Licence: In copyright
Credit: The mind of man : a text-book of psychology / by Gustav Spiller. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![Fechner {Revision, 1882, p. 146) thus defines Weber’s celebrated law dealing with intensities. “ The sensory difference for two stimuli does not alter when the stimuli, on a change in their absolute magnitude, retain the same relation to one another, that is to •say, when the relative difference between the stimuli remains unaffected.” (2) The quality of a sensation is more evident. * Blue is different from red and red is different from green. The difficulty arises when we wish to determine the limits of qualities, and for this reason it would perhaps be safest to say that every appreciable , sense-change is a change in sense-quality. Thus two reds which impressed i us alike would be the same in quality j while absence of identity would t; imply difference in quality. j It is not easy to discover sharp divisions in the qualities. If a certain k shade of bright scarlet and a certain shade of dark green were the only two ^ shades known to us, we should have two defined colour qualities j but this I is far from being the case. The sea at which I was looking yesterday, |p showed, if I mistake not, distinct traces of all shades of grey—from white to nearly black, all shades of green, all shades of blue—from greenish blue I: to purple, all shades of yellow, and traces of red in the purple. And these I' variations melted one into the other.f What is true of the colour sense, ■•seems generally true of each of the higher senses. [Tesi] I The graver question now arises as to whether one sense shades into the l^; other, whether, for instance, hearing shades into seeing. We have learnt I-already in this section that the inferior senses apparently do so. If I now iigradually lower the eyelids till they are almost closed and look at an |i inverted picture, I notice the following. [Experiment] Through loss in ^detail the sense of depth is entirely gone, and from the same cause, things ^lare located nowhere, or, as we should say, in the eye. The blur which [^excludes colours, forms and spatial relations, suggests something felt jrrather than seen. At all events, this blur seems to me distinctly of the ('nature of a confused feeling, almost void of all optical suggestion, certainly ffree from shapes or lines. In this manner it is possible that we may bridge ;the widest gulf between the senses. Again, a low hum, when it is a :question of the sense of hearing, is equally suggestive of feelings like : touches or temperatures. J (3) The nature of feeling tone or sense-feeling, is amply discussed in :ch. 6. (4) According to Prof. Ward and others the feeling of extensity is the :basis of extension. Thus he reasons that if we paste one postage stamp 30n the back of the hand and then one next to it, we obtain a sense of .difference which lies at the basis of the sense of extension. [Test] I ihave tried the experiment, but with most disappointing effect, for the sensa- .tions themselves gave no notion of the space covered; strictly speaking, dndeed, they did not tell that any space was covered. The sensation was As to the nature of quality, see Sully, Human Mind, 1892, i, pp. 90-4. t Magnus, Die Entwickelung des Farbensinnes, 1877. + For a fuller discussion, see sec. 189.](https://iiif.wellcomecollection.org/image/b21938982_0073.jp2/full/800%2C/0/default.jpg)
