MIND'S TELEGRAPHY.

New Zealand Herald, Volume LIX, Issue 18170, 16 August 1922, Page 10

MIND'S TELEGRAPHY.

REACTION TIME PROBLEM.

VALUE OF EXPERIMENTS.

" Absence of body has a greater survival value than presence of mind," said Professor W. Anderson of the Auckland University College, in discussing the value of reaction time experiments in determining modern traffic control problems. The subject arose out of a recent prosecution iu the Supreme Court for manslaughter, in which the Crown alleged that the fact of the motor-cai concerned travelling 35yds. after the collision occurred was proof of exceusive speed. Mr. Justice Stringer demurred that no such inference could be drawn in the absence of evidence aa to the motorist's reaction time—it might take him an appreciable interval to apply the brakes after his mind had appreciated the fact of the collision.

The reaction time of an individual was defined bv Professor Anderson as the interval that elapsed oetweea the exhibition or application of a stimulus, such as a flash ot light orj a blow, and liis response in a preK-rititd manner. To get at the time of the pure or simple reaction, however, experiments had to be made to kolate it from the factors which complicated on everyday reactions. Such factors might be the study of the situation, deliberation as to what to do about it, or emotions connected with it. Simple reaction time was in every case a matter of a small fraction of a second. It was longer in the very young and tho very old and seemed also to have racial variations. The practical application of the principle to industry was limited to. operations of a very mechanical type, as in the well-known example of the discarding of defective <?toel balls for bicycle bearings. But coming to traffic problems reactions such as were important in the control'of vehicles iu.the Btreets were of a much more complicated nature, said the professor. Munstorberg, who studied tha capacities risquired of tram-drivers, found that what was required was rather the ability to pick out and evaluate the movements of the various components of the passing traffic, which was, at the first glance, simply a swarming mass shooting out particles in a highly-irregular manner. A ouick reaction-time waß, in Buch a case, while requisite, a comparatively unimportant factor. The effect of the emotions in delaying the normal reaction was well-marked. In extreme canes of surprise, for instance, the Biibiect stood " incapable of moving a limb, riveted to the spot, mouth open, eyes staring." Instances were recorded of railway servants and others being so affected by the approach of a train that they have been unable to save themselves by getting out of the way, though there was ample time to do so. One such man explained that he had no feeling of terror j he could not help watching the train as it darted toward him. His attention was so riveted that he was unable to make, or felt no desire to make, the appropriate movements. " I had to shake myself, and only did so just in time," he said. The principle of reaction time was used in the diagnosis of mental disturbances The last thing that the subject would, or could tell wag the source of his trouble. But if he were led to react to an apparently casual collection of words, by giving for each it« first associate in his mind, it would generally be found that a few words would stand out bv the longer time that he took to supply them. If these indications were carefully followed up, the cause of the trouble might be laid bare.