60 MATHEMATICAL BIOPHYSICS OF THE CENTRAL NERVOUS SYSTEM 



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Figure 3. — Comparison of theory with experiment: distribution of judgments 

 of relative brightness. Curve, theoretical from equations (l)-(5) ; points, experi- 

 mental (Kellogg, 1930). The ordinate is the difference between the intensities 

 of the "variable" and the "standard" stimuli, in meter-candles. The abscissa is 

 in every case the proportion of judgments of the type in question: for the solid 

 circle, "greater than" categorical judgment; for the open circle, "greater than" 

 with "doubtful" judgments permitted; for the crosses, the proportion of "doubt- 



