September 12, 1890.] 



SCIENCE. 



145 



or sensory ; nor is it necessary that the same mode of re-action 

 be followed in all cases. The possibilities thus are (1) that 

 both the simple and the subjective times will be sensory; (2) 

 both motor; or (3) the simple sensory, and the other motor; 

 or (4) the simple motor, and the other sensory. (1) This 

 seems to be the mode best suited to the subjective method. 

 It supposes the processes to take place serially, and the sim- 

 ple time not to involve the recognition of the specific nature 

 of the impression. (2, 3) If the subjective distinction is made 

 on the motor plan, it can only mean that the re-action takes 

 place too soon, and that the distinction is really made after 

 the movement has been made. In this case the distinction 

 time would be too small. (3) probably does not occur. (4) 

 is apt to occur, and would yield a very long distinction time. 

 That these considerations are practically important can be 

 illustrated by Tischer's results upon nine subjects with sound 

 re-actions and distinctions. The average of the nine gives a 

 distinction time of ISQo', and a simple time of 118(7. Four 

 of the subjects evidently make use of the motor re-action, 

 their simple time being 107(7, and their subjective distinction 

 116(7; i.e., they anticipate the distinction. Berger and Cat- 

 tell express the same difficulty, and for this reason discarded 

 the method. Their simple re-action to weak light was IQSff, 

 with distinction of intensity 208(7. Two of the subjects 

 evidently re-act according to the sensory method, their sim- 

 ple re-action being 141(7, and the subjective distinction 246(7. 

 That these are not individual differences is shown by the 

 fact that the adaptive re-actions are about alike in all. 

 Similarly with regard to the difference between the simple 

 and the incomplete re-action times. If both are sensory in 

 character, we might expect that the incomplete would be 

 longer by the addition of an easy distinction and choice, and 

 this seems tolse only a slight addition. Bonders, and those of 

 Tischer's subjects who re-act by the sensory method, show a 

 relatively small difference, though this is not true of Friede- 

 rich's subjects. While Tischer's "motor" subjects show a 

 difference of 159(7 between the simple and the incomplete, 

 the "sensory" subjects show one of only 61(7. (2, 3) If the 

 incomplete re-action is motor in form, the difference between 

 it and the simple re-action will be very small; more so in (3) 

 than in (2), though (3) is not likely to be used. The expec- 

 tation is entirely directed to the stimulus upon which re- 

 action is to follow, and the fact that other stimuli may ap- 

 pear hardly enters into the experiment. Under this head it 

 seems fair to classify the results of Kries and Auerbach, 

 who, with clearly motor re-actions, find a difference of 30-40(7 

 for (XXX.-XXXVJ. ) a variety of incomplete re-actions. (4) 

 It is much more likely that the change from the simple to the 

 incomplete form of re-action will bring with it an attention 

 to the sensory part of the process, and thus make the differ- 

 ence between it and the simple time long. This seems to be 

 the case with Berger and Cattell, who, with a simple re- 

 action time of 147(7 and 150(7, have an incomplete re-action 

 time of 306(7 and 277(7. The difference between the incom- 

 plete and the adaptive re-action seems to be uniformly small 

 (many of the differences being not far from 40(7), though 

 the individual variations are considerable. It is likely that 

 the effects attributed to practice and fatigue may really be 

 due to a change from the sensory to the motor form of re- 

 action. Thus Kries and Auerbach mention that their incom- 

 plete times were at first very long, but that they became very 

 small, the reduction continuing long after the effect of prac- 

 tice upon the simple re-action had ceased. Again, the fact 

 that simple re-action times are long when following complex 

 ones, or that subjective times are longer when following 

 adaptive re-actions, seems to be not so much the effect of 

 fatigue as of a continuance of a sensory mode of re-action. 

 It should also be mentioned that Tigerstedt ingeniously 

 proposes to measure the distinction time by taking the differ- 

 ence between two incomplete re-actions, in one of which we 

 re-act to a definite simple impression, and in the other to the 

 impression requiring distinction (e.g., in one series I re-act 

 to white, but not to a color ; in the other, to a color, but not 



to white) ; and the difference in time will be needed for 

 distinguishing a color from white. The general fact re- 

 mains, then, that while the combined distinction and choice 

 times exhibit only such individual and other variations as 

 seem explicable by the differences in the conditions of ex- 

 periment (the adaptive re-action times of eight of Tischer's 

 nine subjects fall between 293 and 320(7), the estimates that 

 have been attempted of the portions of the time due to dis- 

 tinction and to choice separately, show such large variations 

 as to force the conviction that the different experimenters 

 were not measuring the same processes. 



Conditions Affecting^ Distinction and Choice. 

 Bearing in mind that we are dealing with comparative re- 

 sults only, — comparisons restricted mainly to the results of 

 the same observer, obtained by the same method, — we pro- 

 ceed to investigate the conditions by which these processes 

 involving distinction and choice are affected. It will be 

 convenient to begin witVi the effect of (1) the number of dis- 

 tinctions and of choices. The effect of the number of ob- 

 jects among which distinction is to take place, upon the time 

 needed to make the distinction, is best shown in the "incom- 

 plete " and subjective methods, in which the range of dis- 

 tinction may be varied without affecting that of choice. 

 For example: Cattell makes an incomplete re-action to a 

 certain color when either that or one other color may appear in 

 306(7, when either that or any one of nine other colors may 

 appear (IV. and V.) in 313(7. Friederich's subjects make a 

 subjective distinction between two colors in 267(7, betweenfour 

 in 296(7 (XXXIX. and XL.). Six of Tischer's subjects make 

 a subjective distinction between two sounds of different inten- 

 sity in 146(7 (simple re-action, 114(7); between three sounds, 

 in 164(7; four sounds, in 178(7; five sounds, in 194(7 (XLIV. 

 and XLVII.). Other experiments cited in the table show the 

 same slight increase of distinction time vfith the increase of 

 the range of impressions, but complicated with other factors 

 as well. With regard to the effect upon the choice time 

 when the number of possible choices increases, we have the 

 results of Merkel, who found for the simple re-action time of 

 ten subjects to visual impressions 188(7; for an adaptive re- 

 action between two impressions, 276(7; between three, 330(7; 

 between four, 394(7; between five, 445(7; between six, 489(7; 

 between seven, 526(7; between eight, 562(7; between nine, 

 581(7; and between ten, 588(7 (partially cited in XLVIII.- 

 LII.). The impressions were the numbers 1, 2, 3, 4, 5, and I., 

 II., III., IV., and V. The re-actions to movements of the ten 

 fingers naturally associated with these impressions, and the 

 naturalness of this association doubtlessly contributes to the 

 small increase in time. Miinsterberg called these numbers 

 and re-acted in the same way, finding for a choice between 

 five movements 383(7, and between ten 478(7 (simple re-action 

 being 1620^). It being established that but a small share of 

 the increase is due to the distinction (Merkel has experimen- 

 tally shown this for his subjects), we may conclude, that, 

 with an increase in number, the difficulty of choice increases 

 more rapidly than the difficulty of distinction. In addition, 

 we have reason to believe that the increase would be still 

 more marked in case the association between impression and 

 motion is artificial. When this association reaches the 

 maximum of naturalness, in naming objects, the increase 

 with the number of impressions is slight. Thus it may be 

 calculated from Cattell's results that it takes him but about 

 10(7 longer to name 26 letters or short words than to name 



