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🥸intro to psychology review

Just Noticeable Difference

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The just noticeable difference (JND) is the smallest detectable change in a stimulus that can be perceived by an individual. It is the minimum amount of change in a sensory input that a person can detect, representing the limit of their sensory discrimination ability.

5 Must Know Facts For Your Next Test

  1. The just noticeable difference is the smallest change in a stimulus that can be reliably detected by an individual.
  2. The JND is influenced by the type of sensory modality, the intensity of the original stimulus, and individual differences in sensory acuity.
  3. Weber's Law states that the JND is proportional to the magnitude of the original stimulus, meaning the larger the original stimulus, the larger the JND.
  4. The JND is an important concept in psychophysics, as it helps determine the limits of human sensory perception and the ability to discriminate between different stimuli.
  5. Understanding the JND is crucial in the design of various products and technologies, as it helps ensure that changes in sensory input can be detected by the intended users.

Review Questions

  • Explain the relationship between the just noticeable difference and the absolute threshold.
    • The just noticeable difference (JND) and the absolute threshold are related concepts in sensory perception. The absolute threshold is the minimum amount of stimulus energy required for a person to detect the presence of a stimulus 50% of the time, while the JND is the smallest detectable change in a stimulus that can be perceived. The JND is typically larger than the absolute threshold, as it represents the minimum change in a stimulus that can be reliably detected, rather than just the presence of the stimulus.
  • Describe how Weber's Law relates to the just noticeable difference.
    • Weber's Law states that the just noticeable difference (JND) is proportional to the magnitude of the original stimulus. This means that as the intensity of a stimulus increases, the minimum change required for the difference to be detected also increases. For example, the JND for a 10-gram weight would be smaller than the JND for a 100-gram weight. This relationship between the JND and the original stimulus magnitude is a fundamental principle in the study of sensory perception and psychophysics.
  • Analyze the importance of the just noticeable difference in the context of sensation and perception.
    • The just noticeable difference (JND) is a crucial concept in the study of sensation and perception because it represents the limits of human sensory discrimination. Understanding the JND helps researchers and designers determine the smallest changes in sensory input that can be reliably detected by individuals. This knowledge is essential for the design of various products and technologies, as well as for understanding the capabilities and limitations of human sensory systems. By knowing the JND, researchers can better understand how people perceive and interact with their environment, which has important implications for fields such as psychology, ergonomics, and user experience design.