lo T. L. Bolton and Donna L. IVithey 



under active palm pressure, and 155, 160, and 170 do to the 

 standard under finger pressure with arm reaction : 



Passive palm pressure (150)82.7 (170)62.4 (190)44.1 (210)15.5 



Active palm pressure (150)89.0 (160)69.3 (170)41.1 (190)18.1 



Pressure with arm reaction. .. (150)81.1 (155)64.0 (160)41.75 (170)13.6 



The percentages of correct judgments under the standard are 

 ' fairly constant throughout all the sets of experiments, the aver- 

 age being 83.2 per cent. The perception of sameness is a very 

 definite thing and hence difficult to make. From these experi- 

 ments it would seem that there is a strong probability that, when 

 the heaviest stimulus magnitude is easily discernible from the 

 standard, and there is, between the heaviest and standard, a series 

 of stimulus magnitudes diflfering by equal steps, the standard will 

 be judged the same something more than 80 per cent of the time. 

 Even the experienced reagents who know the conditions under 

 which the observations are taken must find themselves sorely 

 pressed by the fact that between the double pressures five out of 

 six times the second is actually heavier. The various influences 

 that combine to fix the number of correct judgments under the 

 standard and the compared pressures will come up again for dis- 

 cussion. Our table here shows what stimulus magnitudes are 

 alike for judgment or sensation. 



After the conclusion of the third set of experiments some ob- 

 servations were taken upon passive palm pressure to discover 

 whether any perceptible effect had been made in practice increase. 

 Eighteen series of observations were taken upon both the experi- 

 enced reagents. The percentages of S. judgments to the number 

 of series are given in the following tabular statement: 



S. M. Reagent W. Reagent B. 



150 76.2 83.3 



170 61.0 61.0 



190 22.3 27.8 



210 16.6 16.6 



230 00.0 11.5 



Only under the stimulus magnitude 190 does there seem to be 

 any change in the direction of practice effect. Here the reduc- 

 tion is about 18 per cent. The irregularities are too great to 

 make this reduction certainly due to practice effect or other sim- 



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