Section 104. (b) Hallucinations and Illusions.
The limits between illusions of sense and hallucinations and
illusions proper can in no sense be definitely determined inasmuch
as any phenomena of the one may be applied to the other, and vice
versa.
[1] Most safely it may be
held that the cause of illusions of
sense lies in the nature of sense-organs, while the hallucinations and
illusions are due to the activity of the brain. The latter are much
more likely to fall within the scope of the physician than sense-illusions,
but at the same time many of them have to be determined
upon by the lawyer, inasmuch as they really occur to normal people
or to such whose disease is just beginning so that the physician can
not yet reach it. Nevertheless, whenever the lawyer finds himself
face to face with a supposed illusion or hallucination he must absolutely
call in the physician. For, as rarely as an ordinary illusion of
sense is explicable by the rules of logic or psychology, or even by
means of other knowledge or experience at the command of any
educated man, so, frequently, do processes occur in cases of hallucination
and illusion which require, at the very least, the physiological
knowledge of the physician. Our activity must hence be limited
to the perception of the presence of hallucination or illusion; the
rest is matter for the psychiatrist. Small as our concern is, it is
important and difficult, for on the one hand we must not appeal to
the physician about every stupid fancy or every lie a prisoner utters,
and on the other hand we assume a heavy responsibility if we interpret
a real hallucination or illusion as a true and real observation.
To acquire knowledge of the nature of these things, therefore, can
not be rigorously enough recommended.
Hallucination and illusion have been distinguished by the fact
that hallucination implies no external object whatever, while in
illusion objects are mistaken and misinterpreted. When one thing
is taken for another, e. g., an oven for a man, the rustle of the wind
for a human song, we have illusion. When no objective existence
is perceived, e. g., when a man is seen to enter, a voice is heard, a
touch is felt, although nothing whatever has happened, we have
hallucination. Illusion is partial, hallucination complete, supplementation
of an external object. There is not a correct and definite
difference between illusion and hallucination inasmuch as what is
present may be so remotely connected with what is perceived that it
is no more than a stimulus, and thus illusion may be turned into
real hallucination. One authority calls illusion the conception of
an actually present external event which is perceived by the peripheral
organs in the form of an idea that does not coincide with the
event. The mistake does not lie in the defective activity of the
senses so much as in the fact that an apperceptive idea is substituted
for the perceptive view. In hallucination every external event is
absent, and hence, what is seen is due to a stimulation of the periphery.
Some authorities believe hallucination to be caused by
cramp of the sensory nerve. Others find illusions to be an externally
stimulated sense-perception not corresponding to the stimulus, and
still others believe it to be essentially normal. Most human beings
are from time to time subject to illusions; indeed, nobody is always
sober and intelligent in all his perceptions and convictions. The
luminous center of our intelligent perceptions is wrapped in a cloudy
half-shadow of illusion.
Sully[2] aims to distinguish
the essential nature of illusion from
that characterized by ordinary language. Illusion, according to
him, is often used to denote mistakes which do not imply untrue
perceptions. We say a man has an illusion who thinks too much of
himself, or when he tells stories otherwise than as they happen
because of a weakness of memory. Illusion is every form of mistake
which substitutes any direct self-evident or intuitive knowledge,
whether as sense-perception or as any other form.
Nowadays the cause of hallucination and illusion is sought in
the over-excitement of the cerebro-spinal system. As this stimulation
may be very various in its intensity and significance, from the
momentary rush of blood to complete lunacy, so hallucinations and
illusions may be insignificant or signs of very serious mental
disturbances. When we seek the form of these phenomena, we find
that all those psychical events belong to it which have not been
purposely performed or lied about. When Brutus
sees Cæsar's
ghost; Macbeth, Banquo's ghost; Nicholas, his son; these are
distinctly hallucinations or illusions of the same kind as those
"really and truly" seen by our nurses. The stories of such people
have no significance for the criminalist, but if a person has seen an
entering thief, an escaping murderer, a bloody corpse, or some
similar object of criminal law, and these are hallucinations like classical
ghosts, then are we likely to be much deceived.
Hoppe[3] enumerates
hallucinations of apparently sound (?) people. 1. A priest
tired by mental exertion, saw, while he was writing, a boy's head
look over his shoulder. If he turned toward it it disappeared, if
he resumed writing it reappeared. 2. "A thoroughly intelligent"
man always was seeing a skeleton. 3. Pascal, after a heavy blow,
saw a fiery abyss into which he was afraid he would fall. 4. A man
who had seen an enormous fire, for a long time afterward saw flames
continually. 5. Numerous cases in which criminals, especially
murderers, always had their victims before their eyes. 6. Justus
Möser saw well-known flowers and geometrical figures very distinctly.
7. Bonnet knows a "healthy" man who saw people, birds,
etc., with open eyes. 8. A man got a wound in his left ear and
for weeks afterward saw a cat. 9. A woman eighty-eight years old
often saw everything covered with flowers,—otherwise she was
quite "well."
A part of these stories seems considerably fictitious, a part applies
to indubitable pathological cases, and certain of them are confirmed
elsewhere. That murderers, particularly women-murderers of
children, often see their victims is well known to us criminalists.
And for this reason the habit of confining prisoners in a dark cell for
twenty-four hours on the anniversary of a crime must be pointed to
as refined and thoroughly mediæval cruelty. I have repeatedly
heard from people so tortured of the terror of their visions on such
days of martyrdom. Cases are told of in which prisoners who were
constipated had all kinds of visual and auditory hallucinations and
appeared, e. g., to hear in the rustling of their straw, all sorts of
words. That isolation predisposes people to such things is as well
known as the fact that constipation causes a rush of blood to the
head, and hence, nervous excitement. The well-known stories of
robbers which are often told us by prisoners are not always the fruit
of malicious invention. Probably a not insignificant portion are
the result of hallucination.
Hoppe tells of a great group of hallucinations in conditions of
waking and half-waking, and asserts that everybody has them and
can note them if he gives his attention thereto. This may be an
exaggeration, but it is true that a healthy person in any way excited
or afraid may hear all kinds of things in the crackling of a fire, etc.,
and may see all kinds of things, in smoke, in clouds, etc. The movement
of portraits and statues is particularly characteristic, especially
in dim light, and under unstable emotional conditions. I own a
relief by Ghiberti called the "Rise of the Flesh," in which seven
femurs dance around a corpse and sing. If, at night, I put out the
lamp in my study and the moon falls on the work, the seven femurs
dance as lively as may be during the time it takes my eyes to adapt
themselves from the lamplight to the moonlight. Something similar
I see on an old carved dresser. The carving is so delicate that in
dim light it shows tiny heads and flames after the fashion of the
Catholic church pictures of "poor souls," in purgatory. Under
certain conditions of illumination the flames flicker, the heads move,
and out of the fire the arms raise themselves to the clouds floating
above. Now this requires no unusual excitement, simply the weary
sensing of evening, when the eyes turn from prolonged uniform
reading or writing to something
else.
[4] It has happened to me from
my earliest childhood. High bodily temperature may easily cause
hallucinations. Thus, marching soldiers are led to shoot at
non-existing animals and apparently-approaching enemies. Uniform
and fatiguing mental activity is also a source of hallucination.
Fechner says that one day having performed a long experiment
with the help of a stop-watch, he heard its beats through the whole
evening after. So again when he was studying long series of figures
he used to see them at night in the dark so distinctly that he could
read them off.
Then there are illusions of touch which may be criminalistically
important. A movement of air may be taken for an approaching
man. A tight collar or cravat may excite the image of being stifled!
Old people frequently have a sandy taste while eating,—when this
is told the thought occurs that it may be due to coarsely powdered
arsenic, yet it may be merely illusion.
The slightest abnormality makes hallucinations and illusions very
easy. Persons who are in great danger have all kinds of hallucinations,
particularly of people. In the court of law, when witnesses
who have been assaulted testify to having seen people, hallucination
may often be the basis of their evidence. Hunger again, or loss of
blood, gives rise to the most various hallucinations. Menstruation
and hæmorrhoids may be the occasions of definite periodic visions,
and great pain may be accompanied by hallucinations which begin
with the pain, become more distinct as it increases, and disappear
when it ceases.
It might seem that in this matter, also, the results are destructive
and that the statements of witnesses are untrue and unreliable. I
do not assert that our valuation of these statements shall be checked
from all possible directions, but I do say that much of what we
have considered as true depends only on illusions in the broad sense
of the word and that it is our duty before all things rigorously to
test everything that underlies our researches.
[[ id="n104.1"]]
C. Wernicke Über Halluzinationen, Ratlosigkeit, Desorientierung etc.
Monatschrift f. Psychiatrie u. Neurologie, IX, 1 (1901).
[[ id="n104.2"]]
James Sully. Illusions.
[[ id="n104.3"]]
J, J. Hoppe. Erklärungen des Sinnestauschungen.
[[ id="n104.4"]]
Cf. A. Mosso: Die Ermüdung. Leipzig 1892.