Page:Mind (Old Series) Volume 11.djvu/74

THE TIME IT TAKES TO SEE AND NAME OBJECTS. By JAMES McKEEN CATTELL. The relation of the sensation to the stimulus and the time taken up by mental processes are the two subjects in which the best results have been reached by experimental psychology. These results are important enough to prove those to be wrong who with Kant hold that psychology can never become an exact science. It would perhaps be convenient to call the work done by Weber, Fechner and their followers in determining the relation of the sensation to the stimulus Psychophysics, and to confine the term Psychometry to the work done by Wundt and others in measuring the rapidity of mental processes. Psycho- metry seems to be of as great psychological interest as Psycho- physics, but it has not been nearly so fully and carefully worked over. This is partly due to the difficulties which lie in the way of determining the time taken up by mental processes. Such a time cannot be directly measured ; the experimenter can only de- termine the period passing between an external event exciting mental processes and a motion made after the mental processes have been completed. It is difficult or impossible to analyse this period, to give the time required for the purely physiological operations, and to decide what mental processes have taken place, and how much time is to be allotted to each. Experi- menters have also met with two other difficulties. The physical apparatus used seldom produces the stimulus in a satisfactory manner or measures the times with entire accuracy, and must be so delicate and complicated that it requires the greatest care to operate with it and keep it in order. The other difficulty lies in the fact that the times measured are artificial, not corresponding to the times taken up by mental processes in our ordinary life. The conditions of the experiments place the subject in an ab- normal condition, especially as to fatigue, attention and practice, and the method has often been such that the times given are too short, because the entire mental process has not been measured, or too long, because some other factor has been in- cluded in the time recorded. Considering therefore the difficulty of analysing the period measured, the inaccuracies of the record- ing apparatus, and the artificial and often incorrect methods of making the experiments, we have reason to fear that the results obtained by the psychologist in his laboratory do not always give the time it takes a man to perceive, to will and to think. Wundt has done much toward obviating these difficulties, care- fully analysing the various operations, and improving the ap- paratus and methods. It has seemed to me, however, worth the while to make a series of experiments altogether doing away with involved methods and complicated apparatus, and looking to