Lecture IV - Influence of Past History on Present Occurrences in Living Organisms

Lecture IV - Influence of Past History on Present Occurrences in Living Organisms

In this lecture we shall be concerned with a very general

characteristic which broadly, though not absolutely,

distinguishes the behaviour of living organisms from that of dead

matter. The characteristic in question is this:

The response of an organism to a given stimulus is very often

dependent upon the past history of the organism, and not merely

upon the stimulus and the HITHERTO DISCOVERABLE present state of

the organism.

This characteristic is embodied in the saying "a burnt child

fears the fire." The burn may have left no visible traces, yet it

modifies the reaction of the child in the presence of fire. It is

customary to assume that, in such cases, the past operates by

modifying the structure of the brain, not directly. I have no

wish to suggest that this hypothesis is false; I wish only to

point out that it is a hypothesis. At the end of the present

lecture I shall examine the grounds in its favour. If we confine

ourselves to facts which have been actually observed, we must say

that past occurrences, in addition to the present stimulus and

the present ascertainable condition of the organism, enter into

the causation of the response.

The characteristic is not wholly confined to living organisms.

For example, magnetized steel looks just like steel which has not

been magnetized, but its behaviour is in some ways different. In

the case of dead matter, however, such phenomena are less

frequent and important than in the case of living organisms, and

it is far less difficult to invent satisfactory hypotheses as to

the microscopic changes of structure which mediate between the

past occurrence and the present changed response. In the case of

living organisms, practically everything that is distinctive both

of their physical and of their mental behaviour is bound up with

this persistent influence of the past. Further, speaking broadly,

the change in response is usually of a kind that is biologically

advantageous to the organism.

Following a suggestion derived from Semon ("Die Mneme," Leipzig,

1904; 2nd edition, 1908, English translation, Allen & Unwin,

1921; "Die mnemischen Empfindungen," Leipzig, l909), we will give

the name of "mnemic phenomena" to those responses of an organism

which, so far as hitherto observed facts are concerned, can only

be brought under causal laws by including past occurrences in the

history of the organism as part of the causes of the present

response. I do not mean merely--what would always be the

case--that past occurrences are part of a CHAIN of causes leading

to the present event. I mean that, in attempting to state the

PROXIMATE cause of the present event, some past event or events

must be included, unless we take refuge in hypothetical

modifications of brain structure.) For example: you smell

peat-smoke, and you recall some occasion when you smelt it

before. The cause of your recollection, so far as hitherto observ

able phenomena are concerned, consists both of the peat smoke

(present stimulus) and of the former occasion (past experience).

The same stimulus will not produce the same recollection in

another man who did not share your former experience, although

the former experience left no OBSERVABLE traces in the structure

of the brain. According to the maxim "same cause, same effect,"

we cannot therefore regard the peat-smoke alone as the cause of

your recollection, since it does not have the same effect in

other cases. The cause of your recollection must be both the

peat-smoke and the past occurrence. Accordingly your recollection

is an instance of what we are calling "mnemic phenomena."

Before going further, it will be well to give illustrations of

different classes of mnemic phenomena.

(a) ACQUIRED HABITS.--In Lecture II we saw how animals can learn

by experience how to get out of cages or mazes, or perform other

actions which are useful to them but not provided for by their

instincts alone. A cat which is put into a cage of which it has

had experience behaves differently from the way in which it

behaved at first. We can easily invent hypotheses, which are

quite likely to be true, as to connections in the brain caused by

past experience, and themselves causing the different response.

But the observable fact is that the stimulus of being in the cage

produces differing results with repetition, and that the

ascertainable cause of the cat's behaviour is not merely the cage

and its own ascertainable organization, but also its past history

in regard to the cage. From our present point of view, the matter

is independent of the question whether the cat's behaviour is due

to some mental fact called "knowledge," or displays a merely

bodily habit. Our habitual knowledge is not always in our minds,

but is called up by the appropriate stimuli. If we are asked

"What is the capital of France?" we answer "Paris," because of

past experience; the past experience is as essential as the

present question in the causation of our response. Thus all our

habitual knowledge consists of acquired habits, and comes under

the head of mnemic phenomena.

(b) IMAGES.--I shall have much to say about images in a later

lecture; for the present I am merely concerned with them in so

far as they are "copies" of past sensations. When you hear New

York spoken of, some image probably comes into your mind, either

of the place itself (if you have been there), or of some picture

of it (if you have not). The image is due to your past

experience, as well as to the present stimulus of the words "New

York." Similarly, the images you have in dreams are all dependent

upon your past experience, as well as upon the present stimulus

to dreaming. It is generally believed that all images, in their

simpler parts, are copies of sensations; if so, their mnemic

character is evident. This is important, not only on its own

account, but also because, as we shall see later, images play an

essential part in what is called "thinking."

(c) ASSOCIATION.--The broad fact of association, on the mental

side, is that when we experience something which we have

experienced before, it tends to call up the context of the former

experience. The smell of peat-smoke recalling a former scene is

an instance which we discussed a moment ago. This is obviously a

mnemic phenomenon. There is also a more purely physical

association, which is indistinguishable from physical habit. This

is the kind studied by Mr. Thorndike in animals, where a certain

stimulus is associated with a certain act. This is the sort which

is taught to soldiers in drilling, for example. In such a case

there need not be anything mental, but merely a habit of the

body. There is no essential distinction between association and

habit, and the observations which we made concerning habit as a

mnemic phenomenon are equally applicable to association.

(d) NON-SENSATIONAL ELEMENTS IN PERCEPTION.--When we perceive any

object of a familiar kind, much of what appears subjectively to

be immediately given is really derived from past experience. When

we see an object, say a penny, we seem to be aware of its "real"

shape we have the impression of something circular, not of

something elliptical. In learning to draw, it is necessary to

acquire the art of representing things according to the

sensation, not according to the perception. And the visual

appearance is filled out with feeling of what the object would be

like to touch, and so on. This filling out and supplying of the

"real" shape and so on consists of the most usual correlates of

the sensational core in our perception. It may happen that, in

the particular case, the real correlates are unusual; for

example, if what we are seeing is a carpet made to look like

tiles. If so, the non-sensational part of our perception will be

illusory, i.e. it will supply qualities which the object in

question does not in fact have. But as a rule objects do have the

qualities added by perception, which is to be expected, since

experience of what is usual is the cause of the addition. If our

experience had been different, we should not fill out sensation

in the same way, except in so far as the filling out is

instinctive, not acquired. It would seem that, in man, all that

makes up space perception, including the correlation of sight and

touch and so on, is almost entirely acquired. In that case there

is a large mnemic element in all the common perceptions by means

of which we handle common objects. And, to take another kind of

instance, imagine what our astonishment would be if we were to

hear a cat bark or a dog mew. This emotion would be dependent

upon past experience, and would therefore be a mnemic phenomenon

according to the definition.

(e) MEMORY AS KNOWLEDGE.--The kind of memory of which I am now

speaking is definite knowledge of some past event in one's own

experience. From time to time we remember things that have

happened to us, because something in the present reminds us of

them. Exactly the same present fact would not call up the same

memory if our past experience had been different. Thus our

remembering is caused by--

(1) The present stimulus,

(2) The past occurrence.

It is therefore a mnemic phenomenon according to our definition.

A definition of "mnemic phenomena" which did not include memory

would, of course, be a bad one. The point of the definition is

not that it includes memory, but that it includes it as one of a

class of phenomena which embrace all that is characteristic in

the subject matter of psychology.

(f) EXPERIENCE.--The word "experience" is often used very

vaguely. James, as we saw, uses it to cover the whole primal

stuff of the world, but this usage seems objection able, since,

in a purely physical world, things would happen without there

being any experience. It is only mnemic phenomena that embody

experience. We may say that an animal "experiences" an occurrence

when this occurrence modifies the animal's subsequent behaviour,

i.e. when it is the mnemic portion of the cause of future

occurrences in the animal's life. The burnt child that fears the

fire has "experienced" the fire, whereas a stick that has been

thrown on and taken off again has not "experienced" anything,

since it offers no more resistance than before to being thrown

on. The essence of "experience" is the modification of behaviour

produced by what is experienced. We might, in fact, define one

chain of experience, or one biography, as a series of occurrences

linked by mnemic causation. I think it is this characteristic,

more than any other, that distinguishes sciences dealing with

living organisms from physics.

The best writer on mnemic phenomena known to me is Richard Semon,

the fundamental part of whose theory I shall endeavour to

summarize before going further:

When an organism, either animal or plant, is subjected to a

stimulus, producing in it some state of excitement, the removal

of the stimulus allows it to return to a condition of

equilibrium. But the new state of equilibrium is different from

the old, as may be seen by the changed capacity for reaction. The

state of equilibrium before the stimulus may be called the

"primary indifference-state"; that after the cessation of the

stimulus, the "secondary indifference-state." We define the

"engraphic effect" of a stimulus as the effect in making a

difference between the primary and secondary indifference-states,

and this difference itself we define as the "engram" due to the

stimulus. "Mnemic phenomena" are defined as those due to engrams;

in animals, they are specially associated with the nervous

system, but not exclusively, even in man.

When two stimuli occur together, one of them, occurring

afterwards, may call out the reaction for the other also. We call

this an "ekphoric influence," and stimuli having this character

are called "ekphoric stimuli." In such a case we call the engrams

of the two stimuli "associated." All simultaneously generated

engrams are associated; there is also association of successively

aroused engrams, though this is reducible to simultaneous

association. In fact, it is not an isolated stimulus that leaves

an engram, but the totality of the stimuli at any moment;

consequently any portion of this totality tends, if it recurs, to

arouse the whole reaction which was aroused before. Semon holds

that engrams can be inherited, and that an animal's innate habits

may be due to the experience of its ancestors; on this subject he

refers to Samuel Butler.

Semon formulates two "mnemic principles." The first, or "Law of

Engraphy," is as follows: "All simultaneous excitements in an

organism form a connected simultaneous excitement-complex, which

as such works engraphically, i.e. leaves behind a connected

engram-complex, which in so far forms a whole" ("Die mnemischen

Empfindungen," p. 146). The second mnemic principle, or "Law of

Ekphory," is as follows: "The partial return of the energetic

situation which formerly worked engraphically operates

ekphorically on a simultaneous engram-complex" (ib., p. 173).

These two laws together represent in part a hypothesis (the

engram), and in part an observable fact. The observable fact is

that, when a certain complex of stimuli has originally caused a

certain complex of reactions, the recurrence of part of the

stimuli tends to cause the recurrence of the whole of the

reactions.

Semon's applications of his fundamental ideas in various

directions are interesting and ingenious. Some of them will

concern us later, but for the present it is the fundamental

character of mnemic phenomena that is in question.

Concerning the nature of an engram, Semon confesses that at

present it is impossible to say more than that it must consist in

some material alteration in the body of the organism ("Die

mnemischen Empfindungen," p. 376). It is, in fact, hypothetical,

invoked for theoretical uses, and not an outcome of direct

observation. No doubt physiology, especially the disturbances of

memory through lesions in the brain, affords grounds for this

hypothesis; nevertheless it does remain a hypothesis, the

validity of which will be discussed at the end of this lecture.

I am inclined to think that, in the present state of physiology,

the introduction of the engram does not serve to simplify the

account of mnemic phenomena. We can, I think, formulate the known

laws of such phenomena in terms, wholly, of observable facts, by

recognizing provisionally what we may call "mnemic causation." By

this I mean that kind of causation of which I spoke at the

beginning of this lecture, that kind, namely, in which the

proximate cause consists not merely of a present event, but of

this together with a past event. I do not wish to urge that this

form of causation is ultimate, but that, in the present state of

our knowledge, it affords a simplification, and enables us to

state laws of behaviour in less hypothetical terms than we should

otherwise have to employ.

The clearest instance of what I mean is recollection of a past

event. What we observe is that certain present stimuli lead us to

recollect certain occurrences, but that at times when we are not

recollecting them, there is nothing discoverable in our minds

that could be called memory of them. Memories, as mental facts,

arise from time to time, but do not, so far as we can see, exist

in any shape while they are "latent." In fact, when we say that

they are "latent," we mean merely that they will exist under

certain circumstances. If, then, there is to be some standing

difference between the person who can remember a certain fact and

the person who cannot, that standing difference must be, not in

anything mental, but in the brain. It is quite probable that

there is such a difference in the brain, but its nature is

unknown and it remains hypothetical. Everything that has, so far,

been made matter of observation as regards this question can be

put together in the statement: When a certain complex of

sensations has occurred to a man, the recurrence of part of the

complex tends to arouse the recollection of the whole. In like

manner, we can collect all mnemic phenomena in living organisms

under a single law, which contains what is hitherto verifiable in

Semon's two laws. This single law is:

IF A COMPLEX STIMULUS A HAS CAUSED A COMPLEX REACTION B IN AN

ORGANISM, THE OCCURRENCE OF A PART OF A ON A FUTURE OCCASION

TENDS TO CAUSE THE WHOLE REACTION B.

This law would need to be supplemented by some account of the

influence of frequency, and so on; but it seems to contain the

essential characteristic of mnemic phenomena, without admixture

of anything hypothetical.

Whenever the effect resulting from a stimulus to an organism

differs according to the past history of the organism, without

our being able actually to detect any relevant difference in its

present structure, we will speak of "mnemic causation," provided

we can discover laws embodying the influence of the past. In

ordinary physical causation, as it appears to common sense, we

have approximate uniformities of sequence, such as "lightning is

followed by thunder," "drunkenness is followed by headache," and

so on. None of these sequences are theoretically invariable,

since something may intervene to disturb them. In order to obtain

invariable physical laws, we have to proceed to differential

equations, showing the direction of change at each moment, not

the integral change after a finite interval, however short. But

for the purposes of daily life many sequences are to all in tents

and purposes invariable. With the behaviour of human beings,

however, this is by no means the case. If you say to an

Englishman, "You have a smut on your nose," he will proceed to

remove it, but there will be no such effect if you say the same

thing to a Frenchman who knows no English. The effect of words

upon the hearer is a mnemic phenomena, since it depends upon the

past experience which gave him understanding of the words. If

there are to be purely psychological causal laws, taking no

account of the brain and the rest of the body, they will have to

be of the form, not "X now causes Y now," but--

"A, B, C, . . . in the past, together with X now, cause Y now."

For it cannot be successfully maintained that our understanding

of a word, for example, is an actual existent content of the mind

at times when we are not thinking of the word. It is merely what

may be called a "disposition," i.e. it is capable of being

aroused whenever we hear the word or happen to think of it. A

"disposition" is not something actual, but merely the mnemic

portion of a mnemic causal law.

In such a law as "A, B, C, . . . in the past, together with X

now, cause Y now," we will call A, B, C, . . . the mnemic cause,

X the occasion or stimulus, and Y the reaction. All cases in

which experience influences behaviour are instances of mnemic

causation.

Believers in psycho-physical parallelism hold that psychology can

theoretically be freed entirely from all dependence on physiology

or physics. That is to say, they believe that every psychical

event has a psychical cause and a physical concomitant. If there

is to be parallelism, it is easy to prove by mathematical logic

that the causation in physical and psychical matters must be of

the same sort, and it is impossible that mnemic causation should

exist in psychology but not in physics. But if psychology is to

be independent of physiology, and if physiology can be reduced to

physics, it would seem that mnemic causation is essential in

psychology. Otherwise we shall be compelled to believe that all

our knowledge, all our store of images and memories, all our

mental habits, are at all times existing in some latent mental

form, and are not merely aroused by the stimuli which lead to

their display. This is a very difficult hypothesis. It seems to

me that if, as a matter of method rather than metaphysics, we

desire to obtain as much independence for psychology as is

practically feasible, we shall do better to accept mnemic

causation in psychology protem, and therefore reject parallelism,

since there is no good ground for admitting mnemic causation in

physics.

It is perhaps worth while to observe that mnemic causation is

what led Bergson to deny that there is causation. at all in the

psychical sphere. He points out, very truly, that the same

stimulus, repeated, does not have the same consequences, and he

argues that this is contrary to the maxim, "same cause, same

effect." It is only necessary, however, to take account of past

occurrences and include them with the cause, in order to

re-establish the maxim, and the possibility of psychological

causal laws. The metaphysical conception of a cause lingers in

our manner of viewing causal laws: we want to be able to FEEL a

connection between cause and effect, and to be able to imagine

the cause as "operating." This makes us unwilling to regard

causal laws as MERELY observed uniformities of sequence; yet that

is all that science has to offer. To ask why such-and-such a kind

of sequence occurs is either to ask a meaningless question, or to

demand some more general kind of sequence which includes the one

in question. The widest empirical laws of sequence known at any

time can only be "explained" in the sense of being subsumed by

later discoveries under wider laws; but these wider laws, until

they in turn are subsumed, will remain brute facts, resting

solely upon observation, not upon some supposed inherent

rationality.

There is therefore no a priori objection to a causal law in which

part of the cause has ceased to exist. To argue against such a

law on the ground that what is past cannot operate now, is to

introduce the old metaphysical notion of cause, for which science

can find no place. The only reason that could be validly alleged

against mnemic causation would be that, in fact, all the

phenomena can be explained without it. They are explained without

it by Semon's "engram," or by any theory which regards the

results of experience as embodied in modifications of the brain

and nerves. But they are not explained, unless with extreme

artificiality, by any theory which regards the latent effects of

experience as psychical rather than physical. Those who desire to

make psychology as far as possible independent of physiology

would do well, it seems to me, if they adopted mnemic causation.

For my part, however, I have no such desire, and I shall

therefore endeavour to state the grounds which occur to me in

favour of some such view as that of the "engram."

One of the first points to be urged is that mnemic phenomena are

just as much to be found in physiology as in psychology. They are

even to be found in plants, as Sir Francis Darwin pointed out

(cf. Semon, "Die Mneme," 2nd edition, p. 28 n.). Habit is a

characteristic of the body at least as much as of the mind. We

should, therefore, be compelled to allow the intrusion of mnemic

causation, if admitted at all, into non-psychological regions,

which ought, one feels, to be subject only to causation of the

ordinary physical sort. The fact is that a great deal of what, at

first sight, distinguishes psychology from physics is found, on

examination, to be common to psychology and physiology; this

whole question of the influence of experience is a case in point.

Now it is possible, of course, to take the view advocated by

Professor J. S. Haldane, who contends that physiology is not

theoretically reducible to physics and chemistry.* But the weight

of opinion among physiologists appears to be against him on this

point; and we ought certainly to require very strong evidence

before admitting any such breach of continuity as between living

and dead matter. The argument from the existence of mnemic

phenomena in physiology must therefore be allowed a certain

weight against the hypothesis that mnemic causation is ultimate.

* See his "The New Physiology and Other Addresses," Griffin,

1919, also the symposium, "Are Physical, Biological and

Psychological Categories Irreducible?" in "Life and Finite

Individuality," edited for the Aristotelian Society, with an

Introduction. By H. Wildon Carr, Williams & Norgate, 1918.

The argument from the connection of brain-lesions with loss of

memory is not so strong as it looks, though it has also, some

weight. What we know is that memory, and mnemic phenomena

generally, can be disturbed or destroyed by changes in the brain.

This certainly proves that the brain plays an essential part in

the causation of memory, but does not prove that a certain state

of the brain is, by itself, a sufficient condition for the

existence of memory. Yet it is this last that has to be proved.

The theory of the engram, or any similar theory, has to maintain

that, given a body and brain in a suitable state, a man will have

a certain memory, without the need of any further conditions.

What is known, however, is only that he will not have memories if

his body and brain are not in a suitable state. That is to say,

the appropriate state of body and brain is proved to be necessary

for memory, but not to be sufficient. So far, therefore, as our

definite knowledge goes, memory may require for its causation a

past occurrence as well as a certain present state of the brain.

In order to prove conclusively that mnemic phenomena arise

whenever certain physiological conditions are fulfilled, we ought

to be able actually to see differences between the brain of a man

who speaks English and that of a man who speaks French, between

the brain of a man who has seen New York and can recall it, and

that of a man who has never seen that city. It may be that the

time will come when this will be possible, but at present we are

very far removed from it. At present, there is, so far as I am

aware, no good evidence that every difference between the

knowledge possessed by A and that possessed by B is paralleled by

some difference in their brains. We may believe that this is the

case, but if we do, our belief is based upon analogies and

general scientific maxims, not upon any foundation of detailed

observation. I am myself inclined, as a working hypothesis, to

adopt the belief in question, and to hold that past experience

only affects present behaviour through modifications of

physiological structure. But the evidence seems not quite

conclusive, so that I do not think we ought to forget the other

hypothesis, or to reject entirely the possibility that mnemic

causation may be the ultimate explanation of mnemic phenomena. I

say this, not because I think it LIKELY that mnemic causation is

ultimate, but merely because I think it POSSIBLE, and because it

often turns out important to the progress of science to remember

hypotheses which have previously seemed improbable.

__________

End of Lecture IV - Influence of Past History on Present Occurrences in Living Organisms [Bertrand Russell's essay/lecture: The Analysis of Mind]

Read next: Lecture V - Psychological and Physical Causal Laws

Read previous: Lecture III - Desire and Feeling

Table of content of Analysis of Mind



GO TO TOP OF SCREEN

Post your review
Your review will be placed after the table of content of this book