The Weber–Fechner law refers to two related laws in the field of psychophysics, known as Weber’s law and Fechner’s law. Both laws relate to human perception, more specifically the relation between the actual change in a physical stimulus and the perceived change. This includes stimuli to all senses: vision, hearing, taste, touch, and smell.
Both Weber’s law and Fechner’s law were formulated by Gustav Theodor Fechner (1801–1887). They were first published in 1860 in the work Elemente der Psychophysik (Elements of psychophysics). This publication was the first work ever in this field, and where Fechner coined the term psychophysics to describe the interdisciplinary study of how humans perceive physical magnitudes.

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  1. shinichi says:

    Weber–Fechner law



    Gustav Fechner


    Gustav Theodor Fechner (1801 – 1887), was a German philosopher, physicist and experimental psychologist. An early pioneer in experimental psychology and founder of psychophysics, he inspired many 20th century scientists and philosophers. He is also credited with demonstrating the non-linear relationship between psychological sensation and the physical intensity of a stimulus via the formula: S=K\ln I, which became known as the Weber–Fechner law.

  2. shinichi says:


    Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they produce. Psychophysics has been described as “the scientific study of the relation between stimulus and sensation” or, more completely, as “the analysis of perceptual processes by studying the effect on a subject’s experience or behaviour of systematically varying the properties of a stimulus along one or more physical dimensions”.

    Psychophysics also refers to a general class of methods that can be applied to study a perceptual system. Modern applications rely heavily on threshold measurement, ideal observer analysis, and signal detection theory.

    Psychophysics has widespread and important practical applications. For example, in the study of digital signal processing, psychophysics has informed the development of models and methods of lossy compression. These models explain why humans perceive very little loss of signal quality when audio and video signals are formatted using lossy compression.



    Neuropsychology is the study of the structure and function of the brain as they relate to specific psychological processes and behaviours. It is an experimental field of psychology that aims to understand how behavior and cognition are influenced by brain functioning and is concerned with the diagnosis and treatment of behavioral and cognitive effects of neurological disorders. Whereas classical neurology focuses on the physiology of the nervous system and classical psychology is largely divorced from it, neuropsychology seeks to discover how the brain correlates with the mind. It thus shares concepts and concerns with neuropsychiatry and with behavioral neurology in general. The term neuropsychology has been applied to lesion studies in humans and animals. It has also been applied in efforts to record electrical activity from individual cells (or groups of cells) in higher primates (including some studies of human patients). It makes use of neuroscience, and shares an information processing view of the mind with cognitive psychology and cognitive science.

    In practice, neuropsychologists tend to work in research settings (universities, laboratories or research institutions), clinical settings (medical hospitals or rehabilitation settings, often involved in assessing or treating patients with neuropsychological problems), or forensic settings or industry (often as clinical-trial consultants where CNS function is a concern).

  3. shinichi says:


    精神物理学(psychophysics)は外的な刺激と内的な感覚の対応関係を測定し、また定量的な計測をしようとする学問である。認知科学や工学の分野では心理物理学と呼ばれることが多い。グスタフ・フェヒナーがその創始者であり、心理学(実験心理学)の成立に大きな影響を与えた。 外的な刺激は物理量として客観的に測定できる。そこで外的な刺激と内的な感覚との対応関係が分かれば、内的な感覚も客観的に測定できることになる。

    主な感覚はいわば五感を中心とした知覚(視覚、聴覚、嗅覚、味覚、平衡感覚、皮膚感覚、深部感覚、内臓感覚など)に代表される。これらの知覚は視覚であれば目、味覚であれば舌、平衡感覚は内耳など、いくつかの受容器によって引き起こされることは古代よりわかっていた。またこれらを解剖しその機構は科学の発展によりかなりの部分が解明されるようになっていた。 たとえば人間の視覚器官である眼と比較すると、カメラは非常によく似た機構をもっている。 水晶体はレンズに、網膜はフィルムに該当するといった具合である。 ここで、私たちは網膜に映った映像を認識しているわけであるが、その映像は外部から入ってきた光によるものである。 この光は物理的なものであるので、測定が可能である。こういった質的な出来事と感覚との対応関係を物理的な、いわば人間の知覚をブラックボックスと見ていくのが精神物理学である。

    心身と外的刺激の関係性を明らかにする過程において、精神物理学関数というものが考案された。 これは、各種刺激と感覚との関係を物理学的な(あるいは数学的な)方法で表記するものである。




  4. shinichi says:




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