460 



SCIENCE. 



[Vol. VIII., No. 198^^ 



although in both cases the accuracy of the memory 

 was remarkably good.' When the tones were 

 really equal, they were recognized as such, on the 

 average, in from seventy-five to eighty per cent 

 of all cases. In using tones differing by only 4 or 

 8 vibrations, though the difference was very often 

 clearly perceived, the direction of it, whether 

 higher or lower, was not always clear, and even in 

 differences of 12 vibrations there was little confi- 

 dence in one's judgment. This seems to be a 

 peculiarity of auditory sensations: for in sight 

 you can almost as readily say that a shade is 

 lighter or darker than another as that it is differ- 

 ent ; you can almost as soon detect the dh-ection 

 in which a point is moving along the skin as you 

 can detect the motion itself. But the main point 

 is the effect of the time-interval between the tone 

 and its reproduction. This was varied from 1 

 second to 30 seconds, or even to 60 seconds, or 120 

 seconds in some experiments. The general result 

 is, that the longer the interval, the smaller the 

 chances that the tone will be recognized ; and this 

 process of forgetting takes place at first very 

 rapidly, and then more slowly. It is made prob- 

 able that the interval must increase in a geometri- 

 cal ratio to produce an arithmetical series of (ap- 

 proximately) equal degrees of forgetting ; i.e., the 

 curve is logarithmic. This law is subject to con- 

 siderable variations, one of which seems to be con- 

 stant and is peculiar ; namely, there seems to be a 

 rhythm in the memory itself, and, after falling, it 

 recovers slightly, and then fades out again. Among 

 other results were that the accuracy of the memo- 

 ry decreases as the , pitch of the tone is lowered 

 (within limits) ; that relatively high tones tend to 

 be judged too high, and low ones too low, by un- 

 musical ears ; that the effect of practice is at first 

 marked, but soon diminishes as is its general law ; 

 and that the recovering power of the ear is so 

 great that fatigue has little effect. To prove the 

 last proposition, experiments were made for one 

 day from 8 a.m. to 7 p.m. (with ten minutes inter- 

 mission). 



A subject that has always received great atten- 

 tion at the Leipzig laboratory is the measurement 

 of the time of psychic processes. These have 

 been conveniently divided into three kinds : 1°, 

 the reaction time, which is simply the time after 

 the application of the sense-stimulus necessary for 

 an individual to record the fact that he has re- 

 ceived the sensation ; 2°, the distinction or per 

 1 Very unfortunately, Mr. Wolfe, in tabulating his re- 

 sults, has worked upon a false mathematical process, and 

 has thus made it impossible to draw conclusions regarding 

 the recognition of the fine intervals of tone. From the 

 original records such conclusions could be drawn. I am 

 thus forced, on this account, to speak only of the recognition 

 of equality of tone, and even to make allowances in stating 

 these. 



ception time, which is the additional time neces- 

 sary for him to appreciate the nature of the 

 sensation, e.g., whether a light was red or blue: 

 S'^, the choice or will time, which is the additional 

 time necessary to react in a certain way on the 

 reception of a certain sensation, e.g., to press a 

 key with the right hand when the red light ap- 

 pears, with the left hand or not at all for the blue 

 light. Dr. J. M. Cattell, in a recent re investiga- 

 tion of a large part of the field, has brought to- 

 notice several new facts, and has improved the 

 method in many respects. To insure himself 

 against any variations in the working of his ap- 

 paratus. Dr. Cattell devised a means of control- 

 ling it, an essential part of the device being the de- 

 termination of the most suitable strength of current 

 for running the chronoscope. The time is recorded 

 on a Hipp chronoscope, which, by the release of a 

 magnet and the springing back of the same, re- 

 cords intervals of one one-thousandth of a second. 

 A falling screen, at a point in its fall, suddenly 

 reveals a card or color, if that is the sense-stimu- 

 lus, or can convey a shock to the finger, etc., and 

 at the same time releases the magnet of the 

 chronoscope, and sets the hands of the clock in 

 motion. The reaction of the observer is made 

 either by closing a key connected with the chrono- 

 scope with his hand, or by speaking through a 

 tube, which, like the hand-key, has the effect of 

 instantly stopping the clock. One can then read 

 on the chronoscope the interval of time between 

 the two events. In this way it was found, as th6 

 result of 520 experiments on each of two observers 

 extended over a period of six months, that the 

 reaction time for daylight, reflected from a white 

 surface, was quite constant, and was about .149 of 

 a second (strictly, .151 of a second for one, .147 of 

 a second for the other observer), it being imma- 

 terial whether the reaction was made with the 

 right or the left hand. But it takes .030 of a 

 second longer to record the reaction by moving the 

 lips. It is usually considered that the state of the 

 attention has most effect on the reaction time ; 

 but Dr. CatteU found that the disturbance caused 

 by the ticking and ringing of metronoaies with 

 bell attachments affected the reaction very slightly 

 indeed, and explains this divergence from the re- 

 sults of other experimenters, by the unusual 

 amount of practice which he had in such experi- 

 ments. In other words, the process was too auto- 

 matic to be affected seriously by the attention. 

 Again : if the attention be distracted by the men- 

 tal operation of repeatedly adding 17 to a series of 

 numbers, the time is more seriously lengthened ; 

 and, if the observer makes a great effort to attend, 

 the time can be slightly shortened. He also shows 

 that this extreme state ot attention can be main- 



