Reaction time
From Wikipedia, the free encyclopedia
Reaction time (RT) is the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response. RT is often used in experimental psychology to measure the duration of mental operations, an area of research known as mental chronometry. The behavioral response is typically a button press but can also be an eye movement, a vocal response, or some other observable behavior.
RT is fastest when there is only one possible response (simple reaction time) and becomes slower as additional response options are added (choice reaction time). According to Hick's law, choice reaction time increases in proportion to the logarithm of the number of response alternatives. The law is usually expressed by the formula RT = a + blog2(n + 1), where a and b are constants representing the intercept and slope of the function, and n is the number of alternatives.[1]
Reaction time is quickest for young adults and gradually slows down with age. It can be improved with practice, up to a point, and it declines under conditions of fatigue and distractions. Reaction time is generally faster in males than in females.[2]
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[edit] History
The Muslim scientist, Abū Rayhān al-Bīrūnī was the first person to describe the concept of reaction time:[3]
"Not only is every sensation attended this by a corresponding change localized in the sense-organ, which demands a certain time, but also, between the stimulation of the organ and consciousness of the perception an interval of time must elapse, corresponding to the transmission of stimulus for some distance along the nerves."
The first scientist to measure reaction time in the laboratory was Franciscus Donders. Donders found that simple reaction time is shorter than recognition reaction time, and that choice reaction time is longer than both.[4] Donders also devised a subtraction method to analyze the time it took for mental operations to take place. By subtracting simple reaction time from choice reaction time, for example, it is possible to calculate how much time is needed to make the choice.
[edit] Measurement
Simple reaction time is the time required for an observer to respond to the presence of a stimulus. For example, a subject might be asked to press a button as soon as a light or sound appears. Mean RT for young adults is approximately 190 milliseconds to a detect visual stimulus, and approximately 160 milliseconds to detect an auditory stimulus.[5]
Go/No-Go reaction time tasks require that the subject press a button when one stimulus type appears and withhold a response when another stimulus type appears. For example, the subject may have to press the button when a red light appears and not respond when a green light appears.
Choice reaction time tasks require distinct responses for each possible class of stimulus. For example, the subject might be asked to press one button if a red light appears and a different button if a yellow light appears. The Jensen Box is an example of an instrument designed to measure choice reaction time.
Discrimination reaction time involves a subject comparing pairs of simultaneously presented visual displays and then pressing one of two buttons according to which display appears brighter, longer, heavier, or greater in magnitude on some dimension of interest.
Due to momentary attentional lapses, there is a considerable amount of variability in an individual's reaction time. To control for this, researchers typically require an subject to perform multiple trials, which are then averaged to provide a more reliable measure.
[edit] RT and cognitive ability
Researchers have reported modest, but statistically significant correlations between measures of reaction time and intelligence. Although there are numerous exceptions, there is an overall tendency for individuals with higher IQ to be slightly faster on reaction time tests. One study found a weak association between simple reaction time and intelligence (r=−.31), and a moderate association between choice reaction time and intelligence (r=−.49).[6] This relationship may be due to more efficient information processing or better attentional resources in more intelligent people.
[edit] See also
[edit] References
- ^ Hick's Law at Encyclopedia.com Originally from Colman, A. (2001). A Dictionary of Psychology. Retrieved February 28, 2009.
- ^ Der, G., & Deary, I. J. (2006). Age and sex differences in reaction time in adulthood: Results from the United Kingdom health and lifestyle survey. Psychology and Aging, 21, 62-73.
- ^ Iqbal, Muhammad, "The Spirit of Muslim Culture", The Reconstruction of Religious Thought in Islam, http://www.allamaiqbal.com/works/prose/english/reconstruction, retrieved on 2008-01-25
- ^ Kosinski, R. J. (2008). A literature review on reaction time, Clemson University.
- ^ Kosinski, R. J. (2008). A literature review on reaction time, Clemson University.
- ^ Deary, I. J., Der, G., & Ford, G. (2001). Reaction times and intelligence differences: A population-based cohort study. Intelligence, 29, 389–399.
[edit] External links
[edit] Additional information
- A Literature Review on Reaction Time by Robert J. Kosinski, Clemson University
- Historical Background by Museum of the History of Reaction Time Research
- Fingertip Reaction Time by The Physics Factbook
[edit] Online tests
- Simple visual reaction time from Human Benchmark
- Simple visual reaction time from Cognitive Fun
- Simple auditory reaction time from Cognitive Fun
- Go/No-go visual reaction time from Cognitive Fun
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