Absolute threshold
Under an absolute threshold (Engl. Absolute threshold ) is understood in psychology , the lowest intensity of a stimulus that leads to a reportable perception the observer. It is the minimum of physical energy that just evokes a sensory experience. In sensory physiology , this sensory threshold is also referred to as the stimulus threshold .
Together with the difference threshold, they form the central concepts of classical psychophysics and are still the subject of investigation in experimental psychology today . The task of a subject is the discovery ( detection ) of a stimulus. The reciprocal of the absolute threshold is the sensitivity.
If stimuli do not exceed the absolute threshold, one speaks of subliminal stimuli (see also subliminal ).
Types of absolute thresholds
Specific absolute thresholds can be determined for each stimulus modality (sight, hearing, smell). In a very early experiment in 1942, Hecht, Shlaer and Pirenne investigated the minimum number of photons required to be perceived by the human eye. Zimbardo describes the approximate thresholds of familiar events as follows:
- Light: The flame of a candle can be seen from around 50 km away on a dark, clear night.
- Sound: The ticking of a clock without ambient noise can be heard from about 6 meters away.
- Taste: One teaspoon of sugar in about 7.6 liters of water can be tasted.
Determination of absolute thresholds
There are three classic methods for determining thresholds:
In reality, it is not possible to determine an individual value for people from which they can always detect a stimulus. This is why the definition of the absolute threshold is adapted in practice - by convention - and defined as the stimulus intensity from which there is a 50% probability that the stimulus will be perceived. This probability can be represented and read off from a psychometric function .
Signal discovery theory
The ability to perceive a weak stimulus is influenced by several other factors. For example the mental state, experiences, expectations or motivation, attention and vigilance. If one wants to consider response tendencies (a person always says very late that they recognize a signal), signal discovery theory offers a suitable measure of the quality of a person's decision.
Individual evidence
- ↑ Herbert Hagendorf, Joseph Krummenacher, Hermann-Joseph Müller, Torsten Schubert: General Psychology for Bachelor: Perception and Attention . Jumper; Edition: 2011 (March 18, 2011). ISBN 978-3642127090 . Page 44.
- ^ A b Richard J. Gerrig, Philip G. Zimbardo: Psychology . Addison-Wesley Verlag; Edition: 18th, updated edition (March 20, 2008). ISBN 978-3827372758 . Page 114ff.
- ↑ David G. Myers: Psychology . Jumper; Edition: 2nd exp. u. updated edition 2008 (July 14, 2008). ISBN 978-3540790327 . Page 216/217.