Definition

1. Noun:
   • A psychophysical principle: Fechner's law is a concept in psychophysics stating that the perceived magnitude of a sensation increases in proportion to the logarithm of the physical intensity of the stimulus. It builds upon the foundational work of Ernst Heinrich Weber.

Usage

• Noun:
  • Fechner's law describes the mathematical relationship between stimulus strength and perceived intensity.
  • According to Fechner's law, doubling the physical intensity of a light does not double its perceived brightness.
  • The classic example illustrating Fechner's law is that adding one candle to a room already lit by ten candles creates a noticeable change, but adding one candle to a room lit by a hundred candles is hardly perceptible.

Advanced Usage

• "Weber-Fechner law": This is a common combined term referencing the continuum from Weber's findings on the just-noticeable difference to Fechner's formalized logarithmic law.
  • The Weber-Fechner law is a cornerstone of classical psychophysics.

Variants and Related Words

• Psychophysics (n): The branch of psychology that deals with the relationships between physical stimuli and mental phenomena.
• Logarithmic (adj): Relating to or expressed in terms of logarithms.
• Stimulus Intensity (n): The magnitude or strength of a physical stimulus.

Synonyms

• Weber-Fechner law: The combined principle often used synonymously, though technically Weber's and Fechner's contributions are distinct steps.
• Logarithmic law of sensation: A descriptive synonym highlighting the mathematical form of the relationship.

Related Concepts

• Weber's law: The principle that the just-noticeable difference between two stimuli is proportional to the magnitude of the original stimulus. This is the empirical finding upon which Fechner's law is mathematically derived.
• Steven's power law: A later, alternative model in psychophysics proposing that sensation is related to stimulus intensity by a power function, not a logarithmic one.

Noun

1. (psychophysics) the concept that the magnitude of a subjective sensation increases proportional to the logarithm of the stimulus intensity; based on early work by E. H. Weber