THE first case here reported came to the notice of the writer through the
attending physician; the second case was reported by the father of the child
after the attending physician had failed of satisfactory treatment. The
second case is especially interesting and serviceable in connection with the
phenomenon of visual space perception.
The first case is that of a boy, nine years of age, healthy, vigorous, who
in his play ground and street reactions parallels that of any normal boy of
his age. Aside from measles and an occasional disturbance of digestion he
has been singularly free from childhood's common diseases. The father and
mother are strong Hanoverian Germans holding with puritanic strictness to
the dogmas of the Lutheran religious faith. So far as is ascertainable there
can be no question of faulty inheritance, at least not so far as the
immediate parents and grandparents enter into the problem.
The child upon retiring and usually while still wide awake uttered wild
screams of terror. Upon inquiry the child complained of falling and
clutched vigorously to the bed clothes and the arms of the parents. Usually
the phenomenon disappeared when he was taken out of bed and walked about but
reappeared when he lay down. He complained of pain in his eyes, neck and
fore- and after-parts of his head. No amount of persuasion dispelled the
illusion. It should be emphasized that the illusion occurred in full waking
state and rarely as a dream.
An attempt was made to correlate the illusion with the momentum of the day's
activity. According to the parents the illusion appeared in aggravated form
when the neighborhood boys congregated in a cluster of trees at the edge of
the village and when playing "train" in which case the barn-top functioned
as the locomotive while a high board fence and an adjoining neighbor's barn
functioned as the cars and caboose respectively.
The village physician offered no explanation. He prescribed a hot bath and
a "closer supervision of the evening meal." The dilatation of the cutaneous
capillaries consequent to the bath lowered the cerebral circulation and to
some extent reduced the intensity of the illusion.
The cue to the cure appeared when the child, in expressing his fear,
complained because he could not see the parent who sat beside him on the
bed. Upon lighting the room the child seemed pacified but still held tightly
to anything within reach. As a rule the illusion disappeared within thirty
minutes after illumination. It was then suggested that the child be put to
bed in a well lighted room. This was done but the phenomenon reappeared
although in a less aggravated form. Degree of illumination and intensity of
the illusion appeared related. The phenomenon failed to appear at all when a
coal oil lamp was placed beside the bed not over two feet from the child's
head. For six months the boy went to sleep facing the full glare of the
lamp. Gradually the lamp was removed until it occupied a position in the
hall. Whenever the illusion recurred the lamp was replaced in its original
position.
It is quite probable that the intensity of the visual stimulus (the lamp)
deflected the nervous current from the neural processes underlying the
illusion and thus changed the direction of attention. Any intense
distraction, other than the one employed, would probably have served the
same purpose. At the end of a year and a half the phenomenon entirely
disappeared.
The second case is that of a six-year-old girl, the daughter of highly
educated parents. With reference to this case two interesting phenomena
were observed: (a) that of mirror-writing of the common variety and (b)
that of ambiguous interpretation of the retinal impressions.
The phenomenon of mirror-writing here observed parallels that of many other
cases in which the left-right direction is reversed. These commoner cases
take on an added interest when considered in connection with a case of
double space inversion. Such a case is on record.[1] The double inversion
consists in writing all verbal symbols and digits up side down and backward.
In this case the boy had perfect pseudoscopic vision at the beginning of his
school work. Stratton, by a system of lenses, artificially produces the
same distortions and throws some light on the phenomenon.[2]
[1] G. F. Arps, a Note on a Case of Double Space Inversion. Annals of
Ophthalmology, July, 1914, Vol. XXIII, p. 482.
[2] Psychological Review, Vol. IV, pp. 341-360 and 463-481.
It is in the phenomenon of ambiguity in the interpretation of the retinal
eye processes that this case finds its value. At the dinner table the child
complained of the decrease in size of a number of objects in the room,
especially was this true of the apparent size of the father's head. The
frequency of the complaint led the father to seek the advice of an occulist
who pronounced the child's vision perfect in every way. Over and over again
while seated at the dinner table the child would exclaim, "O father how
small your head is!"
The explanation of this phenomenon is found in the method employed to
dispell the illusion. It was suggested that, at the moment of the
appearance of the phenomenon, the child be requested to fixate the end of
the father's index finger which was revolved, in the air, to form various
geometrical figures. This had the desired effect. Clearly we have here a
case of the object altering its apparent size without altering its distance.
Under normal conditions a change in size is followed by a corresponding
change in the distance. It is probable that we have here inadequate
convergence and that the optic axes do not intersect at the object but
beyond, so that the axes are more or less parallel. Thus the feeling of
convergence is less intense than experience teaches is necessary to perceive
the object as such a size and at such a distance. If degree of convergence
is a criterion for distance and if distance is a measure for the apparent
size of an object then we have the conditions necessary for the appearance
of the illusion.
Here we have the retinal image constant for the apparent and the real size
of the object (head). Obviously the retinal processes are constant for the
two interpretations of magnitude and the ambiguity is due to the concomitant
factor of convergence.
The conditions necessary to decrease the real size of an object while still
maintaining an unaltered image are produced without artificial means.
Wheatstone, a long time ago, arranged his stereoscope so that a negative
correlation obtained between the degree of convergence and size of the
retinal image.[3]
[3] Philosophical Transactions, 1852.
Very interesting is the fact that Stratton demonstrated by artificial means
what was naturally the case in that of the boy reported in the Annals
referred to above. Wheatstone demonstrated by artificial means what was
naturally the case in that of the girl here reported.