Volume 1
A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers.
- Charles Samuel Myers
- Date:
- 1911
Licence: Public Domain Mark
Credit: A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers. Source: Wellcome Collection.
116/370 page 94
![of the retina, are the expression of activity in an altogether distinct apparatus. [Rollet has suggested, and in this country McDougall has independently elaborated, a theory of simultaneous contrast, in order to escape from the difficulties involved in Helmholtz’s explanation. This theory attributes simultaneous contrast to the inhibitory action of a given cortical visual process upon the visual processes in neighbouring cortical regions. If, for example, a grey surface be fixated which has a red square upon it, the cortical area excited by the red only differs in activity from that excited by the grey (according to Helm¬ holtz) in that the red apparatus is far more powerfully stimu¬ lated in the former. The theory, now introduced, supposes that the highly excited activity of this ‘ red area ’ depresses the activity of the red apparatus in the neighbouring ‘ grey area ’ of the cortex, whereby the blue and green in the latter area predominate over the red apparatus. McDougall sup¬ poses that such inhibition is due to a drainage of nervous energy from less active (or inactive) into more active regions,— a hypothesis which needs stronger physiological support before it can be accepted. We shall again mention it (Chap. XXV.) when we come to deal with the process of attention. It is owing to this supposed inhibition of the red that the contrast blue-green colour is produced.] Unsatisfactory as is the Young-Helmholtz theory in its original form, it must at the same time be admitted that Hering’s theory is by no means free from difficulties. There are many who find it inconceivable that a sensory experi¬ ence should be produced by assimilation changes in living substance. Even those who accept Hering’s views as to the elementary nature of the sensations yellow and white, and as to the relation of colourless and colour sensations under ordinary conditions of illumination, feel it impossible to reject von Kries’s theory of rod vision in the dark-adapted eye; they either discard Hering’s theory of the specific brightness of colours altogether, or consider it inadequate to account for the facts. Others, again, refuse on the following ground to place the](https://iiif.wellcomecollection.org/image/b3135984x_0001_0116.jp2/full/800%2C/0/default.jpg)
