: Humphrey suspected, and then confirmed by experiment, that although she had no conscious experience of vision, she did have a kind of general blindsight which, if she chose to use it, allowed her to perform all kinds of practical tasks which blindness had previously rendered impossible.

The strange thing is, she seemed unimpressed and unengaged by this new ability: did not enjoy using it, and eventually chose to give up on it and revert to being the blind person which, in her subjective experience, she had always been. Why? Qualia, Humphrey suggests, are profoundly engaging: they make things seem to matter. Without them, his subject was unable to get herself to take any real interest in her blindsighted abilities; and without them we should all have an anaemic grey existence composed only of dull information. It seems to follow that philosophical zombies, people just like us but without qualia, would turn out to have a zombie-like lack of interest in life too, and hence be indifferent competitors in the battle for survival.

But why do qualia make things seem to matter? Because, in the final analysis, they are part of us; whereas our objective senses tell us about the external world, qualia are really our own internal reactions: surely it is only logical that we should find them more vivid and more important than simple facts about the world. In fact, they are also the basis of our sense of self, and help explain our devotion to the survival of that self, too.

We can now see why Humphrey half-expects people not to “get it”. If it were clear to us that qualia were merely mental reactions, their valuable motivational effect would be dissipated, as would the useful delusion that we have a remarkable, immaterial self. It is only to be expected that evolution will have made the truth difficult to grasp, in our own interests.

This is a clever, cogent and rather ingenious argument, but I think I can see some rational reasons to doubt its truth. While perceiving qualia as part of ourselves might logically make them more important to us, I’m not sure that the idea of an immaterial self naturally encourages us to take a keen interest in the survival of our bodies. In fact, we know quite well that the opposite is the case: people who believe strongly in the immortality of the soul are less concerned about death, and may even seek out martyrdom.

More generally, does the wonderfulness of qualia really motivate us to be better survivors? It seems as likely to have us wasting time marvelling at the beauty of the daffodils while a tiger creeps up from behind: in survival terms it seems hard to beat the value of those grey but accurate facts. Actually, it is usually taken to be an essential property of qualia that they have no effect on our behaviour – if you’re talking about something that changes the decisions we make, on this view, you’re not talking about qualia at all.

I certainly have some reservations, in any case, about drawing many conclusions from blindsight examples. It seems quite likely to me that paying continuous attention to the subliminal or unconscious influences through which blindsight presumably works might be an exhausting, difficult, and uncertain business, one which the unfortunate woman in the case Humphrey quotes might easily have found burdensome, rather than simply unengaging through its lack of qualia.

There’s something a little fishy, too, about the argument that qualia have a special impact because they are part of us. I can only care particularly in this way about things I know to be part of me – yet my redding has its special effect just because I don’t recognise that it is internal (in fact, I imagine it to be a feature of red objects out there).
So although Humphrey’s argument is a clever, interesting, and indeed quite persuasive one, I’m not quite convinced. Perhaps it’s true that in one way or another evolution has destined me for disbelief in this case.

(More here, about Humphrey’s 2011 book Soul Dust. And a better picture – I think my drawing skills have come on a bit.)


  1. 1. Conscious Entities » The Genuine Problem says:

    […] Do the three go together? I suppose the insight that links them all is that knowing how something feels to us helps us understand how similar experiences feel to other people (only helps, though – I think our understanding of other people consists of a good deal more than just empathy). It is certainly plausible that our understanding of our own mental states arises from our understanding of other people’s (though there are those who would say that it is our understanding of other people’s minds that leads us to think we have our own). Less persuasive on the face of it is the view that our subjective experience is a matter of knowledge about our own inner states. My subjective experiences appear to me to be about the external world for the most part, and it isn’t immediately clear why second-order knowledge of my own mental states should endow them with subjective qualities. Of course, some people have put forward theories very much along those lines – Nicholas Humphrey, for example. But you certainly can’t, as it were, have that conclusion for nothing. […]

  2. 2. Paul says:

    Can someone tell me if the statement above–Evolution tends to weed out redundant devices–means that over time through either natural selection or genetic drift–anatomical elements that do the same things tend to disappear? The word device is not clear to me, nor redundant.

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