Animal senses

Back at the end of last year, prompted by the Financial Times piece at reference 1, I bought the excellent book of popular science at reference 2. Being diverted down other paths, it has taken a while to read it, but I now have – and have found lots of thought provoking material about some curious senses packed into an accessible package. Mostly highly developed or specialised versions of sense that we have ourselves. Also having previously provoked the posts at references 3, 4 and 5.

A book of around 300 pages organised into twelve substantive chapters sandwiched between some introductory stuff and some closing stuff. Each chapter takes a curious animal as its starting point and are mostly in three interleaved parts: the animal with its interesting sense, a person who has lost the equivalent human sense and science soap. Tales from the daily lives of working scientists. Quite a lot of jumping between story lines, much as in a television soap. Which can also irritate after a while. 

A book which covers a great deal of ground, the sort of thing which can absorb a huge amount of fact checking. Probably best to do some of one’s own before putting too much weight on any one fact.

Unusually for these days, the book is made in England, rather than somewhere in the far east. Also unusually for a book of this sort, the decision was made to include no pictures, other than having a drawing of the relevant animal to introduce each chapter. I read somewhere that ‘Caroline Church is a scraperboard artist, and the perfect illustrator to approach if you’re after something with a vintage engraved look to it. Her imagery is ideal for packaging that has a traditional feel, she’s an expert when it comes to conveying atmosphere and fascinating results can be achieved when her historical scraperboard style is applied to modern themes and subjects…’. Scraperboard being new to me and catching my eye as something between the linocut and the woodcut. A sample is included above. So not a lady who specialises in animals, but she still does a pretty good job here.

So we as exemplar animals, the peacock mantis shrimp through to the duck-billed platypus – with a stuffed specimen of this last to be found in a corner of Beaney House of Art and Knowledge at Canterbury, for which see reference 6. But rather than attempt a quick canter through the twelve chapters, I shall start where I ended, with a primer on our senses generally, with the tabular summary ventured below.

At the level of receptors, animal nature is fairly conservative. Most animals make use of the same basic machinery, the same repertoire of receptors: the chemistry is much the same throughout the animal kingdom. So, for example, all animal eyes use the same chemical devices to convert light into electrical energy.

Then, the traditional identification of five senses – sight, hearing, smell, taste and touch – five senses which some Christians, with their well-developed sense of sin, map onto five kinds of sin – is not really enough, there is other stuff going on. So, for example, some animals – including at least some humans – can detect the earth’s magnetic field and use it to give them a sense of direction.

Then, leaving aside the question of sensing what is going on inside the body, there is the question of what sort of external stimuli we can sense, consciously or unconsciously. In evolutionary terms, chemical receptors might have been first, with each sort of receptor tuned to one sort of chemical. A lot more sorts than the modest number of receptors for different wavelengths of light, although trickery is possible and sometimes a receptor can be set off by some chemical other than that nature originally intended.

Some senses can do action at a distance, so human eyes can detect objects which are miles away and human ears can hear natural noises which are tens of metres away, and unnatural or unusual noises which are a good deal further away than that. Some senses, like touch, need contact and some, like sensing heat, that is to say thermal radiation, are in between.

Some senses, notably the eye, can detect the direction from which the stimulus came. In the case of humans this sense is so well developed as to enable the production of images in the brain.

Some senses only work when the level of background noise is very low. So the sense of direction which uses the earth’s magnetic field, is drowned out by the electrical clutter in a modern house. Detecting prey by their electrical emanations probably only works at the bottom of rivers, the bottom of seas where ambient electrical activity is very low.

All of which I found fascinating. And it was easy enough to chase up more information from the Internet when I want to dig a little deeper. No index, but notes and references keyed to each chapter. And the names of important players, important enough for search engines to bite on.

The book closed by emphasising the plasticity of the brain, the way that, for example, blind people tend to have better hearing and a better sense of touch that sighted people. This not being the result of better machinery out on the periphery, but the brain adapting to the loss of one sense by giving more resources to others. This allocation seemingly not being fixed by our genes, fixed from birth.

A few highlights

In Chapter I, after learning something about the peacock mantis shrimp, I learn that different people sense things in different ways at different times and places. Their sensors are perhaps tuned a little differently. The ambience might be a bit different – say different light or shade. Top down processing might be a bit different - say the tendency to see what we wish for or what we are used to, all of which might well vary from person to person. So I might see a black headed marsh warbler while you might see a crumpled fast food wrapper.

The suggestion from reference 7 snapped above being that maybe Van Gogh had slightly weak red reception, which means that he would turn up the red content of his paints, thus giving us what we see on the left, while what he saw was we see on the right, with the red content of the flower centres toned down a bit.

So we can have bottom up changes of a modest variety and rather grosser changes arising top down. But looking to the middle ground, whether we can reverse black and white, permute the primary colours or rotate the colour wheel, options floated at reference 3, is another matter.

Chapter V starts with vampire bats, which surprised zoologists with the amount of support offered by these bats to each other, family or not. A very cooperative lot. The chapter goes on to talk of the importance of something called slow touch, otherwise a stroke or a caress, enabled by things called C tactile afferents, afferents which seem capable of more or less directly eliciting pleasure or pain, sometimes in error, sometimes because of mutations in something called the SCN9A gene, otherwise the sodium voltage-gated channel alpha subunit 9. So a sense which is closely bound up with a pair of feelings. Some go as far to argue that these afferents are what drive, what enable, humans to be social animals, to get along in large groups. A lens through which to explain what it means to be human.

Chapter VI tells of a giant catfish which can taste with its facial whiskers and its skin as well as with its mouth. With the first two having one channel into the brain, and the third another, making it likely that there are different processing arrangements. Seemingly including the remote detection of the location of tasty prey. A wheeze which presumably only works for a water animal.

Chapter VIII tells us something of pheromones, chemicals which many animals use to guide or even direct their behaviour, particularly their reproductive behaviour. Chemicals which many animals can detect at very low concentrations and at some distance. Direction that need not trouble higher brain centres, given that the nose, unlike the other senses, has direct access to the lower brain. In can, in effect, just tell us to get on and do something, without troubling consciousness with the matter. There is some evidence that humans respond to such smells.

There is also some evidence, that the smell of a human comes close to being a genetic fingerprint, a unique identifier. Humans can, in consequence, tend to choose mates which are as genetically different from themselves as possible, thus bringing some new genes into the mix and largely avoiding children winding up with two copies of a bad recessive gene. All kinds of interesting possibilities. I associate to a comedy I once saw on television talking of the need for our aristocratic families to breed out every few generations, to pull in a few wild cards from the village, to avoid breeding problems.

While Chapter X tells something about spiders, their sense of time and our sense of time. With a lot of the material here being lifted fairly directly from reference 8. The idea seems to be that life is dominated by the cycle of the solar day, now, on average, very slightly less than 24 hours. So living organisms, particularly large and complicated animals which contain lots of molecular clocks to regulate, to manage, their affairs, set those clocks by the sun. Take the sun away altogether and the synchronisation of all those clocks starts to fail, with sometimes serious results. As can too much messing around with time zones. It turns out that this setting makes use of an additional photoreceptor on the surface of the retina, often still up and running even when the host is otherwise blind. With the result that these blind people are advised to spend time outside, in natural light, to help keep their clocks in order.

Lastly, somewhere along the line I came across reference 9, the opening substantive page of which is reproduced above. Hopefully I will do better than flip a few pages.

Conclusions

A good read. Strongly recommended.

For myself, nothing on how all the material collected up by the nervous system is organised for projection into consciousness, with my vote sticking, at least for now, with topical, that is to say with the material on a patch of cortex organised in much the same way as a picture on a piece of paper. But thinking about all the different kinds of material offered by the present book might give me a handle on some appropriate, general-purpose format. Maybe the layers of LWS-R of reference 10 are the answer. Maybe time for another look at reference 11.

PS 1: at one point I took a look at the puffs on the back of the book, all very gushing as one might expect. And not really in the same terms as I have been thinking about the book at all. First thought, this is all a lot of rubbish. Second thought, give some time to these other points of view. Maybe there is something in them!

PS 2: the grammar checker in Microsoft’s Word has been particularly irritating on this occasion. It is often useful, but I must learn how to turn it off.

References

Reference 1: What the platypus could tell us about climate change: The COP26 delegates would do well to look at the world from the perspective of animals – Jackie Higgins, Financial Times – 2021. 23rd October.

Reference 2: Sentient: What animals reveal about our senses – Jackie Higgins – 2021.

Reference 3: https://psmv5.blogspot.com/2021/12/on-seeing-colour-some-science-fiction.html. 

Reference 4: https://psmv5.blogspot.com/2021/12/two-sorts-of-fake-vision.html. 

Reference 5: https://psmv5.blogspot.com/2022/08/knowledge-without-sensation.html. 

Reference 6: https://psmv3.blogspot.com/2017/03/beaney.html. 

Reference 7: Art, interpersonal comparisons of color experience, and potential  tetrachromacy – Kimberly A. Jameson, Alissa D. Winkler, Keith Goldfarb – 2016.

Reference 8: The rhythms of life: what you body clock means to you! – Foster, Kreitzman – 2014. Being the Physiological Society’s annual public lecture for 2014. Short and accessible.

Reference 9: Animal eyes – Michael F. Land, Dan-Eric Nilsson – 2012. An open access book.

Reference 10: http://psmv4.blogspot.com/2020/09/an-updated-introduction-to-lws-r.html. 

Reference 11: The Merging of the Senses – B.E. Stein, M. Alex Meredith – 1993.