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Classic experiments explained

Stop Signal Delay Task

In short

The Stop Signal Delay task (SSD), first developed by Logan and Cowan in 1984, is designed to assess participants' inhibitory control. It is often used as a clinical research tool to test disorders such as ADHD and schizophrenia. The task measures response inhibition, as participants are instructed to respond to a cue on a screen in particular time frame, but control and stop their response when a stop signal appears.


There are many different versions of the SSD task. The sample built in Gorilla involves an arrow pointed to either the left or the right. If the arrow points to the left, the participant will press the F key, if the arrow is pointing to the right, the J key. The participant is asked to respond quickly (within half a second). After the initial training phase, a red cross may be presented, and this is the participant’s stop signal, so they should not press anything.

A gif of the Stop Signal Delay task from the participant's perspective. An arrow appears on the screen, sometimes followed by a red cross. Participants receive feedback via a thumbs up or thumbs down icon.

What does the SSD task investigate?

The ability to suppress unwanted action or impulses, as tested by SSD tasks, is a vital component of goal directed, controlled and flexible behaviour. SSD tasks are functional tools that are used in psychology, psychiatry and neuroscience and can be used to assess both humans and non-humans, such as primates and rodents.

SSD research protocols demonstrate a link between participants' inhibitory control capacity and a range of mental health disorders. A shorter stop-signal reaction-time (SSRT) indicates efficient response inhibition.

The horse race model

The horse race model, in the context of SSD tasks, proposes that when a signal is presented, two processes begin. There is a ‘go’ process for executing the response, as well as a ‘stop’ process for inhibiting the response, and these processes race against each other.

If the ‘go’ process wins, the response is made. If the ‘stop’ process wins, the response is inhibited. The model assists our understanding of efficiency and speed of the response inhibition mechanisms in the brain.

Can I use a SSD task in online research?

Yes, absolutely! In fact, other researchers have already used an SSD task to study the relationship between diet and psychological health (Tuck et al., 2022).

How does it work in Gorilla?

You can try out and clone our sample of an SSD task. Of course, you can also tweak this sample to fit your protocol!

Have a look: Try a Stop Signal Delay task in Gorilla

Are there any papers Gorilla users have written using SSD tasks?

Yes, there are! Have a look at the following article:

Frequency of fruit consumption and savoury snacking predict psychological health; selective mediation via cognitive failures


Carter, J. D., Farrow, M., Silberstein, R. B., Stough, C., Tucker, A., & Pipingas, A. (2003). Assessing inhibitory control: a revised approach to the stop signal task. Journal of Attention Disorders, 6(4), 153-161.

Logan, G. D., & Cowan, W. B. (1984). On the ability to inhibit thought and action: A theory of an act of control. Psychological Review, 91(3), 295.

Tuck, N. J., Farrow, C. V., & Thomas, J. M. (2023). Frequency of fruit consumption and savoury snacking predict psychological health; selective mediation via cognitive failures. British Journal of Nutrition, 129(4), 660-669.

Verbruggen, F., & Logan, G. D. (2008). Response inhibition in the stop-signal paradigm. Trends in Cognitive Sciences, 12(11), 418-424.

Verbruggen, F., & Logan, G. D. (2009). Models of response inhibition in the stop-signal and stop-change paradigms. Neuroscience & Biobehavioral Reviews, 33(5), 647-661.

Verbruggen, F., Aron, A. R., Band, G. P., Beste, C., Bissett, P. G., Brockett, A. T., ... & Boehler, C. N. (2019). A consensus guide to capturing the ability to inhibit actions and impulsive behaviors in the stop-signal task. eLife, 8, e46323.

This page was written in collaboration with Lizzie Drury