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With regards to reflexes, reaction time is the time from the onset of a stimulus until the emmission of an organism response.


  • Complex reaction time or compound reaction time is the latency between a variable stimulus and a respectively variable response.
    • Go/NoGo (also called Recognition) reaction time task in which participants respond to one particular event but ignore other events
    • Choice reaction time task in which participants respond differentially to two stimuli by pressing one key for event A and a separate key for event B
    • The Implicit Association Test, a subset of choice reaction time tasks, in which 4 types of stimuli are categorized using 2 keys.
    • Central reation time (aka abbreviated reaction time or reduced reation time) is the portion of reaction time left after subtracting the time taken for an impulse to travel between the sensory receptor and the brain and then from there to the muscle. This approach to analysis was suggested by the Dutch opthalmologist Franciscus Cornelius Donders in 1868.

At the University of New South Wales, slower reaction times has been studied as a contributing factor in falls of elderly.


The major factors affecting reaction time are:

  • Recognition
  • Choice
  • Number of stimulii
  • Type of stimulus
  • Stimulus intensity
  • Diseases, such as chicken pox
  • Distractions
  • Fatigue
  • Poor vision

There are many other factors that can also affect reaction time:

  • Practice and error
  • Gender
  • Age
  • Race (Tubman, 1993)
  • Finger Tremors (Brebner and Welford, 1980)
  • Right vs. left hand (Dane and Erzurumluoğlu, 2003)
  • Vision (Direct vs. Peripheral) (Brebner and Welford, 1980)
  • Sobriety
  • Breathing Cycle (Buchsbaum and Calloway, 1965)
  • Stimulant Drugs (Caffeine) (Lorist and Snel, 1997)
  • Psychological Stability

History of the field

Physical scientists such as Archimedes and philosophers such as Aristotle conducted many observations involving aspects of chronometric measurement; however the tools or impetus to measure cognitive reaction time apparently was not developed, or simply has not left a significant traceable thread in the literature. The literature in other fields, e.g., epigraphical evidence, remnants of papyri, sherds, and other source material is uncertain and warrants additional investigation. An understanding of physical reaction time is critical for fields such as ballistics, archery, athletics and the physical sciences in order to estimate and measure.

Abū Rayhān al-Bīrūnī was the first to describe the concept of reaction time:[1]

"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."

Franciscus Donders was among the first to systematically analyze human RT to measure the duration of mental operations.

Methods of assessment


See also


  1. Iqbal, Muhammad, "The Spirit of Muslim Culture", The Reconstruction of Religious Thought in Islam,, retrieved on 2008-01-25 

Jensen, A. R. (1993). Spearman's hypothesis tested with chronometric information processing tasks. Intelligence 17: 47–77. Andrew Roddam - King's Baptist Grammar School

External links

Simple Reaction Time:

Complex Reaction Time:

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