Review : Sentient (Part II)

Continuing a review/summary of Jackie Higgins Sentient. In part one I covered how biological senses are much more powerful than we might expect, even in us supposedly mediocre humans. In fact the basic sensory operations of many organisms appears comparable to the very best modern instrumentation. One photon of light, one atom of vibration, one molecule of a compound... the basic registration appears as good as can possibly be. The extraneous hardware - the shape of the nose, the ear, the size of the eye - that varies, but the fundamental conversion of the original signal into an electrical stimulus for the brain doesn't, or at least not much.

Animals do inhabit different sensory realities to ourselves though : that extraneous hardware makes a huge difference. A dog's nose being closer to the ground makes it far easier to access olfactory stimulation, and if its raw receiving power isn't that much greater than our own, its brain appears to be configured quite differently to deal with the signal. The great grey owl's face gives it far superior sound-collection powers, while the star-nosed mole's unique nasal protuberances allow for a sense of touch almost inconceivably different from our own.

Just how far does this go ? Here there is a slight weakness to Higgins book as she deliberately restricts herself to animal senses which humans are least partially share, so the electrical sense of sharks and the hydrodynamic sensing in fish don't get much of a look in. But as it turns out, there's some pretty compelling evidence that humans might share more animal senses than we usually assume. We think we all know about the basics of the eye and ear, but even these appear to have far more capabilities than our everyday experience. And as well as these familiar senses operating at a subconscious level, it also seems we might have other, wholly unfamiliar senses - without even realising it. 

In this second, concluding part, I'll look at some of those unconscious senses, beginning with the ordinary and progressing to the downright weird.

Sensing without sensation

Is it possible we have senses we're not aware of  ? To this the answer is a firm "yes". Blindsight is an intriguing one, but more ordinary examples include balance and proprioception (the sense of how our body is arranged - how we know where all our arms and legs are in the dark). Until these go wrong, we take them for granted. We don't have to think about which way is up, it is simply known. That knowledge is implicitly but not consciously filtered into our actions. 

It turns out there may be others as well. Some of these are more exotic than others, even verging on magical... which may go a long way to explaining why they've often been treated with extreme skepticism. Higgins notes many times when researchers, for a wide variety of reasons, have had great difficulty in persuading their peers that unconscious sensing is even possible.

Smell

Let's start with a return to the nose. In the previous section we looked at ordinary smells. More controversial are pheromones - scents which are "less chemical messenger than chemical command". In Dune, the Bene Gesserit use the Voice to cause override conscious objections : through the right tone of voice, tailored to the individual subject, Herbert posited that the conscious mind could be taken out of the loop, and so the Voice accesses direct, subconscious control. 

Pheromones, at least in animals, appear to be the nearest real-world equivalent. And they are incredibly potent. The giant peacock moth has more than three orders of magnitude fewer sensors than a dog's nose, but can detect female moth pheromones a thousand times fainter than anything a dog can pick up. How this equivalent millionfold increase in sensitivity is achieved is unknown.

I will take issue with a couple of claims in this chapter. First, that pheromones are such a more powerful command than other scents. That's as may be, but the giant peacock moth is not a good example - is it any wonder than an animal which lives only a few days, whose sole purpose is to reproduce, should react so strongly to a chemical stimulant advertising the availability of other sexy moths ? Higgins mentions pheromones in other animals, but never explains what the qualitative difference is. Second, that pheromones are perceived unconsciously - nowhere does she explain why researchers believe the effect is subconscious, why they don't think the animals perceive a smell they really like and react accordingly.

The point about pheromones overriding conscious control is not at all demonstrated for the case of humans either. And this is a problem, because such overstating the case has led to some ludicrous backlash. For example in one experiment trying to see if scent was a factor in human mate selection :

'Journalists got hold of the story and then politicians. One saw the words, "human, mate choice, genetics" in my proposal, tried to shut down the project and get me expelled. Then, she gave a nasty interview for an important local paper. Some of my volunteers read this and dropped out.' Other students started a protest. Newspapers quoted one who insisted the study was unsuitable because it 'optimised' offspring and another who claimed the study demeaned women by implying their 'functions and abilities are reduced to reproduction'. The furore grew. A politician denounced the project as 'Nazi research'...

All this for getting volunteers to smell some T-shirts ! But actually, nothing - nothing whatsoever - in the chapter implies that either gender is reduced to hapless sex-craved lunatics by a little sniff. It's about whether smell has an influence, not a matter of irresistible control. I cannot find anything in the chapter that justifies Higgin's description of pheromones are being qualitatively different in this regard from ordinary scents : sure, we all really like the smell of freshly-baked bread, but that doesn't send us spiralling into a whirlwind of self-destructive bread-based infatuation.

The point about smell causing an unconscious influence does seem on much more secure footing, however. Higgins cites the IgNobel*-winning study finding that strippers** received more tips when ovulating. In another case, heterosexual women and homosexual men were found to preferentially sit on a specially-dosed seat in a waiting room. Women rate men more attractive when they applied a certain compound, and when living in close proximity will synchronise their periods. Even babies react to the scent of their mother. And the T-shirt study which was eventually performed tuned out to have one of the most interesting results at all : mate selection seems influenced by complementary gene sets.

* The IgNobels are for research that first makes you laugh, then makes you think. They are not, despite the name and the often hilarious aspect, awarded because the research is bad or stupid.
** Sadly for the researchers they never had to interact with their subjects or even their environment.

In the main, these experiments are carefully done, repeated, and with multiple control conditions - Higgins is convincing in the claim that scent can have a subconscious influence. There's nothing here to me that says we're automatons with no free will, just that we don't act with 100% conscious control over 100% of our actions 100% of the time. From that perspective there's nothing new here. Far more interesting is that, like blindsight, our senses don't always interface directly with our mind. How does the brain decide what it is the mind needs to judge ? Why does it prefer to do some things consciously and some unconsciously ? And could we have other senses of which we're entirely unaware ?

Sound

Remember how the owl uses its entire face like a giant ear ? It seems that humans have more in common with this than you might think. Some blind people have trained themselves to make clicks and use the echoes to judge distances to nearby objects, but this is done through conscious training. Hearing also, however, provides subconscious information. Higgins recounts the tale of a man who went blind but began to develop a replacement faculty for his lost vision :

'In the quiet of an evening I had a sense of presence, which was the realisation of an obstacle. I discovered that if I stopped when I had this sense, and waved my white cane around, I would make contact with a tree trunk. I gradually realised I was developing some strange kind of perception. The experience is quite extraordinary, and I cannot compare it with anything else I have ever known. It is like a sense of physical pressure... upon the skin of the face.'

This so-called "facial vision" has been explored with controlled experiments, in which blind and sighted (but blindfolded) volunteers walked in a room until they thought they had reached the edge. While the blind people stop sooner, the sighted people also do not collide - unless, that is, they are also wearing headphones. In 400 such trials, not a single person failed to collide when deafened. And, when the headphones were not silent but connected to a microphone held by the volunteer, they regained their ability of collision-avoidance (which could be done to within an inch of the wall). It seems that hearing gives us much more information than we consciously realise, even if we don't have the capabilities of an owl or a bat - and there is real substance to the claim that blind people develop an improved sense of hearing.

Identity sentience

Before I get to the really whacky stuff, a few others deserve at least a brief mention. Rather than smell, the goliath catfish has adapted to have an extraordinary, full body sense of taste. More like our own sense of smell than taste, they can taste at a distance, in three dimensions, via taste buds distributed over their entire surface. Exactly how it experiences this is a mystery (though they appear to be able to sense pH levels), but in humans taste receptors are not just found on the tongue and lips : they're also found in the respiratory and digestive systems.

Unlike the taste cells in our tongue's papillae, the scattered taste cells never lead to any conscious bitter, salty, sweet or sour perceptions; they 'taste', but we do not. They work beneath our awareness... These bitter receptors do not create taste sensations, but prompt our body to eject airborne toxins or pathogens forcefully... 'No-one has defined what solitary chemosensory cells are in fish, let alone in humans. We don't know what these cells are doing. We don't even know what they mean.'

Might they help explain the sensation of an upset stomach, something not easily described by other sensory stimuli ?

I don't know. If taste senses are found throughout more of ourselves than is usually supposed, our sense of touch may be even more integral to our sense of identity. Higgins cites the rubber hand illusion as a demonstration, noting the complications of phantom limbs. The arguably related "senses" of pleasure and pain blur the lines further*, clearly related to direct sensory perception but not straightforward equivalents either. Like wavelength and colour, there is a connection, it's just very unclear what that connection is.

* This is in the chapter on the vampire bat, which is ill-constructed compared to the others. This is a shame, because there's a lot of interesting stuff here, like how they rely on food-sharing to survive and have heat sensors as well as echolocation. Unfortunately the chapter is too unfocused, never settling on a topic to drill down into the details, and lacking an overall structure to tie it all together.

Proprioception may be one of the strongest clues to a sense of identity. Here Higgins, I must say, does a better job of conveying what it's like to lose this sense than even the formidable Oliver Sacks. Both authors describe how patients learned to compensate with vision, able to send motor signals to their limbs but not receive the usual direct information about how they're positioned. Neither author is able to describe how this actually works usually - how exactly does the brain know about limb position ? Clearly we know this with a fine degree of precision; as I type this, my fingers flick back and forth over the keyboard without even needing to look at them. The brain does this with immense reliability and speed - how ?

Losing the sense is undeniably strange. Higgins describes a patient slowly (very slowly) learning to control himself as very much like the "wiggle your big toe" scene in Kill Bill 2. 

By staring at a limb, a digit, any joint, once again his brain was able to issue commands and move it. Vision and intention could stand in for his loss of proprioception. To this day, he remains utterly reliant on his eyes. If the light fails, he falls. If his focus falters for even the briefest of moments, he falls.

Higgins describes him as being both the puppeteer and the puppet. We are generally aware of "the aim, rather than the many acts required en route". Not so perhaps for the octopus, which might exist in a state not dissimilar from proprioceptionless-patients. Citing Peter Godfrey-Smith, it may generally leave its own limbs to get on with things independently most of the time, but the central brain has the ability to override and draw everything together when need be. 

Perhaps this isn't so different to the rest of us. As with blindsight, if your mind wanders, your limbs are fully capable of managing actions on their own... as Higgins says, you don't normally need to think about the minutiae*, but sometimes you don't even need to think about the aims. The number of times I've walked one door down the street from where I need to be, I couldn't tell you. It doesn't feel like I've lost my sense of identity though; we may all of us have a bit more in common with the octopus than we think.

* And when you do, what does this feel like ? Can you describe it ? I can't. It's some sort of irreducible knowledge, more than a mere sensation, that I'm in control of my actions : this is my will made manifest. 

Magnets

Okay, now we get into the more outlandish. We all know birds navigate in part by the Earth's magnetic field, but it seems some other animals can do this too. But how ? What does it feel like ? And if something as humble as a pigeon has this ability, why not people ?

Higgins describes at length the experiments to establish that birds do indeed navigate by the magnetic field, and moreover, this is disrupted by human electronics. Fortunately even going just outside a city is sufficient for these artificial fields to weaken so that birds can once again rely on their natural ability. Yet the sensitivity is, as with the other senses we saw last time, truly extreme : 

The bird compass can respond to forces that are one fifty thousandth [1 nanotesla] of the natural magnetic field... 'substantially below anything previously thought to be biophysically plausible. The bird's magnetic compass is a million times more sensitive than any other sensory system known.'

The debate over how exactly birds are able to register such changes is ongoing. There are two main theories, which is this case are not necessarily mutually exclusive. One is that it's from magnetite crystals found in the beak, a nice simple idea but potentially with problems explaining the extraordinarily high sensitivity levels. The other is a quantum theory which has no such difficulty, and potentially equips the birds with a whole new kind of vision :

Cryptochromes are found in the retinal rods and cones of a bird's eye. When a photon hits rhodopsin, its retinal molecule snaps into a different shape, setting in motion an act of sight; the quantum compass theory proposes that when a photon strikes a cryptochrome, it generates free radicals with mismatched pairs of electrons... their magnetic fields could interact with the Earth's magnetic field.

The objection from the magnetite camp is that this doesn't explain navigation in the dark, but we've seen that the eye can be sensitive to individual photons so this seems like a weak argument. Still, there's no reason birds might not use both systems. And, being in the eye, does the bird literally see the magnetic field, or perceive it in some other way ? Likewise, as to why it needs such extraordinarily high sensitivity levels, this is left unsaid. 

There's evidence that a host of other animals might use magnetic navigation as well : deer, turtles, eels, lobsters, snails, butterflies and mole rats. What about people ? We obviously can't "see" the magnetic fields in the way that birds (tentatively) might be able to, but could we be aware of it subconsciously ?

Evidence suggests... probably. Experiments taking blindfolded students on a long drive* found that they were remarkably accurate at pointing their way home, despite consciously stating that they have no idea where they were. But these had mixed results at best and replication was a problem, with even individual students giving highly variable results. Using EEG scanners with subjects in Faraday cages and sensory deprivation tanks* appears to be more promising, with changes in brain waves being induced in response to a magnetic field. More replication is needed, however, as is the need to find the sensor. But my impression is that the work which has been done so far is already so careful, so meticulous, that there is very likely something in it.

* And not murdering them at the end.
* The pro-magnetite crowd says this refutes the quantum vision theory, but it's not clear if these tanks really eliminate all photons, which is not such an easy task.

Most intriguingly of all, Higgins describes the case of the Guugu Yimithir aboriginal people of Australia, who demonstrate an ability similar but much superior to the blindfolded students. Another Australian tribe even lacks words for left and right, instead describing all directions in compass-style terms :

"They cannot explain how they know the cardinal directions, just as you cannot explain how you know where in front of you is and where left and right are. They simply feel where north, south, east and west are."

We've come across such abilities and people before. It's been suggested that is the language itself which bestows this magical ability, somehow granting us access to a whole other cognitive realm. This I have never found convincing. More plausibly, language is more a description of our (most fundamental) worldview rather than influencing the very basis of our perception. But that hasn't been a satisfactory explanation for how people could think in terms of absolute orientation - until now. I would not hitherto have speculated that humans could have an unsuspected magnetic sense.

I noted last time that this cardinal description of direction fades when people are sent from the flat terrain, where it usually develops, into somewhere more varied, but this is not at all mutually exclusive with the prospect that humans do also posses a magnetic sense. It might be dominant in flat, featureless deserts, and subsumed in more complex regions where landmarks are just a superior, easier method of navigation. Hence the language evolved in response to the particular circumstances : in this environment, humans are naturally far more in tune with this particular sense; it is the sense that causes the language, not the other way around. The only radical aspect would be the magnetic sense itself, with Higgins noting researchers face an uphill battle against the bias surrounding unconscious senses.

Time

Last but not least, how do we sense time itself ? Of all of physics, time seems one of the most mysterious of everyday realities. Some claim it's just an illusion created entirely by conscious perception, that it has no physical meaning in the way that space and mass do, while others hold that the forward progression of time is central to scientific understanding. Regardless, we clearly have an internal way of measuring time, however imperfect, so how does our internal clock actually work ?

The most obvious daily marker of time is the Sun, so experiments have revolved around depriving human and animal subjects of daylight. And indeed, orbweaver spiders show a natural rhythm independent of daylight - but it's not 24 hours, or even a multiple of 24. It can be anywhere from 18 to 28 hours, meaning that they live the life of the permanently jet-lagged. Why it isn't 24 hours, or at least something close to 24, is a mystery. But neat rhythms they naturally keep, regardless of sunshine, as do at least some plants.

As do also humans. Our body clock is set to 24-25 hours, which is a lot less weird (and makes a mockery of claims that humans could never adapt to the Martian 24.5 hour day). Yet, even when we can't see the Sun, it seems we can see time. 

Or rather more accurately : whatever process we use to sense the passage of time is present in our eyes. The Sun acts, if you like, to continuously set the hour hand, but the more frequent ticking is set by something in our eyes - provided we have incoming photons, whether from the Sun or no.

Experimental evidence of this comes from an unpleasant source. Postulating that vision had something to do with it, researchers engineered a mouse which had neither rods nor cones in its eyes. It was indeed blind. But it maintained a regular sleeping rhythm... until it was blindfolded. There is a third photoreceptor within the eyes, which has now been found and given the atrociously poor name of the "photosensitive retinal ganglion cell". Particular kinds of blindness in people have also been found to cause "time blindness".

How this actually works is a mystery. Could organisms be genetically encoded with some knowledge of the speed of light, such that something like a light clock could be present somewhere ? Nobody knows, though it would make sense that photons could be used for this just as they can be used for sensing magnetic fields. Nor, as far as I know, has anyone tried measuring the effects of complete, zero-photon darkness for protracted periods (elsewhere Higgins describes how this leads to hallucinations, so such extreme sensory deprivation might be fraught with ethical considerations). Certainly we don't literally "see" time. But that such a well-studied organ as the eye has such radical surprises in store for us only underscores the importance of further research, and how the nature of sentience itself is still an open question. Just what other senses might we have ?

Conclusions

Some of the bias against unconscious senses is understandable. The prospect that we could use photons to sense time and magnetic fields has more than a faint whiff of ESP and the like about it - if we can sense a global field which propagates at the speed of light, and given that birds have an apparently unnecessarily high degree of sensitivity, it's hard not to wonder if maybe this couldn't be used somehow for communication.

But this is unnecessary, and not warranted from the data. What's most compelling to me is that the mechanism for sensing the magnetic field relies on perfectly ordinary physics, and doesn't require the sensing process to be anything other than strictly one-way. That's not anything that even the most ardent skeptic should be worried about. Likewise, some of the bias against smell in particular is bizarre; to suppose that we are creatures of pure conscious choice is about as daft an idea as I've ever heard. No, because you subconsciously like the way someone smells does not make you a Nazi, you daft cultural warmonger. And I need to emphasise again just how careful and painstaking this research has all been, often a case of two steps forward one step back and then three more steps twirling sideways and falling over - establishing the magnetic sense in birds took seven years and more. The results are hard-won, rigorous science.

Still the question remains as to why these senses are subconscious. Especially interesting is that this occurs routinely in senses we also perceive consciously, like hearing (and on occasion vision). Why does the brain decide we don't need this information ? Why can't I get access to this normally, and just what else might the brain be doing in the background that it won't tell me ? That seems to open the door to those other, more radical sensory prospects.

As for language, as I've said many times, it is surely an interplay between deeper thought and expression. Even highly abstract, complex processes (like solving a differential equation) are done at some much deeper level within the brain, without the brain literally doing mathematics in the pen-and-paper symbolic sense. Yet when something is written down, that can trigger thoughts in new directions - the imperfection of language for recording and storing what we really mean is often a strength. So I think we can put safely to bed any notions that you need a language to really fundamentally alter our concepts of space and time, or give us new senses. It's still fascinating that we can use this to go in the other direction - to seek out cultures where, perhaps, our other hidden senses have risen to the top, shaping the way they express themselves.

Is one perception more valid than another ? This is hard to answer. Clearly some are more useful than others, but whether one is more "right" than another is altogether more challenging. Personally, I would welcome more sensory input. When the cyborg revolution begins in earnest, hook me up - let me hear those X-rays and smell the dark matter. I have no idea what this would be like, which is exactly why I'd want to do it.