Absolute threshold

Under an absolute threshold ( engl. Absolute threshold) is understood in psychology, the lowest intensity of a stimulus that results in a reportable perception of the observer. This is the minimum amount of physical energy that just yet evokes a sensory experience.

Together with the difference threshold, they form the central concepts of classical psychophysics and are still object of investigation of experimental psychology. The task of a subject is the discovery ( detection) of a stimulus. The reciprocal of the absolute threshold is the sensitivity.

Exceeded stimuli not the absolute threshold, it is called subliminal stimuli ( see also subliminal ).

Types of absolute thresholds

For any specific absolute Reizmodalität thresholds can be determined ( seeing, hearing, smelling ). At a very early experiment examined Hecht, Shlaer and Pirenne in 1942, how many photons are needed at least to be perceived by the human eye. The approximate thresholds familiar events Zimbardo describes as follows:

  • Sound: The ticking of a clock without ambient noise can be perceived from about 6 feet away.
  • Taste: A teaspoon of sugar to about 7.6 liters of water can be tasted.

Determination of absolute thresholds

There are three classical methods for threshold determination:

  • Constance method
  • Production method
  • Method of limits

In reality you can find people for no individual value from which they always detect a stimulus. Therefore, the definition of the absolute threshold is in practice - by convention - adapted and defined as the stimulus intensity at which one perceives the stimulus with 50 % probability. This probability can be represented by a psychometric function and read to her.

Signal detection theory

The ability to perceive a weak stimulus is affected by several other factors. Around the emotional state, experiences, expectations, or motivation, attention and vigilance. If you want response tendencies (one person always says very late that it detects a signal) into account, the signal detection theory provides a suitable measure of the quality of a person's decision.

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