Protocol - Inhibitory Control (Stop Signal Paradigm)

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STOP-IT is a computer-administered stop-signal task. Participants react as quickly as possible to a visual stimulus unless it is followed by an auditory stop signal presented after a variable delay. STOP-IT includes an analysis module (ANALYZE-IT) that calculates several summary variables.

For more conceptual information about the stop-signal task, please refer to the entry for the Stop-signal task in the Cognitive Atlas: http://www.cognitiveatlas.org/term/stop_signal_task

Specific Instructions

A compilation of research that has utilized this program can be found at www.psy.vanderbilt.edu/faculty/logan/#stopit

The task itself as compiled executable code for Windows 2k/XP can be downloaded from https://ore.exeter.ac.uk/repository/handle/10871/13860




Summary of the STOP-IT Stop Signal Task

The stop-signal procedure consists of a visually based primary task, followed 25 percent of the time by an auditory-based stop signal. For the primary task, participants differentiate between a square or circle by pressing a specific key as quickly as possible. The visual cues remain on the screen until the participants respond or 1,250 milliseconds (msec) expire. For the stop-signal task, the visual cue is followed, after a variable length of time (initially 250 msec), by a tone that signals to the subject not to respond. If the participant successfully inhibits their response, the stop-signal delay increases by 50 msec. If the participant does not successfully inhibit their response, the stop-signal delay decreases by 50 msec.

STOP-IT includes a practice phase of 32 trials followed by an experimental phase of three blocks of 64 trials (total). The number of practice and experimental phase trials can be adjusted.


Results are written to an output file that includes block number, trial number, type of trial, whether the response was correct, reaction time, and stop signal delay. The ANALYZE-IT software calculates the means for a variety of summary variables including an estimation of stop signal reaction time (SSRT), where longer stop signal reaction time indicates greater motor impulsivity.

Personnel and Training Required

STOP-IT can be administered by research assistants trained in the ethical and competent use of psychological tests.

Equipment Needs

STOP-IT can be installed on computers running Windows 2000/XP.

Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Self-administered evaluation


Child, Adolescent, Adult


Adults, adolescents, and children aged 7 years or older

Selection Rationale

The stop-signal task is a well-established, validated test of inhibitory control. STOP-IT is a freely available, precompiled executable program to perform the stop-signal task, which does not require further programming by the investigator.



Human Phenotype Ontology Cognitive impairment HP:0100543 HPO
Human Phenotype Ontology Addictive behavior HP:0030858 HPO
Human Phenotype Ontology Impulsivity HP:0100710 HPO
Human Phenotype Ontology Disinhibition HP:0000734 HPO
caDSR Form PhenX PX530402 - Inhibitory Control Stop Signal Paradigm 6930461 caDSR Form
Derived Variables


Process and Review

The Expert Review Panel #3 (ERP 3) reviewed the measures in Alcohol, Tobacco and Other Substances, and Substance Abuse and Addiction domains.

Guidance from ERP 3 includes:

• Changed name of Measure

• Updated protocol

• New Data Dictionary

Back-compatible: Back-compatible: Partially back-compatible (updated/similar protocol which would require some changes to the data dictionary), variable mapping between current and previous protocols can be found here.

Previous version in Toolkit archive (link)

Protocol Name from Source

STOP-IT task


Verbruggen, F., Logan, G. D., & Stevens, M. A. (2008). STOP-IT: Windows executable software for the stop-signal paradigm. Behavior Research Methods, 40, 479-483.

Executables for the STOP-IT task and the accompanying ANALYZE-IT analysis program can be downloaded from Frederick Verbruggen’s website (Department of Psychology, University of Exeter, UK).

General References

Boucher, L., Palmeri, T. J., Logan, G. D., & Schall, J. D. (2007). Inhibitory control in mind and brain: An interactive race model of countermanding saccades. Psychological Review, 114, 376-397.

Monterosso, J. R., Aron, A. R., Cordova, X., Xu, J. S., & London, E. D. (2005). Deficits in response inhibition associated with chronic methamphetamine abuse. Drug and Alcohol Dependence, 79, 273-277.

Nigg, J. T., Wong, M. M., Martel, M. M., Jester, J. M., Puttler, L. I., Glass, J. M., Adams, K. M., Fitzgerald, H. E., & Zucker, R. A. (2006). Poor response inhibition as a predictor of problem drinking and illicit drug use in adolescents at risk for alcoholism and other substance use disorders. Journal of the American Academy of Child and Adolescent Psychiatry, 45, 468-475.

van den Wildenberg, W. P. M., & van der Molen, M. W. (2004). Developmental trends in simple and selective inhibition of compatible and incompatible responses. Journal of Experimental Child Psychology, 87, 201-220.

Verbruggen, F., & Logan, G. D. (2009). Models of response inhibition in the stop-signal and stop-change paradigms. Neuroscience & Biobehavioral Reviews, 33, 647-661.

Smith, J.L., Mattick, R.P., Jamadar, S.D., & Iredale, J.M. (2014). Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis. Drug and Alcohol Dependence, 145, 1-33.

Protocol ID


Export Variables
Variable Name Variable IDVariable DescriptiondbGaP Mapping
PX530402010000 What is the calculated estimation of stop more
signal reaction time? Longer stop signal reaction time indicates greater motor impulsivity. show less
Substance Use-related Neurobehavioral and Cognitive Risk Factors
Measure Name

Inhibitory Control (Stop Signal Paradigm)

Release Date

November 21, 2016


This measure assesses the ability of the participant to inhibit a response that has already been initiated.


Inhibitory control is a component of impulsivity, and poor response inhibition is a risk factor for substance use disorders (Monterosso et al., 2005; Nigg et al., 2006).


adolescent, Adult, Child, impulsivity, Inhibitory Control, STOP-IT, Stop-Signal, Stop-signal Paradigm, Stop-Signal Task, substance abuse, substance use, Vanderbilt University, SAA, Substance Use-related Neurobehavioral and Cognitive Risk Factors, computer administered

Measure Protocols
Protocol ID Protocol Name
530402 Inhibitory Control (Stop Signal Paradigm)

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