THE ORGANIZATION OF THE TASTES
_System and Organization in Other Senses_
IN the case of some of the sensory modes it is possible to arrange the
various elementary qualities in a schema or graph, representing in a
diagrammatic way their relations to each other, the results of their
combination, their influence on each other, etc.
Thus, in the case of vision the conventional “color pyramid” expresses
the various relations between the different elementary colors and the
different degrees of brightness. Red, yellow, green, and blue occupy the
corners of the base of a double pyramid. The upper apex represents white
and the lower apex black. On the side between red and yellow are found
the various oranges which result from mixing red and yellow light in
varying proportions. On the remaining sides are represented the
combinations of yellow and green, green and blue, blue and red. Along
the vertical axis range the different grays. Cross sections of the
pyramid indicate, at different levels, the result of mixing the
different colors with these grays, thus yielding the tints and shades of
the colors. Along the base, the colors which are at the extreme ends of
any diagonal passing through the center are complementary,—they
neutralize each other when mixed and under other circumstances each
tends to induce the other by contrast. The visual manifold may thus be
adequately schematized on a three-dimensional figure.
In a similar way the various tones, in the case of hearing, may be
arranged along a one-dimensional line, which represents the tonal scale.
Is it possible to arrange in any such systematic way the elementary
taste qualities so as to indicate their relationship to each other?
Before suggesting such a diagram it will be well to have in mind just
what relationships the various taste qualities do as a matter of fact
display.
_Taste Mixtures and Compounds_
The testimony of daily experience would probably be at once that the
various elementary tastes may combine to produce new tastes of a more
complex or even of a unitary character. Thus, the taste of lemonade is
distinctive enough. Yet even casual observation suffices to show that
the sweet and the sour components have by no means lost their identity,
since each can be singled out in attention and recognized as the
familiar elementary quality. Red and blue may fuse to produce a violet
or a purple from which the original elements can by no means be singled
out and identified through direct inspection. But it seems to be the
rule that tastes do not behave in this way, although the demands of
daily experience do not readily lead us to discover the fact. “Think,
for instance,” writes Titchener, “of the flavor of a ripe peach. The
ethereal odor may be ruled out by holding the nose. The taste
components,—sweet, bitter, sour,—may be identified by special direction
of the attention upon them. The touch components—the softness and
stringiness of the pulp, the puckery feel of the sour—may be singled out
in the same way. Nevertheless, all these factors blend together so
intimately that it Is hard to give up one’s belief in a peculiar and
unanalyzable peach flavor. Indeed, some psychologists assert that this
resultant flavor exists; that in all such cases the concurrence of the
taste qualities gives rise to a new basic or fundamental taste, which
serves, so to say, as background to the separate components. There is,
however, no need to make any such assumption. It is a universal rule in
psychology that when sense qualities combine to form what is called a
perception, the result of their combination is not a sum but a system,
not a patchwork but a pattern.... Hence, just as it would be absurd to
say that the plan of the locomotive is a new bit of steel or the pattern
of the carpet a new bit of colored stuff, so is it wrong to say that the
peach character of a certain taste blend is a new taste quality.”
The mixture of stimuli provoking two taste qualities does not, then,
produce intermediate qualities such as the orange which results from the
mixture of red and yellow. Instead, in this case, the two qualities do
one of these three things: (a) they may remain separate and distinct;
(b) they may fluctuate individually and alternate with each other in
their appearance; (c) they may tend to neutralize each other. If the
stimuli are very intense, oscillation is the common result. If the
stimuli are weak, some degree of neutralization is reported to be the
rule. Only in one case, namely, the mixture of sweet and salt, does a
new taste seem to emerge, which does not resemble either of the original
qualities. Kiesow finds that such a mixture, in the case of weak
solutions, gives rise to a quality described as “flat,” “vapid,” or
“insipid,”—the alkaline taste which we have already considered.
_Compensation, Antagonism, and Neutralization_
In the case of color, there may be found for every quality or mixture an
opposite quality or mixture which when combined with the former either
completely neutralizes it or at least reduces its intensity. Thus blue
and yellow, of the proper tones and proportion, cancel each other,
leaving only an experience of gray. So do a certain olive color and a
particular violet, a certain orange and a particular bluish-green, a
certain red and a particular green.
We have already suggested that in case of weak taste qualities a similar
effect is present. “With the low intensities there is in most cases a
partial compensation, which is least for sweet and sour, better for salt
and bitter, better still for sour and bitter, sour and salt, sweet and
bitter.” These facts are utilized in daily life in the countless
combinations of dressings, sauces, seasonings and condiments used in the
preparation of food. We take sugar with our tea, our coffee, our
chocolate, our strawberries, our grapefruit, and our lemon juice, and
realize that it to some degree counteracts or neutralizes the bitter or
the sour taste of these foods in their original form. “Salt corrects the
sweetness of an over-ripe melon.” In our salad dressings, sauces,
gravies, relishes, and bitters we find the means of reënforcing or
toning down the taste qualities to suit our own particular fancy.
In part, of course, these effects are not achieved through the mere
process of neutralization. The addition of touch qualities, such as the
pucker of vinegar, the sting of pepper, the bite of mustard, and the
burn of onion, plays its own part in the constitution of a flavor,
regardless of their compensating influence on the pure taste qualities.
In line with the fact that taste and odor are easily confused, and
contributing perhaps to this confusion, is the fact that tastes and
odors are related to each other through their antagonism, almost if not
quite as definitely as are the qualities within each of the separate
modes. Thus, the sickening odor of many medicines is somewhat palliated
if they are taken in fermented juices or with the sour acids of fresh
fruits. “Quinine, which tastes bitter and has no smell, is corrected by
essence of orange peel, which has an aromatic smell and no taste.”
Titchener pertinently remarks that these results may in part arise from
the simple process of distracting attention from an unpleasant item to a
more agreeable part of the experience. On the other hand, the special
effectiveness of the introduction of odors into the complex rather than
pleasant sights and sounds suggests that the results in the case of
taste and smell are not solely a matter of attention, but are in part,
at least, dependent on the essential relationships between the qualities
of these two modes of sensation. In the chapter on “The Evolution of
Taste” certain light is thrown on the closeness of these relationships
by our knowledge of the intimate biological connection between taste and
smell. In certain lower forms of animal life it is indeed quite
impossible to draw any clear line between these two features of “the
chemical sense.”
In general, then, although the facts of compensation, antagonism, and
complementariness are to be observed within the field of the taste
qualities, the relations disclosed are by no means as definite nor as
systematic as they are in the case of vision. For a given primary color
quality there exists only one other elementary quality which stands to
it in the relation of antagonist. But we have seen that in the cases of
both sour and bitter there is at least some degree of antagonism with
all three of the other qualities, while both sweet and salt antagonize
in some degree both sour and bitter. Moreover, at least the sour, the
bitter, and the sweet appear to show antagonistic relations to certain
qualities of smell.
In none of these cases has there been presented clear evidence showing
the ability of one quality to totally efface another, so that no taste
whatever is present. In the case of colors, however, the result of such
combinations in the right proportions may easily be a total absence of
color quality. It is true that occasional instances of such effects in
taste have been reported, but the general rule seems to be that the
extreme degree of neutralization leaves an experience which is
recognized as a taste, but which is described as “flat” or as “insipid.”
It is possible, of course, that this “insipid” taste quality is the
tactile and kinæsthetic residue of the total experience, much as the
“gray” which results from the combination of complementary colors may be
described as the brightness residue of the total momentary effect. But
in the latter case the residue would be distinctly “visual” although not
“color.” In the case of taste nothing corresponding to the “brightness”
of vision is recognized, and the residue as we have described it would
consequently belong to a different mode of sensation.
_Contrast Phenomena_
The phenomena known as contrast are very familiar sense experiences. Not
only is it true that in the fields of perception and feeling the tall,
the good, the wholesome, the fast, the daring, and the pleasant have
their qualities enhanced when they accompany or follow upon the
diminutive, the wicked, the foul, the slow, the cowardly, and the
disagreeable; in the case of more simple sense experiences also contrast
effects are often both immediate and striking. The apparent temperature
of the air or water varies with the conditions from which we emerge into
them. The sudden calm after a thunderstorm seems even more empty than
the same conditions in Indian summer. The palest complexion assumes a
moderate rosiness if green ribbons and fabrics are suitably arranged
about or near it. Even a pure gray strip of paper becomes a rich pink
line or a yellowish band when placed across a background of saturated
green or blue.
Daily experience entails many such instances of contrast in the case of
the taste qualities as well. A ripe apple may surprise us by its
unexpected sourness if we come to it direct from a box of bonbons.
Experiments designed to investigate the presence and character of taste
contrasts are especially interesting and their results are in many ways
curious. If, under proper experimental precautions, a salt solution is
applied to one side of the tongue and a drop of tasteless distilled
water is simultaneously applied to the other side, the tasteless water
is reported as sweetish. If, instead of the distilled water, one apply a
sugar solution of such weakness that its taste could not under ordinary
circumstances be recognized, the sweetness becomes clearly apparent.
Under the same circumstances a solution otherwise producing a weak
sensation of sweetness is reported as being “very sweet.” The salt
solution, that is to say, induces by contrast the quality of sweetness
in tasteless substances and enhances the degree of an otherwise weak
quality aroused at another region of the tongue.
In much the same way a sugar solution induces saltiness, or sourness, or
perhaps bitterness, according to the individual, the occasion, and the
circumstances. Sometimes the salt induces a sour instead of the sweet.
The bitter, however, seems unable to induce other qualities by contrast,
and is at least seldom induced by the other qualities.
In this as in other respects the bitter quality seems to show
idiosyncrasies. Thus, it is generally accepted that no papillæ are ever
sensitive only to bitter stimuli. Many primitive languages are said to
contain in their vocabulary no word for bitter: it is not uncommon in
daily experience to find bitter confused with sour; bitter seems to be
especially easily antagonized by certain odors; it does not display
striking contrast phenomena; and its reaction time is exceptionally
slow.
The type of contrast which we have thus described in the case of the
tastes is known as _simultaneous contrast_. Both stimuli are applied at
the same time to different parts of the sense organ. What is known as
_successive_ contrast can also be experimentally produced. Here one of
the stimuli follows the other after an interval in which nothing is
applied or, still better, in which the mouth is carefully rinsed with
water. This is the type of taste contrast with which we are most
familiar in daily life. The same contrasts may be induced experimentally
by this method as result from the simultaneous method. But the inducing
stimuli in this case must be rather more intense than is necessary for
the production of simultaneous contrasts. In much the same way in
perception as in sensation the contrast between two extremes or
opposites is better realized when both are present together than when
one follows the other after an interval.
The general facts of taste contrast are succinctly summarized by
Titchener in the following way:
(1) Salt and sour contrast: the sour induced by salt being clearer and
stronger than the salt induced by sour.
(2) Sweet and sour contrast: the sweet induced by sour being clearer and
stronger than the sour induced by sweet.
(3) Salt and sweet contrast: the sweet induced by salt being clearer and
stronger than the salt induced by sweet.
(4) Bitter shows no contrast at all.
(5) The order of qualities, as regards ease of induction, is sweet,
sour, salt, bitter.
_After Images of Taste_
Suggested by the phenomena of contrast are the somewhat related facts of
after sensations or after images, as they are sometimes called. When one
looks for a moment at a candle or other source of light and then quickly
extinguishes it or looks away from it, one still continues to see, for a
time, a luminous form, which may persist for a considerable time after
the removal of the stimulus. In such a case the color and brightness of
this after image may be the same as those of the original object, and
the after image is hence said to be _positive_. Under certain conditions
the colors of the after image are complementary to those of the original
and the brightness relations of the various parts are reversed. The
after image is then said to be _negative_. Or if after looking at a
colored object one transfers his gaze to a gray expanse there appears
upon this gray field an outline of the original object, with colors
which are complementary or antagonistic to those of the original. After
sensations of pressure arising under special conditions have been
described, and positive after effects of warm and cold stimuli seem also
to be demonstrable. Even after sensations of sound, somewhat weak,
transitory, and by no means easily detected, have been described. In all
these cases except vision the after sensations are of the positive type
only.
In the case of taste, and of smell also, it is difficult to investigate
the presence of such after sensations, inasmuch as it is by no means
easy to be sure that some trace of the stimulus does not remain in or
near the sense organ. An experience reported as a positive after
sensation might easily enough represent only the effect of persistent
stimulation by these traces of the substance. At least one investigator
is convinced that in his observations of taste experiences “the
sensation continued after the tongue was so carefully dried off that no
particles of the tastable substance were left.” Similarly, experiences
of tastes being “left in the mouth” are very common. But our inadequate
control over the disposition of the sapid substance and the complicated
chemical relation which exists between various substances and between
some substances and the natural juices secreted in the vicinity of the
taste organ makes it impossible to assert with certainty either the
presence or the absence of after sensations of taste.
_The Schema of Taste Relations_
The foregoing facts concerning the phenomena of mixture, fusion,
antagonism, contrast, and after sensation show at once the
impossibility, in our present state of knowledge, of arranging the taste
qualities in any such systematic scheme as is represented by the color
pyramid and the tonal scale in the cases of vision and hearing. It by no
means follows, however, that such orderly arrangements have not been
attempted.
[Illustration: Fig. 1.]
Kiesow, one of the most famous students of the sense of taste, proposed
that a circle with a vertical and a horizontal diameter indicated would
best represent the various relations between the taste qualities. At top
and bottom would stand salt and sweet; to left and right, bitter and
sour. Along the horizontal diameter would be placed the mixtures of
bitter and sour, and along the vertical diameter would range the various
results of mixing salt and sweet. The mixtures of salt-sour, sweet-sour,
bitter-sweet, and bitter-salt would stand in their appropriate places
about the circumference or periphery of the circle.
Wundt tentatively adopts a similar scheme when he says: “The system of
taste sensations is, accordingly, in all probability to be regarded as a
_two-dimensional_ continuity, which may be geometrically represented by
a rectangular surface at the angles of which the four primary qualities
are placed, the various mixed qualities being placed along the side and
on the inner surface.”
To such suggestions, however, Kuelpe objects that: “There is no
indication of a continuous transition between the four qualities which
tastes appear to present, as there is between the qualities of tone
sensations. They form, not a one-dimensional manifold, but a discrete
system of unknown relations.”
Titchener, one of the most careful students of sense experience, is less
emphatic, but he “doubts whether, in the present state of our knowledge,
this idea (that of Wundt) can be accepted.” He doubts “whether the
sweet-sour of lemonade stands to its originals as blue-green stands to
blue and green, or as orange to red and yellow; and also whether bitter
should lie in the same plane with the other three taste qualities. We
must suspend judgment; in the meantime, Kiesow’s figure provides us with
a working hypothesis.”
Ladd and Woodworth align themselves with Kuelpe and conclude that,
“there is no clear indication that the tastes can be arranged in a
linear scale, as the primary colors are, nor that any taste stands to
any other definitely in the relation of opposite or complementary. On
the whole it appears as if the four tastes were rather isolated from
each other, each representing almost an independent sense.”
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