Bauhaus-Universität Weimar

Titel:
Experimental Psychology: A Manual of Laboratory Practice, Vol. II: Quantitative Experiments, part 1: Student's Manual
Person:
Titchener, Edward B.
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit16066/29/
§ 2. Mental Measurement xxv 
think of a brightness or a tone of given intensity as a sensation 
magnitude, as itself measurable. Now the stimulus is measur¬ 
able : we can measure, in terms of some unit, the amplitude of 
vibration of the ether or air waves : we have our three terms to 
measure with. But the sensation, the brightness or the tone, is 
just a single point upon the sense scale,—no more measurable, 
of itself, than is ‘the highest point’ of Mt. Vesuvius. The only 
thing that we can measure is the distance between two sensa¬ 
tions or sense points, and to do this we must have our unit step 
or unit distance. 
Let us take some instances. Suppose that two rooms of 
equal dimensions are illuminated by two ground glass globes, 
the one containing five and the other two incandescent lights of 
the same candle-power. We can say, by eye, that the illumina¬ 
tion of the first room is greater than that of the second. How 
much greater, we cannot possibly say. Even if the globes are 
removed, so that we can count the lights, we cannot say. The 
stimuli stand to one another in the ratio 5 : 2. But the corre¬ 
sponding sensations are simply different as more and less, the one 
a ‘ more bright ’ and the other a ‘ less bright.’ The brightness 
of the lighter room does not contain within it so and so many 
of the brightnesses of the darker room. Each brightness is one 
and indivisible. What we have given is rather this : that on the 
scale of brightness intensities, which extends from the just notice¬ 
able shimmer of light to the most dazzling brilliance that the eye 
can bear, the illumination of the one room lies higher, that of 
the other room lower. There is a certain distance between them. 
If we can establish a sense unit for this distance, we shall be 
able to say that the greater brightness is, in sensation, so and so 
many times removed from the lesser brightness ; just precisely 
as the top of the mountain, in terms of the 1 ft. unit, is 4200 
times removed from the bottom. Neither of the two bright¬ 
ness sensations is itself a magnitude. The magnitude is the 
distance which separates them on the intensive brightness 
scale. 
Again : we can say by ear that the roar of a cannon is louder, 
very much louder, than the crack of a pistol. But the cannon 
roar, as heard, is not a multiple of the pistol crack, does not con-
        

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