Judgments Are Relative, Not Absolute
During his research on kinesthesis, Weber made the star- tling observation that the jnd is a constant fraction of the standard weight. For lifted weights, that frac- tion is 1/40; for nonlifted weights, it is 1/30. Using lifted weights as an example, if the standard weight is 40 grams, the variable weight would have to be 41 grams to be judged heavier or 39 grams to be judged lighter than the standard. If the standard weight is 160 grams, the variable weight would have to be 164 grams or 156 grams to be judged heavier or lighter, respectively, than the standard. Weber then aligned himself with the large number of scientists and philosophers who found that there was not a simple one-to-one correspondence between what is present physically and what is experienced psycho- logically. Weber observed that discrimination does not depend on the absolute difference between two weights but on the relative difference between the two or the ratio of one to the other. Weber extended his research to other sense modalities and found evi- dence that suggested that there is a constant fraction corresponding to jnds for each sense modality.
The finding that jnds corresponded to a con- stant fraction of a standard stimulus was later called Weber’s law, and it can be considered the first quantitative law in psychology’s history. This was the first statement of a systematic relationship between physical stimulation and a psychological experience. But because Weber was a physiologist, psychology was not his primary concern. It was Fechner who realized the implications of Weber’s work for psy- chology and who saw in it the possible resolution of the mind–body problem.
