THERE is a very common prejudice respecting the rapidity of thought, which is imagined by many to be almost unlimited: and the opinion is very worthily illustrated by a reference to the oriental tale of a man’s being bewitched into the belief that he had passed through a period of seven years duration, and full of the most striking vicissitudes; all in the time that he employed in dipping his head in a pail of water. Now there is no doubt that we often dream of a period of many years while we are only sleeping an hour; that is, we dream of an impression of a long continued existence, or perhaps of some detached fact scattered through such a period: but if any person will write down all that he can possibly recollect, of the separate imaginations that have passed through his mind in the dream, he will find that he will be able to read them over with ease in less than five minutes.
It is probable that there may be considerable diversity in the rapidity of thought in different persons, as there is in that of muscular motions: but there is no reason to think the diversity greater. A healthy young man can run a mile in five minutes: a good pedestrian in four; but no man ever ran a mile in three minutes; and perhaps no horse in two. There is reason to think the rapidity of thought does not differ more materially than this in different individuals.
The rapidity of thought seems, however, more intimately connected with that of muscular motion than by analogy only: for they appear in some cases to be absolutely identical.
I have often been able to count ten in a second, in audible English words; not distinctly, indeed, but so as to assure myself that I do hear the ten words in their proper order; and to repeat the sounds for several consecutive seconds. If I say the words to myself only, that is, if I think them over, I cannot repeat them ten times in less than about nine seconds: I can never, for example, keep pace with my pulse, though it sometimes beats as slowly as seventy in a minute: nor can I, by any effort, think over the numbers from one to twenty in two seconds.
If I say to myself the first lines of Milton or Virgil, or [p309] Homer, or any other lines that may be still more familiar to me, I cannot get through them much, if at all, more rapidly than I can pronounce them, even when I fix my undivided attention on them.
The rapidity of sensation is also intimately connected with that of memory and of muscular action. To cast the eye over a sentence, attending to every letter, is an operation which is capable of equal rapidity with the saying it over mentally: but it cannot be made much more rapid. It required four seconds to look over a sentence which occupied six in rapid reading.
The operations, which succeed each other with this limited rapidity, are not incompatible with a partial attention to other subjects: just as in running or walking, we may have our feelings very strongly interested by the sight of surrounding objects without interrupting the train of voluntary motions, which seems thus to be so linked together in a continued chain, as to become almost involuntary. And we may certainly be saying a thing over as rapidly as possible to ourselves, and may at the same time be seeing, and hearing, and even reasoning, so as to keep up what amounts very nearly, though not completely, to a continuity of attention to several distinct trains of ideas: in the same manner as the nerves of involuntary action are notoriously employed in several distinct trains of concatenated muscular motions and vascular actions, and as the ear of a musician is able to follow and retain a dozen different melodies in harmony with each other at the same time.
Dr. Darwin mentions an experiment which has a similar tendency to show the close connexion between thought and sensation. He says, that if we think intensely of a deep colour, for instance red, with the eyes closed, we shall see a tinge when we open them of the opposite colour, or green; just as if we had actually looked at a red colour instead of thinking of it. But I confess that I have never been able to satisfy myself completely of the success of the experiment.
These very hasty observations appear to me to be in great measure original; and the results of such experiments are certainly more calculated to illustrate the nature and powers of the human mind, than the fanciful hypothesis of the fashionable [p310] craniologists, with all their measurements of the heads of murderers, are likely to become.
ZMINIS.