Memory, p.31
Memory, page 31
In the process of learning to recognize its parents, the gosling’s IRM [innate releasing mechanism], which releases all filial responses, becomes associated with one of the most complex functions of gestalt perception. In ourselves, the analogous faculty of visually recognizing our fellow humans as individuals is largely dependent upon our perception of the configurations of eyes, eyebrows, and nose. It is surprising how effectively the covering of this area impedes recognition; the small, conventional carnival mask is sufficient to do so quite effectively. Curiously enough, it is the same portion of the head which is essential for personal recognition among geese; a sleeping goose with bill and forehead tucked under its wing becomes completely unrecognizable to its fellows and is occasionally bitten by mistake. One of the funniest sequences is that in which a gander, having thus bitten his beloved mate, recoils with astonishment and switches to abject greeting patterns. Fledged, full-grown goslings, temporarily separated from their parents, search for them most assiduously and, while doing so, respond optimistically to any goose that is not positively identifiable because its head is hidden under its wing or under water – as if it could be one of the lost parents, they rush up to it greeting intensely, and start back disappointed when the head of a stranger appears. Hand-reared goslings are perfectly capable of transferring their mechanism of facial recognition to the human foster parents in spite of the enormous differences of body proportions. After a time, and somewhat longer than that taken for parent-reared goslings to learn individual recognition, the filial responses of hand-reared goslings, such as greeting, following and snuggling up, can be released exclusively by the foster mother, no matter how she is dressed. It is the image of the face alone that is relevant, as the following response is in no way diminished if the body of the human, unlike that of a goose, becomes invisible when swimming.
From SEMIR ZEKI, ‘Art and the Brain’ (1988)
We know a little, but not much, about the brain’s stored visual memory system for objects. We know that it must involve a region of the brain known as the inferior convolution of the temporal lobes, because damage here causes severe problems in object recognition. Although very much in their infancy, recent physiological studies have started to give us some insights into the more detailed physiological mechanisms involved. When a monkey, an animal that is close to man, is exposed to different views of objects that it has never encountered before (objects generated on a television screen), recording from single cells in its inferior temporal cortex can show how they respond when these same objects are subsequently shown on the screen again. Most cells respond to one view only, and their response declines as the object is rotated in such a way as to present increasingly less-familiar views. A minority of cells respond to only two views, but only a very small proportion, amounting to less than 1 per cent, respond in a view-invariant manner. Whether they respond to one or more views, the actual size of the stimuli or the precise position in the field of view in which they appear make little difference to the responses of the cell. On the other hand, no cells have ever been found that are responsive to views with which the animal has not been familiarised; hence, exposure to the stimulus is necessary, from which it follows that the cells may be plastic enough to be ‘tuned’ to one or more views of an object. In summary, many cells, each one responsive to one view only, may be involved during recognition of an object, with the whole group acting as an ensemble. But the presence of that small 1 per cent of cells that respond in a view-invariant manner suggests also that form constancy may be the function of a specialised groups of cells, since 1 per cent represents an enormous number in absolute terms.
When undertaking their work, artists generally are concerned not with philosophical views but rather with achieving desired effects on canvas – by experimenting, by ‘sacrificing a thousand apparent truths’ and distilling the essence of their visual experience. We are told, for example, that Cézanne’s work is ‘a painted epistemology’ (Erkenntnis Kritik), since Cézanne supposedly shared Kant’s ideology. But Cézanne, in particular, put paid to all these empty speculations even before they were made when he said that ‘les causeries sur l’art sont presque inutiles’. I agree with Kahnweiler when he states, ‘J’insiste, en passant, sur le fait qu’aucun de ces peintres … n’avait de culture philosophique, et que les rapprochments possibles – avec Locke et Kant surtout – d’une telle attitude leur étaient inconnus, leur classement étant, d’ailleurs, instinctif plus que raisonné.’ The preoccupation of artists has instead been less exalted and more similar to the physiological experiments described earlier: exposing themselves to as many views of their subject as possible and thus obtaining a brain record from which they can distil on canvas the best combination. If, in executing his work, the artist is indifferent to these polar views – Plato on the one hand, and Hegel and Kant on the other – so should the neurobiologist be, if he accepts my equation of the Platonic Ideal and the Hegelian Concept with the brain’s stored record of what it has seen. Whether art succeeds in presenting the real truth, the essentials, or whether it is the only means of getting to that truth in the face of constantly changing and ephemeral sense data, the opposing views are at least united in suggesting that there is (Hegel) or that there should be (Plato and Schopenhauer) a strong relationship between painting and the search for essentials.
Daedalus, Spring 1988
From NICOLAAS TINBERGEN, The Study of Instinct (1989)
‘Localised learning.’ The student of innate behaviour, accustomed to studying a number of different species and the entire behaviour pattern, is repeatedly confronted with the fact that an animal may learn some things much more readily than others. That is to say, some parts of the pattern, some reactions, may be changed by learning while others seem to be so rigidly fixed that no learning is possible. In other words, there seem to be more or less strictly localised ‘dispositions to learn’. Different species are predisposed to learn different parts of the pattern. So far as we know, these differences between species have adaptive significance.
Some instances may illustrate this important fact of localised dispositions.
Herring gulls have a number of innate reactions to the young: they brood them, feed them, and rescue them if attacked by strangers or predators. Interchanging the young of two nests of the same age has very different effects, depending on the age of the young. When they are only a few days old they will be accepted by their ‘foster parents’. But if the same test is made when the young are more than 5 days old, they will not be accepted. This means that after a period of about 5 days, during which a parent herring gull is willing to take care of any young of the right age, the parents are conditioned to their own young. They will then neglect or even kill any other young forced upon them. Approximately the same results have been obtained in various species of terns. This learning to ‘know’ the chicks individually is very remarkable, for the human observer rarely succeeds in distinguishing the young and never reaches the same degree of accuracy as the birds.
The ability of a herring gull to learn its own eggs is, by contrast, amazingly poor. The eggs of different gulls vary a good deal in colour and speckling, in fact they vary much more than the chicks do. Yet even gulls that have eggs of a very distinctive type such as bluish, poorly pigmented eggs, or eggs with exceptionally large or small spots, never show any preference for their own eggs. The innate releasing mechanism of the brooding reactions does not undergo any change by conditioning, so far as the egg itself is concerned. There is, in this respect, a sharp contrast between the reactions to young and those to eggs.
The sexual pattern, again, is readily conditioned. Herring gulls, like a great many other birds, are strictly monogamous, and each bird confines its sexual activities to its own mate once the formation of pairs has taken place. Here again the gull’s ability to recognise its mate is far superior to our powers of recognising the gulls. There is proof of the amazing fact that a herring gull instantly recognises its mate (that is, reacts selectively to it amongst a group of other gulls) from a distance of 30 yards. Nor is the herring gull alone in this respect; similar facts are known about jackdaws, geese, terns, and other birds. Recognition is based partially on visual stimuli, partly on voice.
The fact that many species, man included, seem to distinguish individuals of their own species much more readily than individuals of other species is another aspect of the innate basis of learning.
Other instances of localised learning dispositions have been found in the digger wasp, Philanthus triangulum. Females of this species have innate releasing mechanisms directing the chain of prey-hunting activities to the hive bee alone, among hundreds of other insect species. There is no indication of a conditioning of the hunting pattern, apart, perhaps, from the development of a certain preference for favourable hunting territories. Each wasp, however, learns, with astonishing rapidity and precision, the locality of each new nest it builds.
From RICHARD DAWKINS, The Selfish Gene (1989)
The gene, the DNA molecule, happens to be the replicating entity that prevails on our own planet. There may be others. If there are, provided certain other conditions are met, they will almost inevitably tend to become the basis for an evolutionary process.
But do we have to go to distant worlds to find other kinds of replicator and other, consequent, kinds of evolution? I think that a new kind of replicator has recently emerged on this very planet. It is staring us in the face. It is still in its infancy, still drifting clumsily about in its primeval soup, but already it is achieving evolutionary change at a rate that leaves the old gene panting far behind. The new soup is the soup of human culture. We need a name for the new replicator, a noun that conveys the idea of a unit of cultural transmission, or a unit of imitation. ‘Mimeme’ comes from a suitable Greek root, but I want a monosyllable that sounds a bit like ‘gene’. I hope my classicist friends will forgive me if I abbreviate mimeme to meme. If it is any consolation, it could alternatively be thought of as being related to ‘memory’, or to the French word même. It should be pronounced to rhyme with ‘cream’.
Examples of memes are tunes, ideas, catch-phrases, clothes fashions, ways of making pots or of building arches. Just as genes propagate themselves in the gene pool by leaping from body to body via sperms or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation. If a scientist hears, or reads about, a good idea, he passes it on to his colleagues and students. He mentions it in his articles and his lectures. If the idea catches on, it can be said to propagate itself, spreading from brain to brain. As my colleague N. K. Humphrey neatly summed up an earlier draft of this chapter: ‘… memes should be regarded as living structures, not just metaphorically but technically. When you plant a fertile meme in my mind you literally parasitize my brain, turning it into a vehicle for the meme’s propagation in just the way that a virus may parasitize the genetic mechanism of a host cell. And this isn’t just a way of talking – the meme for, say, “belief in life after death” is actually realized physically, millions of times over, as a structure in the nervous systems of individual men the world over.’
Consider the idea of God. We do not know how it arose in the meme pool. Probably it originated many times by independent ‘mutation’. In any case, it is very old indeed. How does it replicate itself? By the spoken and written word, aided by great music and great art. Why does it have such high survival value? Remember that ‘survival value’ here does not mean value for a gene in a gene pool, but value for a meme in a meme pool. The question really means: what is it about the idea of a god that gives it its stability and penetrance in the cultural environment? The survival value of the god meme in the meme pool results from its great psychological appeal. It provides a superficially plausible answer to deep and troubling questions about existence. It suggests that injustices in this world may be rectified in the next. The ‘everlasting arms’ hold out a cushion against our own inadequacies which, like a doctor’s placebo, is none the less effective for being imaginary. These are some of the reasons why the idea of God is copied so readily by successive generations of individual brains. God exists, if only in the form of a meme with high survival value, or infective power, in the environment provided by human culture.
Some of my colleagues have suggested to me that this account of the survival value of the god meme begs the question. In the last analysis they wish always to go back to ‘biological advantage’. To them it is not good enough to say that the idea of a god has ‘great psychological appeal’. They want to know why it has great psychological appeal. Psychological appeal means appeal to brains, and brains are shaped by natural selection of genes in gene-pools. They want to find some way in which having a brain like that improves gene survival.
From GEORGE JOHNSON, In the Palaces of Memory (1992)
As the digital computer rose to power in the second half of the twentieth century, the localizationist view became dominant. In a computer, memories are stored in very precise locations. Why should it be different in the brain? A number of psychologists were seized by this idea that the mind could be thought of as software running on some sort of biological machine. ‘The mind is what the brain does’ became their battle cry. While this was a neat way to argue against dualism – the idea that the brain is inhabited by a separate, ethereal mind stuff – the biologists were not very impressed. When it came to memory, the computer metaphor was not much more illuminating than its precedessors. After all, a computer doesn’t really remember any more than a video camera sees. In a computer, what passes for memory consists of the 1s and 0s of binary code stored in a bank of transistors, the precursor of the chip, or on a spinning magnetic drum. The computer metaphor was just a fancier version of the video recorder model. Maybe on some level the brain was a kind of computing machine. But nothing explained how it could store such a vast amount of information, not simply recording it but actively arranging and rearranging it into structures, fitting in a new memory among everything else that was already known.
While the computer model of the mind continued to enchant the psychologists, the search for the engram moved to different ground. Inspired by Watson and Crick’s discovery of the double helical structure of the DNA, a few biologists began to consider an entirely different storage site, the molecules inside the brain. If a sequence of molecules called nucleotides – the steps in the helical staircase – could encode the genetic information necessary to make a human, why couldn’t memories be recorded this way? The alphabet of memory would be the letters A, C, T and G – the molecules adenine, cytosine, thymine and guanine that spell the instructions for making enzymes and other proteins, the very substance of life. While it was not at all clear how this four-letter code would spell out a memory, much less a whole childhood experience, the notion of a biological code whose symbols were molecules was hard to resist. How wonderful it would be if evolution had taken the same mechanism used to store a species’ genetic memory and adapted it for use in the brain.
For a while it seemed that this might be the metaphor the neuroscientists were seeking. In 1965 a neurobiologist named Allan Jacobson reported that he had trained rats to react to a flashing light by heading for their food dispensers, where they were rewarded with nourishment. Jacobson killed the animals, extracted RNA (an information-carrying molecule similar to DNA) from their brains, and injected it into the stomachs of untrained rats. Then he would test these animals by flashing a light and seeing how they reacted. Sure enough, Jacobson claimed, the rats would tend to head for the food dispenser, as though they had gone through the training sequence. A memory, it seemed, had been taken from the brain of one rat and squirted into another. The engram appeared to be something that could be carried around in a syringe. In other experiments, worms called Planaria were trained to avoid light, then chopped up and fed to other Planaria, which seemed to inherit the trait.
One researcher, Georges Ungar, insisted that memory was encoded not in nucleic acids but in a different molecular alphabet: the sequence of amino acids that make up protein chains. Working in the early 1970s, he used electrical shocks to train rats to avoid darkness. Then he extracted chemicals from their brains. By analyzing this mixture, he found a proteinlike substance (a polypeptide consisting of eight to fifteen amino acids) that seemed to contain the memory of the electrical shock.
Other rats injected with this molecule, or even a synthesized version of it, also tended to avoid the dark. Ungar called the chemical scotophobin – derived from the Greek words for ‘fear of the dark’ – and claimed to have found similar molecules that carried other memories. A few people imagined the day when pills would replace books. Starving M.B.A. students could sell brain fluid to pharmaceutical companies instead of blood plasma. But most researchers remained skeptical. In all these cases, the evidence was statistical, unconvincing, and impossible to replicate. With Ungar’s death in 1977, research into chemical engrams lapsed into obscurity. Now most neuroscientists believe that scotophobin is to psychology what phlogiston is to chemistry – a figment of the imagination.
From DANIEL L. ALKON, Memory’s Voice: Deciphering the Mind–Brain Code (1994)
