“TIME REACTIONS:” METHODS OF MEASURING THE TIME REQUIRED FOR PERFORMING VARIOUS MENTAL ACTS.

A sketch like this would be incomplete without a word about time reactions—a subject that historically was almost the first in the field, and has occupied more workers than any other. A generation ago “as quick as thought” was our extreme limit of expression. It outran “quicker than lightning.” The great physiologist, Johannes Müller, wrote, in 1844:

“We shall probably never secure the means of ascertaining the speed of nerve activities, because we lack the comparative distances from which the speed of a movement, in this respect analogous to light, could be calculated.”

We now know that sensory processes travel along the nerves on an average only about one hundred and ten feet per second, and often less than twenty-six feet. While you are performing the commonest judgment, electricity or light would have shot from continent to continent. The time-measurement of different mental processes is now one of the chief means which the psychologist uses for getting at mental laws. When certain measures are once determined, he uses these as the chemist does his familiar reagents, to dissolve the unfamiliar and more complicated combinations.

The following table shows in decimals of a second about the average length of time which our commonest judgments occupy:

SECONDS

To recognize the direction of a ray of light.011
To recognize a color when one of two, as red and blue, and expected to be seen.012
To recognize the direction of ordinary sounds.015
To localize mentally, when blindfolded, any place on our body, touched by another person.021
Mentally to judge a distance when seen.022
To recognize the direction of loud sounds.062
To recognize capital letters.180
To recognize short English words.214
To recognize pictures of objects.163
To add single figures.170
Given a month, to name its season.164 to .354
To answer such questions as “Who wrote Hamlet?”.900 and over.

406

Such then, are a few out of the many problems which have been experimented upon in the Harvard Laboratory during the last year—problems in perception, association, attention, “reaction times,” psycho-physic law, kinesthetics, esthetics, memory, will, and so on, covering nearly the whole range of mental phenomena. I have selected these few for presentation here, not for their importance over others, but because they could be simply described in these pages. The general aim of all the work is, however, very simple. As in the other sciences, it seeks to establish fact after fact, in orderly manner, along the whole line of mental nature; and by unifying these to work ever to a larger knowledge of the whole.

WAX SPECIMENS IN THE MUSEUM.