Tactile sense

“ Moreover, as a matter of fact, it is certain that the muscular sense is so closely connected with both the visual and the tactile senses, that, by the ordinary laws of association, the ideas which it suggests must needs be common to both. ”

“ Furthermore, the stimulation of our tactile imagination awakens our consciousness of the importance of the tactile sense in our physical and mental functioning, and thus, again, by making us feel better provided for life than we were aware of being, gives us a heightened sense of capacity. And this brings us back once more to the statement that the chief business of the figure painter, as an artist, is to stimulate the tactile imagination. ”

“ Perception of form comes from the combination of two sensations, tactile and muscular, muscular sensations being sensations of movement. What we call in the blind the tactile sense is in reality more often the stereognostic sense. That is, they perceive by means of their hands the form of bodies. ”

“ We gain a field of vision from an ensemble of local signs, and, as concerns tactile sense, the same thing happens, the functions of the corpuscles of touch being like those of the cones and rods of the retina in sight. ”

“ For suppose, to begin with, as Berkeley did, that all perception of extensity is to be referred to the sense of touch. We may, indeed, if you will have it so, deny extension to the data of hearing, smell and taste; but we must at least explain the genesis of a visual space that corresponds to tactile space. It is alleged, indeed, that sight ends by becoming symbolic of touch, and that there is nothing more in the visual perception of the order of things in space than a suggestion of tactile perception. ”

“ Supposing the ultimate organs of the sense of touch to be really congregated more thickly under the ridges than under the furrows—on which there has been some question—the power of tactile discrimination would depend very much on the closeness of the ridges. ”

“ Tactile sensibility, too, must be carefully allowed for. The sense of varying resistance in the air may reach in some seeing persons, as well as in the blind, a high degree of acuteness. [177]
But there are cases of sudden motor inhibition where no warning can well have been received from hyperæsthetic sensation, where we come, as it seems, to telæsthesia or to spirit guardianship. ”

“ Helen Keller's brain, as shown by her accomplishments in later life, was a remarkable one; not long after birth she became deaf and blind, consequently there was practically only one avenue of intelligence left open for the education of that brain, viz. the tactile kinæsthetic. But the tactile motor sense is the active sense that waits upon and contributes to every other sense. The hand is the instrument of the mind and the agent of the will; consequently the tactile motor sense is intimately associated in its structural representation in the brain with every other sense. ”

“ The tip of the tongue possesses the most acute sensibility of any portion of the body, and next in order are the tips of the fingers. The hands are the principal organs of tactile sensation. The nerves of general sensibility are distributed to every part of the cutaneous tissue. The contact of a foreign body with the back, will produce a similar tactile sensation, as with the tips of the fingers. The sensation, however, will differ in degree because the back is supplied with a much smaller number of sensitive filaments ”

“ When to learn the form of an object we move the hand over it, muscular sensations are combined with proper tactile, and such a combination of the two sensations is frequent; moreover, we rarely touch anything without at the same time getting temperature sensations; therefore pure tactile feelings are rare. From an evolution point of view, touch is probably the first distinctly differentiated sensation, and this primary position it still largely holds in our mental life. ”

“ English idealism sought to reserve to tactile perception a monopoly of the extended, the other senses dealing with space only in so far as they remind us of the data of touch. A more attentive psychology reveals to us, on the contrary, and no doubt will hereafter reveal still more clearly, the need of regarding all sensations as primarily extensive, their extensity fading and disappearing before the higher intensity and usefulness of tactile, and also, no doubt, of visual, extensity. ”

“ This leads us to believe that what is seen is usually tangible, and that it has, whether we touch it or not, the hardness or softness which we should expect to feel if we touched it. But the mere fact that we are able to infer what our tactile sensations would be shows that it is not logically necessary to assume tactile qualities before they are felt. All that is really known is that the visual appearance in question, together with touch, will lead to certain sensations, which can necessarily be determined in terms of the visual appearance, since otherwise they could not be inferred from it. ”

“ For example, most of the visual objects in our neighbourhood rouse tactile images: we have a different feeling in looking at a sofa from what we have in looking at a block of marble, and the difference consists chiefly in different stimulation of our tactile imagination. ”

“ But this difference in the accessibility of phenomena is not due to their peculiar nature. It is connected with a different fact, with the modes of excitement which call them forth. If the visual sensation is common to all, it is because the exciting cause of the sensation is an object external to our nervous systems, and acting at a distance on all. [2] The tactile sensation is at the beginning more personal to the one who experiences it, since it requires contact ”

“ No part of the body except the point of the tongue is as sensible to touch as the tips of the fingers and the palm of the hand. Tactile discrimination is so acute as to be able to interpret to the brain significant impressions produced in very rapid succession. ”

“ Then with the consciousness of that mobility, the notion of space of three dimensions—which is "Raum" or "room" to move with perfect freedom—is at once given. But the notion that the tactile surface itself moves, cannot be given by touch alone, which is competent to testify only to the fact of change of place, not to its cause. The idea of the motion of the tactile surface could not, in fact, be attained, unless the idea of change of place were accompanied by some state of consciousness, which does not exist when the tactile surface is immoveable. ”

“ It is even conceivable, if not exactly likely, that certain operators may have learned to think directly, so far as the purely conscious part of the process of thought is concerned, in terms of the tick-auditory symbolism or, if they happen to have a strong natural bent toward motor symbolism, in terms of the correlated tactile-motor symbolism developed in the sending of telegraphic messages. ”

“ Obviously, there is no more likeness between the feel of a surface and the colour of it, than there is between its colour and its smell. All simple sensations, derived from different senses, are incommensurable with one another, and only gradations of their own intensity are comparable. And thus so far as the primary facts of sensation go, visual figure and tactile figure, visual magnitude and tactile magnitude, visual motion and tactile motion, are truly unlike, and have no common term. ”

“ On the other hand, consider tactile space, limiting ourselves to the sensations of a single finger, that is in sum the assemblage of positions this finger can occupy. This tactile space that we shall analyze in the following section and which consequently I ask permission not to consider further for the moment, this tactile space, I say, has three dimensions. Why has space properly so called as many dimensions as tactile space and more than simple visual space? It is because touch does not operate at a distance, while vision does operate at a distance. ”

“ More important still than the tactile sensations, properly speaking, are the sensations which pertain to what is sometimes called internal touch, deep-seated sensations emanating from all points of the organism and, more particularly, from the viscera. ”

“ Finally, before going on to our principal subject, we should glance at the instinctive chewing motions which were mentioned among tactile plays. When a full-grown man going for a walk sticks a twig in his mouth and gnaws it the movements of his own jaw are of more interest to him than is the stick, except as it promotes sensations of contact. ”

“ It is obvious on this scheme that the cell which we have marked K may stand for the seat of either a resident or a remote sensation occasioned by the motor discharge. It may indifferently be a tactile, a visual, or an auditory cell. The idea of how the arm feels when raised may cause it to rise; but no less may the idea of some sound which it makes in rising, or of some optical impression which it produces. Thus we see that the 'mental cue' may belong to either of various senses; and that what our diagrams lead us to infer is what really happens ”

“ We can identify it with a differently located tactile and visual image of 'the joint' itself.
Just so when we feel the tip of our cane against the ground. The peculiar sort of movement of the hand (impossible in one direction, but free in every other) which we experience when the tip touches 'the ground,' is a sign to us of the visual and tactile object which we already [Pg 42] know under that name. We think of 'the ground' as being there and giving us the sensation of this kind of movement. The sensation, we say, comes from the ground. The ground's place seems to be its place ”

“ True it is that in our visual and auditory sensations we do not, as in our tactile, directly cognosce the force which produces them; but the Physicist has no difficulty in making sensible to us, indirectly, the undulations by which sound is propagated, and in proving to our intellect that the force concerned in the transmission of light is really enormous. ”

“ The localizing power is a little more acute across the long axis of a limb than in it; and is better when the pressure is only strong enough to just cause a distinct tactile sensation than when it is more powerful ”

“ Repetition, and hence summation, intensifies and clarifies the{220} sensation of touch. As a consequence, whenever we want to test anything by touching it we do so repeatedly, drawing the finger up and down and holding the object between the fingers; for the same reason we repeatedly feel objects with pleasant exteriors. We like to move our hands up and down smooth or soft furry surfaces, in order to sense them more clearly, or to make the sensation different because of its duration and continuance. ”

“ In such a scheme, manual training must occupy a most prominent place, for it has to do with the most obvious forms of touch. I wonder if you ever reflected that our entire contact with the outer world, our entire knowledge of it, is in the last analysis dependent upon but one sense, the sense of touch, and that the sensory nerves, those telegraphic lines between our consciousness and the outer world, respond to but one operator, direct contact? ”

“ Whether touch be a sense delicate enough to discern such differences, would be, of course, a question for psycho-physics to decide,—and a question not simply of magnitudes, but of qualities of sensation. Perhaps it is not yet even legitimate to suppose that, just as by ear we can distinguish the qualitative differences of a million voices, so by touch we might be able to distinguish qualitative differences of surface scarcely less delicate. ”

“ But there is one effect which is not conjectural, and that is the sensation of touch. This effect, owing to physiological inference or perhaps to a reflex, is associated by us with the finger-tip. But the sensation is the same if, by artificial means, the parts of the nerve nearer the brain are suitably stimulated—e.g. if your hand has been amputated and the right nerves are skilfully manipulated. Thus our confidence that touch affords evidence of the existence of bodies at the place which we think is being touched is quite misplaced. As a rule we are right, but we can be wrong ”

“ We have said that no kind of our sensations—neither the visual, the tactile, nor the muscular—permits us to represent to ourselves the inmost structure of matter, because all sensations, without exception, are false, as copies of material objects. We are now assured that we are mistaken, and that our sensations are all true—that is to say, are faithful copies of the objects. If all are true, it comes to the same thing as if all are false. ”

“ This every one will admit. Must we not go further, and extend the admission to automatic actions which originally were voluntary, and have now lost all trace of ideal prevision, and almost all traces of accompanying consciousness? The motor mechanism has its symbols also; in this sense, that whereas the action which at first needed complex sensorial processes to set it going and keep it going, is now determined by a single one of those processes taking the place of their resultant. ”

“ For as they extend no farther than our arm's length, they correct the errors of other senses, which deal with distant objects, and scarcely grasp these objects at all, whereas all that the touch perceives it perceives thoroughly. Besides, if to nerve-force we add muscular action, we form a simultaneous impression, and judge of weight and solidity as well as of temperature, size, and shape. Thus touch, which of all our senses best informs us concerning impressions made upon us by external things, is the one oftenest used, and gives us most directly the knowledge necessary to our preservation. ”

“ When sight is the medium of perception movement plays are at the same time visual plays, otherwise consciousness is reached through the sense of touch. We will here give special attention to experimental exercise of the motor apparatus, as actual movement play is treated of in detail in another section. ”

“ We regarded the table-tilting process as in one sense the simplest, the least differentiated form of motor response. It is a kind of gesture merely, though a gesture implying knowledge of the alphabet. Let us see in what directions the movement of response becomes more specialised,—as gesture parts into pictorial art and articulate speech. We find, in fact, that a just similar divergence of impulses takes place in automatic response. On the one hand the motor impulse specialises itself into drawing ”