TEST

Simple Reaction Time (SRT)

Perceptual-motor speed and sustained alertness

“See and react.” The most basic test of sensorimotor processing. Sensitive to states of generalized slowing, mild cognitive impairment, and alterations of the central or peripheral nervous system.

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ms

PRECISION

1

TARGET STIMULUS

~310

REFERENCE MS

7

INDICATORS

WHAT THE TEST IS

Pure sensory control

Inspired by classic simple reaction time tasks (CTIP, Reicker et al. 2007) and implements the sensory control level proposed by Koechlin and Summerfield (2007).

It measures simple perceptual, motor, and sustained alertness processes (Jensen, 2006). The subject’s RT comprises the time needed for sensory transduction, neural transmission of the stimulus to the brain, and neural transmission to the muscles. For this reason, many studies use it as a reference or control measure for more complex processing speed tasks.

Its reliability is high: it shows practically no practice effect after the first 10 trials (Teichner & Krebs, 1974).

HOW IT IS ADMINISTERED

Press as soon as the circle appears

The user must press the space bar as soon as a white circle appears on the screen. It is the most basic “see and react” test, with no need to decide between options. The first 10 trials are used to establish the learning curve and reach maximum performance.

WHAT THE TEST MEASURES

Indicators and their interpretation

Correct responses

Total correct responses. Level of effectiveness of basic perceptual-motor processing and sustained attention.

High: adequate detection, sustained attention, effective performance.
Low: perceptual problems, attentional difficulties, fatigue, or lack of engagement.

Omissions

Occasions when no response is made to the stimulus. Reflects attentional lapses or decreased alertness.

High: attentional lapses, disconnection, fluctuation.
Low: adequate maintenance of attention.

False alarms

Responses made in the absence of the target stimulus. Indicator of impulsivity or inhibitory control.

High: impulsivity, inhibitory control deficit.
Low: good inhibitory control, adequate adjustment to the task.

RT correct responses

Mean time (ms) between stimulus onset and keypress, only for correct responses.

Slow RTs: sensorimotor slowing, fatigue, motor problems.
Fast RTs: fast and efficient processing.

RT variability

Standard deviation of RTs in correct responses. Consistency in response speed.

High: attentional lapses, fatigue, motor instability.
Low: consistent and well-regulated performance.

RT fatigue

Difference between the final 25% and the initial 25% of the task. Measures the emergence of cognitive or motor fatigue.

Increase: progressive fatigue, difficulty sustaining performance.
Stability: good endurance and sustained attention.

Speed-accuracy tradeoff

Relationship between mean RT and proportion of correct responses. Reflects the strategy adopted (speed vs. accuracy).

High: inefficient performance, bias toward speed or accuracy.
Low: optimal balance between both variables.

Learning rate

Variation in RT during the first 10 trials. Initial adaptation, activation level, and adjustment speed.

Positive: initial adjustment difficulty or early fatigue.
Negative/zero: rapid adaptation or normal “warm-up” period.

REFERENCES

Bibliography

Reicker, L. I., Tombaugh, T. N., Walker, L., & Freedman, M. S. (2007). Reaction time: An alternative method for assessing the effects of multiple sclerosis on information processing speed. Archives of Clinical Neuropsychology.
Jensen, A. R. (2006). Clocking the mind: Mental chronometry and individual differences. Elsevier.
Koechlin, E., & Summerfield, C. (2007). An information theoretical approach to prefrontal executive function. Trends in Cognitive Sciences.
Tombaugh, T. N., Rees, L., Stormer, P., Harrison, A. G., & Smith, A. (2010). The effects of mild and severe traumatic brain injury on speed of information processing. Archives of Clinical Neuropsychology.
Teichner, W. H., & Krebs, M. J. (1974). Laws of visual choice reaction time. Psychological Review.