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Weber's Law of Just Noticeable Differences

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What is Weber’s Law of Just Noticeable Differences

Weber's Law of Just Noticeable Differences (JND) is a fundamental psychological principle that describes how humans detect differences in the strength of sensory stimuli. This law was first established in the mid-nineteenth century by Ernst Weber, a German physician, and has since been extensively studied and utilized in a variety of domains, including psychophysics, marketing,UX, and economics.

Weber's Law asserts that the Just Noticeable Differences between two stimuli is proportional to their size, which means that the larger the stimulus, the greater the difference must be for it to be recognized. For example, if a person is holding a 100-gram weight and is asked to detect a weight shift, they must add more than 10 grams (the JND) for the difference to be noticed. If they are carrying a 1-kilogram weight, the JND will be significantly larger, and they will need to add more than 100 grams to notice the difference.

This law applies to all senses, including vision, hearing, touch, taste, and smell. The JND, for example, is related to the brightness or color of an item in vision, but it is associated to the loudness or pitch of a sound in hearing. Weber's Law also applies to more complicated stimuli like prices, where the Just Noticeable Differences is proportional to the absolute value of the price difference.

Application of Weber's law of just noticeable differences in UX development

According to Weber's law of just noticeable difference, customers abhor dramatic changes; therefore, if you must make a significant change to your design, make it gradually.
While updating the design, it also advisable to make small interactions with users about their user experiences.

Effect of dramatic changes

  1. User familiarity: Over time, users grow accustomed to a specific interface and how it operates. This familiarity can be upset by significant changes, which can leave users perplexed and frustrated as they try to use the new interface.
  2. Learning curve: Users may need to relearn how to use specific features or traverse the interface when an interface gets a significant makeover.
  3. Cognitive load: A significant shift in UX design may make it more difficult to use the interface. Users may have a worse user experience since it takes more mental effort for them to comprehend the new design and adjust to the changes.
  4. Trust: Users gradually come to trust an interface, and rapid changes might erode that confidence. Users may believe that the designers are not attentive to their wants and preferences if an interface changes significantly without prior notice or justification.

Example of a real-world application of Weber's law.

Let take a look at microsoft logos since 1990


When Microsoft usually redesigned its Windows logo, the design team likely took into account the just noticeable differences to ensure that the changes made to the logo were noticeable but not too drastic.The redesign aimed to modernize the logo while retaining its core elements and brand recognition.

Finally, the just noticeable difference can be used to determine the minimum amount of change needed to make a noticeable difference while retaining the recognizability and brand identity of the previous design.

Weber's Law of Just Noticeable Differences
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