One of them is the order with which we found the machine theory
occupied in its effort to explain how a given local process is properly
placed between its neighbors, and not confused therewith. However,
there is another order in the field which has escaped the attention of
many psychologists, though it is not less important than the first. In
most visual fields the contents of certain areas “belong together,”
so that we have circumscribed, or bounded, units before us, from
which their surroundings are excluded. If James did not admit this
organization of the field as a sensory fact, the reason for it was the
enormous power of the theory of meaning, which has been an obdurate
obstacle to our seeing important problems, more in this connection
than elsewhere. For the same reason there may be only a few readers
who will not quarrel with the next paragraphs as long as they see any
possibility of so doing.
When I look at the desk before me I find quite a number of
circumscribed units which appear detached and segregated in the field:
a piece of paper as against the surface of the desk, a pencil, an
eraser, a cigarette, and so forth. In all these cases there are two
mutually dependent conditions. The existence of a unit involves its
segregation from its surroundings. In order to satisfy myself that
I am here talking about realities, I may try to form other units
consisting of parts of those objects and parts of their environment
taken together. In some cases my attempt will be a complete failure. In
others, where, for some reason, there is greater success, the result is
so strange that it indicates by contrast what a specific reality the
original organization was.
But the reader says: Of course, you are somehow talking about
realities. Still, something may be real psychologically without
belonging to sensory experience proper. How can you forget for a moment
that a piece of paper, a pencil, a cigarette, are objects known by use!
You have handled them during many years and so you had more opportunity
than you needed for learning that they _behave_ practically as units.
This previous experience being projected into your field of vision,
why do you lay so much stress upon a simple fact which is widely known
and well explained, and which has been accounted for ever since, or
probably even before, Aristotle wrote his textbook of psychology. My
answer will be more extensive than this argument. Until we are able
to prevent such superficial applications of the meaning principle,
there can be little agreement about the most elementary problems of
_gestalt_ psychology. Who in the world would deny that a piece of
paper, a pencil, and so on, are well-known objects? That I know their
uses and their names by previous experience and that hence they are
full of “meaning,” shall also be granted without hesitation. But from
these facts there is a large step to the statement that neither the
paper nor the pencil would exist _as segregated units_ in my visual
field without that previous knowledge about their practical behavior
and use. It may be that before I had that knowledge the same things
occurred in the sensory field as units, unknown and unnamed, but still
as segregated wholes. When I see a _green_ object, I can tell the name
of the color immediately; furthermore I know that green is used as a
signal on railroad tracks and also as a symbol of hope. But I do not
believe that, therefore, the color green _as such_ must be explained
by meaning. Existing independently it has acquired several secondary
properties in my lifetime and I agree with the reader in praising all
the advantages which this kind of learning holds for all of us. In
exactly the same manner, sensory units may have acquired names and may
have become richly symbolic in the context of our knowledge, while
existing, nevertheless, as segregated units in the sensory field prior
to such accretions. Such is the conception which _gestalt_ psychology
offers to defend. It even goes so far as to hold that it is precisely
the original organization and segregation of circumscribed wholes which
make it possible for the sensory world to appear so utterly imbued
with meaning to the adult, because, in its gradual entrance into the
sensory field, meaning follows the lines drawn by natural organization.
It usually enters into segregated wholes.
If the explanation by meaning were correct, wholes should be segregated
in the field only insofar as they are recognized as definite known
objects. But this is not the case. Looking into a dark corner or
walking through mist in the evening, the reader will frequently have
found before him an unknown something, detached from its environment
as one whole, the use or the meaning of which he did not discover
until after a more detailed observation. Walking through an unknown
country at night, I have often had such an unrecognized whole in the
field for several minutes. It is evident to me, therefore, that my
knowledge about the practical behavior of things does not determine
their existence as detached units. The same argument may be restated in
a more general form. Whenever we say to ourselves or others: Now, look
here! What may that something there be, at the foot of that hill, just
to the right of the next tree, between those two houses, and so on?--we
ask about the meaning or the use of that something, demonstrating by
our very question that segregation is independent of knowledge and
meaning. As, in physics, a molecule is segregated as a functional unit,
so definite wholes seem to be dynamically detached in the sensory field.
But so fond are we of our empiristic convictions that, in this
predicament, the explanation by meaning will immediately assume another
form. Your unknown whole, seen in the mist, so the reader will say,
appears as something separate, because it is darker, for instance, than
the gray mist around. I admit that no _special_ knowledge about this
definite group of sensations, as meaning a particular object through
past experience, is needed for unifying and segregating it. But you
under-rate the wonderful achievements of previous experience if you
restrict its effects to particular cases. We have always observed that
a set of adjacent sensations, possessing almost the same quality,
different from that of the environment, “behave together,” i.e., move
and are moved, appear and disappear, at the same time. This is the case
with stones, with papers, with hats, with boots, with many animals,
with leaves. As physical objects they are bound together, so that
physically they move as units. It is only one example of the well-known
generalizing power of memory if now we treat as units and even believe
we _see_ as units _all_ groups of adjacent sensations which are more
or less homogeneously colored and sufficiently different from their
surroundings. So we must not be astonished by the fact that, in the
mist for instance, an area of darker nuance is seen as one individual
something, though we may be unable to tell its _special_ use or meaning.
I am not satisfied, however, by this form of the theory either. Units
are formed and segregated in the field in a great many cases where
this rather bold explanation does not apply. Take all units consisting
of separate parts! If we look up at the sky on a clear night, some
constellations of stars are seen immediately as belonging together
and as detached from their environment. Cassiopeia is an example, the
Dipper is another. In past ages people saw the same groups as belonging
together and at the present time children do not need instruction in
order to perceive them as units. In Fig. 1 the reader has before him
two definite groups of patches. Why not merely six patches? Or two
other groups? Or three groups of two members each? Looking passively
at the figure every one beholds those particular groups in the field,
two units being segregated, each containing three definite patches.
What about generalized meaning in these cases? No previous experience
could separate Cassiopeia from the other fixed stars around it. As far
as everyday experience goes, they all move together. And no hint at the
generalizing properties of memory will help here. We cannot possibly
assert that we have _learnt_ to see a number of separate patches,
similar to each other and different from the environment, as one thing
or one group, because they move together regularly. They are very far
from doing that. On the desk in my room are sitting five flies which
are five black dots as I see them from where I am. These dots begin
to move separately and to move in different directions. So do three
yellow leaves which a breeze lifts from the ground separately; so again
three stones which my hand moves, one after the other. My general
experience is that, at least as often as not, similar members of a
group, which are separated by the common background, are movable and
move _independently_. If, nevertheless, in this case definite groups
are formed and segregated, this happens despite our general previous
knowledge about the behavior of their members.
[Illustration: Fig. 1]
Investigating _which_ separate “patches” tend to become included in one
group, we find that, among other factors, their equality or similarity
and their common difference from other “patches,” favor their becoming
grouped together and their segregation from others. So we see that in
the case of separate members the same rule holds, without the influence
of meaning, which was said to explain unknown _continuous_ wholes
under the influence of generalized previous knowledge (cf. p. 153).
Consequently, in this latter case, the indirect genesis of groupings
through previous experience is not needed any more than it is where
separate members form groups. The grouping of separate members is
used in one of our tests for color-blindness: A rectangular field is
filled with dots at equal distances from each other. For the normal eye
certain groups of them belong together and are seen segregated from
the rest at once, and since these groups form written numbers, normal
persons will read the numbers without difficulty. The dots in question
have similar chroma and are sufficiently different from the others to
appear as one group which, as a whole, is recognized immediately. But
for those color-blind people who do not perceive the given differences
of chroma, no group will be segregated spontaneously, so that they
do not see and cannot read the numbers. In this example, the general
acquaintance with numbers is the same for both normal and color-blind
subjects. Therefore, the striking difference as to grouping depends
directly upon sensory conditions.
Groups consisting of separate members have a special interest for
theory insofar as they also prove that one unit segregated in the field
may at the same time belong to a larger unit. One dot in our last
example represents a continuous detached area; still it is a member of
a larger whole, the number, which as a larger unit is again segregated
in the whole field. There is nothing peculiar or mystical in such a
subordination, since, in physics, a molecule as a larger functional
whole contains several atoms as subordinate wholes. The atoms belong
to the molecule functionally; still they do not altogether lose their
functional individuality in that dynamical whole.
Following the casual observations of others, Wertheimer was the
first to see the fundamental importance of spontaneous grouping in
sensory fields and to demonstrate, by a great many examples, the main
principles upon which it depends. Most of his illustrations entail
the grouping of separate dots or lines, because, by using meaningless
constellations in this manner, it is easier to guard the demonstration
against disturbing arguments and criticism in terms of previous
knowledge. He has pointed out most clearly, however, that the same
principles may hold for all formation and segregation of wholes. I
do not know a better introduction to these problems than is given by
Wertheimer’s paper of 1923.[26] The reader is asked to make himself
acquainted with them by studying it. Some of the principles are easy
to understand. We have already considered one of them, which claims
that the equal and the similar tend to form units separated from what
is dissimilar to them. Where we have no differences of quality, or
other properties, among the members, relative distance will often be
decisive. In one of our examples _two_ groups (of three members each)
are formed, because among the six patches some distances are small as
compared with others, those patches, the distances separating which
are relatively small, belonging together in one group. In some cases,
perhaps the most interesting ones, it seems more natural to define the
rule of grouping not by given conditions, but by the tendency toward
certain results. As the physicist is accustomed to say that surface
tension works in the line of reduction of surface, so in the sensory
field grouping will produce certain wholes rather than others. We may
say that simple and regular wholes, or closed areas, are formed more
easily and more generally than irregular, or “broken,” and open wholes.
It becomes evident here that, in contrast to the indifferent mosaic
of sensations assumed in older theory, this order of the field shows
a strong “predilection” for certain general kinds of organization
as against others, exactly as the formation of molecules and the
working of surface forces in physics operates in certain definite
directions.[27]
Recently the nature of grouping as a sensory and elementary fact has
been demonstrated in the most convincing manner by experiments which
Hertz has made on birds (_Garrulus glandarius_).[28] A number of little
flower-pots are put upon the ground upside down. If the rather tame
bird, sitting high up on a branch, sees that the experimenter puts
some food under one of the pots, he will come down very soon, lift the
pot and take the food. This is a simple form of “delayed reaction” as
Hunter investigated it years ago. In these experiments, however, the
main point was not the _delay_ of reaction as such, but its dependence
upon the actual constitution of the field. The bird reacts without
difficulty if there is one pot only. But when there is more than one
everything depends upon whether the “right” pot in some way stands
out from the rest in the aggregate. If it is put in a regular line
with the others so that, for human vision, it becomes absorbed as one
indifferent member in a series, the bird lifts one pot or another
in a haphazard way, even if the distances between them are as large
as 25 cm. As soon, however, as, by grouping, the right pot becomes
something strikingly apart, i.e., segregated from the rest for the
human observer, the bird selects the right object at once. So in the
case of Fig. 2, in which the right pot is physically only 10 cm. apart
from a straight line of other pots, it is chosen at once. Obviously,
here, the line of other pots is a well-bound whole and the one pot a
segregated thing by itself for the bird as it is for man. Even in the
situation of Fig. 3, where the right object is 6 cm. from the next
and this 2 cm. from the last, grouping is definite enough to allow an
accurate reaction. But in the case of Fig. 4, where the right object
is 3 cm. apart from the next and this 2 cm. from the last, reactions
become a matter of chance. The bird cannot keep the right pot apart
before reacting, unless definite grouping helps him to do so. If the
grouping is very well determined for man, however, the bird will have
no difficulties at all, though the right object may be in immediate
contact with its next neighbor. In the situation of Fig. 5, 12 pots
are arranged so that they form a closed ellipse for human vision. The
right pot is put close to one of the other twelve. The human observer
will have before him one closed whole and one object outside. The bird
chooses the right one at once. This example seems to me particularly
valuable, because it shows that single objective distances as such are
not decisive, but rather the grouping which results from the _total_
constellation. How Hertz was able to demonstrate similar effects by
the application of other principles, as, for instance, differences
in size or chroma, may be better appreciated by reading the original
paper. To me these experiments seem to open an altogether new field
of research in animal psychology, providing we give up our somewhat
conservative and negativistic mood in this branch of science, and begin
to believe in the possibility of new problems. But as that negativism
has not yet disappeared completely, I should remark that, if grouping
is demonstrated in these birds as a “sensory fact,” it does not imply
“consciousness” in the animals. From our viewpoint, it is true, this
does not matter very much (cf. above Chapter II). One thing is proved,
however, that grouping occurs in sensory processes.
[Illustration: Fig. 2]
[Illustration: Fig. 3]
[Illustration: Fig. 4]
[Illustration: Fig. 5]
By further experimentation it must be possible to find out how far
birds and other animals see _continuous_ wholes, segregated in the
field, as man does; though even now it would be difficult to understand
the behavior of those birds, and their reactions to grouping, if the
pots themselves were not detached units in their field. In any case
the elementary nature of continuous wholes is demonstrated by certain
observations on the first reactions of congenitally blind persons after
they have been operated upon. Generally, the problems most interesting
to the ophthalmologist in those cases are those of visual depth and
of an original similarity between forms in vision and forms in touch.
Results have been discussed in several ways, but in most of the cases
one side of the observed facts is not given adequate attention. It is
generally true that when the patient is asked about an object, known by
touch from previous life, but given him the first time optically and
without the help of touch, there is no satisfactory answer; with a very
few exceptions the patient does not recognize those forms directly.
Still there is something very positive in his reactions: When asked
about “that something” which he has before him, _he understands the
question_. Obviously he has before him some thing as a segregated
unit, to which he refers the question and which he tries to name. At
least, if the object is a simple and compact form, the patient does not
have to _learn_ what “aggregate of sensations” he shall “treat as one
thing.” Thus elementary organization is an original sensory fact.
In Wertheimer’s paper on sensory grouping one finds the same problem
discussed in the case of wholes of a somewhat different sort. As
we experience _time_, it has some properties in common with space,
particularly with one dimension of it, namely its sagittal axis with
man as the center. Therefore, words referring to relations on this
axis are used as terms for temporal relations everywhere and in all
languages. In English we have something “before” or “behind” us in both
meanings; we look “forward” in space as in time, and death will come
“nearer” in time, as one place is nearer to me in space than another.
Perhaps, physiologically, there is a corresponding similarity between
the two, because, with respect to the organization and segregation
of extended units, we find the same general principles determining
temporal order which are known to us from the visual field in a state
of rest. By approaching my hand now and then for two-second intervals
to the opening of an organ pipe which is sounding continually, I can
lower the pitch slightly. In hearing, the effect will be a segregation
of the corresponding number of auditory units, the constant tone
appearing as general background and the somewhat different notes as
so many “patches” singled out from it. Of course, there are no such
units in the physical stimulation. Physically we have thousands of
waves of equal or different wave-length, all of them following each
other indifferently. It hardly needs to be mentioned that in the same
manner an appropriate succession of visual stimuli will be found to
result in temporal unification and segregation. The same thing is true
of touch and other senses. Again, “temporal dots” will readily form
“temporal groups” in all these cases, the groups containing the dots as
subordinate units and so forth.
It is in these _groups_ that the principles of temporal organization
are recognized most easily. With my finger I tap on the desk three
times at very short intervals and, after waiting for a second, I
repeat the tapping. People who hear this sequence for a while get
groups in time. Physically each sound is indifferent to every other;
they are independent events as the stars of Cassiopeia are practically
independent. Logically, other forms of grouping are quite possible
which do not occur, however, in the experience of an observer who
is listening calmly. Therefore, the groups, as we observe them,
represent an example of physiological or, if one likes, psychological
organization. The principle determining it in this case is relative
distance in time exactly as relative distance in space was a principle
of grouping in the simultaneously presented visual field. If all
the intervals are made equal, we still get groups when introducing
differences of intensity or quality in the series, especially when
the tapping is done according to a simple regular scheme. In temporal
sequences equality or similarity plays the same rôle as against
differences of properties, which we have found in the visual field.
[Illustration: Fig. 6]
In the most general case of sensory organization both space and time
are involved in the same experience of grouping. A simple example will
show what is meant: In a dark room we move a lamp hidden in a box, so
that one bright point is the only thing visible on the dark ground.
Let us suppose that the point moves in the following form without a
change in speed: _vide_ Fig. 6. A naïve observer will describe what he
has seen as three curious figures, or three movements (I, II, III);
perhaps he will correct himself after a while and say that there were
seven movements (1, I, 2, II, 3, III, 4). But he will not say that he
saw 53 or 16 or 29 movements! Now, as applied to the number of optical
stimuli which impinge serially upon his retinæ as quite independent
events, there is no reason why one of the larger numbers should be
less correct than three or seven. But, in experience, instead of an
indifferent series we again find a definite product of organization.
The reader will have realized already that with respect to a more
complex experience such as I may have if I see some one “nodding twice”
or “shaking his head a few times,” there is much in the experience
that is not covered by our present discussion; but, neglecting the
meaning of those particular movements, he will also realize that there
is a sensory organization of the given movements into “two” or “a few”
sub-wholes.
This seems to be an appropriate place to mention an indirect
explanation of organization and grouping, preferred by some of the
best psychologists in America. If I understand them rightly, a few
of them claim that the overt movements which we make when responding
to stimuli will produce the facts in question. Others would say that
one particular kind of experience, namely, the kinesthesis occurring
during such movements, is responsible for organization and grouping. In
order to answer certain obvious objections, the first will say that in
adults mere _tendencies_ to movement will suffice instead of the overt
movements which occurred originally. Similarly, the other hypothesis
assumes that even faint reproductions of past kinesthetic experiences
will be sufficient to explain organization of other (e.g., visual)
experiences in the adult.