Weber's Fraction（韋伯分數）

WEBER'S LAW, in psychology, the name given to a principle first enunciated by the German scientist, Ernst Heinrich Weber (1795-1878), who became professor at Leipzig (of anatomy, 1818, of physiology, 1840).

He was-specially famous for his researches into aural and cutaneous sensations. His law, the purport of which is that the increase of stimulus necessary to produce an increase of sensation in any sense is not a fixed quantity but depends on the proportion which the increase bears to the immediately preceding stimulus, is the principal generalization of that branch of scientific investigation which has come to be known as psycho-physics

1834年由德國生理學家韋伯所提出：

人體感覺的科學性，稱為韋伯定律。（Weber's law）

他發現人類各種感覺，其差異閾限與標準刺激之間，成定比的關係。

韋伯定律公式如下：

JND/S=K

JND意指：可知覺的最小變化量（差異閾限）

S意指：標準刺激（標準刺激強度）

K則是：韋伯常數（韋伯分數）

以重量大小的判斷來為例，讓受試者閉上眼睛，用手比較兩個物體的重量。

假設一百公克為標準刺激，受試者在一百零三公克時，恰好能夠辨別這兩者差異，則三公克即為「差異閾限」。

假設標準刺激為兩百公克，受試者在兩百零六公克時，才能辨別兩者的差異。

由韋伯定律可以得到以下比值：

3/100=6/200=9/300=12/400=15/500=K

由上敘比值可知：重量一百公克時，只需加上三公克，即可感覺其差異，

兩百公克時，必須加上六公克才有感覺差異，依此類推。