The absolute threshold for human hearing demonstrates high sensitivity; under ideal quiet conditions, the hair cells within the inner ear are capable of detecting the sound of a clock ticking from 20 feet away.

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The absolute threshold is a measure of sensory system sensitivity, defined as the minimum stimulus energy needed for detection 50% of the time. This can be thought of as the faintest light or softest sound that can be perceived half the time. These thresholds are typically measured under highly controlled, optimal conditions to ensure accuracy.

Absolute Threshold

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Subliminal messages are stimuli presented below the absolute threshold for conscious awareness. Although these stimuli are potent enough to activate sensory receptors and trigger nerve impulses to the brain, they are not consciously perceived. While research in laboratory settings has shown that individuals can process and react to information outside of their awareness, these hidden messages have been found to have very little influence on behavior in real-world contexts.

Subliminal Messages

The just noticeable difference (jnd), also known as the difference threshold, refers to the minimum change in stimulus energy that is required for an observer to detect a difference 50% of the time. Unlike the absolute threshold, the difference threshold is not a fixed value; it changes depending on the intensity of the original stimulus, a principle described by Weber's Law.

Just Noticeable Difference (jnd) or Difference Threshold

An illustration of the remarkable sensitivity of human vision is that on a clear, dark night, the most sensitive receptor cells in the eye can perceive the flame of a candle from a distance of 30 miles.

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