Definition

1. Noun:
   • A principle in psychophysics: Weber's law states that the smallest detectable change in a stimulus (the just-noticeable difference) is a constant proportion of the original stimulus intensity.

Usage

• Weber's law is used to describe and predict human sensory perception. It is a foundational concept in experimental psychology and psychophysics.
• It is typically cited in academic or scientific contexts when discussing the relationship between the physical magnitude of a stimulus and its perceived intensity.

Examples

• Noun:
  • Weber's law helps explain why adding one candle to a dark room is noticeable, but adding one candle to a brightly lit room is not.
  • According to Weber's law, the just-noticeable difference for weight is roughly a constant fraction of the initial weight.

Advanced Usage

• "Weber fraction": The constant ratio (k) in the formula ΔI/I = k, where ΔI is the just-noticeable difference and I is the original stimulus intensity. This fraction is specific to each type of sensory modality (e.g., brightness, loudness, weight).
  • The Weber fraction for lifted weight is approximately 1/50.

Variants and Related Words

• Weber-Fechner law: A related, more general psychophysical law that builds upon Weber's law to describe the relationship between stimulus magnitude and subjective sensation.
• Just-noticeable difference (JND): The minimal change in a stimulus that can be detected; the key variable described by Weber's law.
• Psychophysics: The branch of psychology that deals with the relationships between physical stimuli and mental phenomena, which is the field where Weber's law is applied.

Synonyms

• Weber's principle: A less common synonym.
• Law of comparative judgment: A related but broader theoretical framework.

Related Phrases

• "To obey Weber's law": Used to describe a sensory modality where the just-noticeable difference is proportional to stimulus intensity.
  • The perception of loudness roughly obeys Weber's law across a wide range of intensities.

Noun

1. (psychophysics) the concept that a just-noticeable difference in a stimulus is proportional to the magnitude of the original stimulus
   • Weber's law explains why you don't notice your headlights are on in the daytime