Reaction time

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. In psychometric psychology it is considered to be an index of speed of processing.^[1] That is, it indicates how fast the thinker can execute the mental operations needed by the task at hand. In turn, speed of processing is considered an index of processing efficiency. 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 $RT=a+b\log _{2}(n+1)$ , where $a$ and $b$ are constants representing the intercept and slope of the function, and $n$ is the number of alternatives.^[2]

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.^[3]

History

The Persian scientist, Abū Rayhān al-Bīrūnī was the first person to describe the concept of reaction time:

"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."^[4]

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.^[5] Donders also devised a subtraction method to analyze the time it took for mental operations to take place.^[6] By subtracting simple reaction time from choice reaction time, for example, it is possible to calculate how much time is needed to make the connection.

Measurement

There are four basic means of measuring RT given different operational conditions during which a subject is to provide a desired response:

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 college-age individuals is about 160 milliseconds to detect an auditory stimulus, and approximately 190 milliseconds to detect visual stimulus.^[7]

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 green light appears and not respond when a blue 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 around Natwain 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 random variability in an individual's reaction time. To control for this, researchers typically require a subject to perform multiple trials, which are then averaged to provide a more reliable measure.

RT and cognitive ability

Researchers have reported medium-sized correlations between reaction time and measures of intelligence: There is thus a tendency for individuals with higher IQ to be faster on reaction time tests.

Research into this link of mental speed and general ability (perhaps first stimulated by Charles Spearman, was re-popularised by Arthur Jensen, and the "CHoice reaction Apparatus" associated with his name became a common standard tool in reaction time– IQ research.

The strength of the RT-IQ association is a subject of research. Several studies have reported association between simple reaction time and intelligence or around (r=−.31), with a tendency for larger associations between choice reaction time and intelligence (r=−.49). ^[8]. Much of the theoretical interest in reaction time was driven by Hick's Law, relating the slope of reaction time increases to the complexity of decision required (measured in units of uncertainty popularised by Claude Shannon as the basis of information theory). This promised to link intelligence directly to the resolution of information even in very basic information tasks. There is some support for a link between the slope of the reaction time curve and intelligence, as long as reaction time is tightly controlled ^[9]

This cause of the relationship is unclear. It may reflect more efficient information processing, better attentional control, or the integrity of neuronal processes.

As with fluid ability, RT increases in old age, and these increases are systematically associated with changes in many other cognitive processes, such as executive functions, working memory, and inferential processes. ^[10] In the theory of Andreas Demetriou, ^[11] one of the neo-Piagetian theories of cognitive development, change in speed of processing with age, as indicated by decreasing reaction time, is one of the pivotal factors of cognitive development.

References

^ Jensen, A. (2006). Clocking the mind: Mental chronometry and individual differences. Amsterdam: Elsevier.
^ 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]], retrieved 2008-01-25 {{citation}}: URL–wikilink conflict (help)
^ Kosinski, R. J. (2008). A literature review on reaction time, Clemson University.
^ Donders, F.C. (1969). On the speed of mental processes. Translated by W.G. Koster in W.G. Koster (Ed.) Attention and Performance II (pp. 412-431). Amsterdam: North Holland. (Reprinted from Onderzoekingen gedaan in het Physiologigisch Laboratorium der Utrechtsche Hoogeschool, 1868-1869, Tweede reeds, II, 92-100).
^ 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.
^ Bates, T. C., & Stough, C. (1998). Improved Reaction Time Method, Information Processing Speed, and Intelligence. Intelligence, 26(1), 53-62.
^ Demetriou, A., Mouyi, A., & Spanoudis, G. (2008). Modeling the structure and development of g. Intelligence, 5, 437-454.
^ Demetriou, A., Mouyi, A., & Spanoudis, G. (2010). The development of mental processing. Nesselroade, J. R. (2010). Methods in the study of life-span human development: Issues and answers. In W. F. Overton (Ed.), Biology, cognition and methods across the life-span. Volume 1 of the Handbook of life-span development (pp. 36-55), Editor-in-chief: R. M. Lerner. Hoboken, NJ: Wiley.

External links

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

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

[1] Jensen, A. (2006). Clocking the mind: Mental chronometry and individual differences. Amsterdam: Elsevier.

[2] Hick's Law at Encyclopedia.com Originally from Colman, A. (2001). A Dictionary of Psychology. Retrieved February 28, 2009.

[3] 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.

[4] Iqbal, Muhammad, "The Spirit of Muslim Culture", [[The Reconstruction of Religious Thought in Islam]], retrieved 2008-01-25 {{citation}}: URL–wikilink conflict (help)

[5] Kosinski, R. J. (2008). A literature review on reaction time, Clemson University.

[6] Donders, F.C. (1969). On the speed of mental processes. Translated by W.G. Koster in W.G. Koster (Ed.) Attention and Performance II (pp. 412-431). Amsterdam: North Holland. (Reprinted from Onderzoekingen gedaan in het Physiologigisch Laboratorium der Utrechtsche Hoogeschool, 1868-1869, Tweede reeds, II, 92-100).

[7] Kosinski, R. J. (2008). A literature review on reaction time, Clemson University.

[8] Deary, I. J., Der, G., & Ford, G. (2001). Reaction times and intelligence differences: A population-based cohort study. Intelligence, 29, 389–399.

[bates-9] Bates, T. C., & Stough, C. (1998). Improved Reaction Time Method, Information Processing Speed, and Intelligence. Intelligence, 26(1), 53-62.

[10] Demetriou, A., Mouyi, A., & Spanoudis, G. (2008). Modeling the structure and development of g. Intelligence, 5, 437-454.

[11] Demetriou, A., Mouyi, A., & Spanoudis, G. (2010). The development of mental processing. Nesselroade, J. R. (2010). Methods in the study of life-span human development: Issues and answers. In W. F. Overton (Ed.), Biology, cognition and methods across the life-span. Volume 1 of the Handbook of life-span development (pp. 36-55), Editor-in-chief: R. M. Lerner. Hoboken, NJ: Wiley.

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