Go / No-Go
A shape flashes on screen. Click for green circles, resist clicking for red squares. Tests impulse control.
This task measures response inhibition: the ability to suppress a prepotent response. It's a core measure of executive function used in ADHD research.
d-prime combines your hit rate and false alarm rate into a single sensitivity score, separating true ability from response bias.
| 😴 | Sleep | Sleep deprivation increases false alarms dramatically. |
| 🍷 | Alcohol | Even small amounts impair inhibition control. |
| 🏃 | Exercise | Acute exercise improves inhibitory control. |
| ⏰ | Time of Day | Inhibition is strongest in the morning hours. |
What Does the Go/No-Go Test Measure?
This test measures response inhibition — the ability of your prefrontal cortex to suppress a prepared motor action when you recognize that acting would be inappropriate. When a Go signal (green circle) appears, you click as fast as possible. When a No-Go signal (red square) appears, you must override the reflex to click. The difficulty is that Go trials are more frequent, so clicking becomes habitual — making suppression on No-Go trials genuinely effortful.
Your score is reported as d-prime (d’), a signal detection theory metric that combines your hit rate (Go accuracy) and false alarm rate (No-Go errors) into a single sensitivity index. High d’ means you’re fast on Go trials and accurate on No-Go trials simultaneously — the key tradeoff the test is designed to probe.
How This Test Works
20 trials are presented at random intervals. Approximately 70% are Go trials (green circles), 30% are No-Go trials (red squares). The ratio is set to create a strong prepotent response — after many Go trials, your motor system expects to click, making No-Go suppression harder. Each trial shows for a limited duration; a missed Go trial (no click during the window) is a miss. A clicked No-Go trial is a false alarm.
Your d’ score is computed from the hit rate and false alarm rate using standard signal detection formulas. A score of 0 means you’re performing at chance. A score of 3.0+ means you’re detecting signals with near-perfect accuracy while avoiding noise.
Why Inhibitory Control Matters
- Everyday safety: Response inhibition is what stops you from reaching for your phone while driving, stepping into traffic before checking, or blurting something out in a meeting. It’s a practical safety function that operates dozens of times a day.
- Clinical relevance: Elevated false alarm rates are a hallmark of ADHD (particularly the hyperactive-impulsive subtype) and are used in clinical settings as part of continuous performance task (CPT) batteries. This is not a diagnostic tool, but the same neurocognitive mechanism it measures is the one that’s disrupted in ADHD.
- Substance effects: Even moderate alcohol consumption measurably increases false alarm rates before it affects Go reaction time — inhibitory control is one of the most sensitive functions to impairment.
- Sports: Athletes in sports requiring split-second decisions about when not to act (tennis players holding a forced shot, defenders avoiding a feint) benefit from high inhibitory control scores.
Inhibitory control and reaction speed are related but distinct. Your Go RT on this test reflects the same processing chain as the Reaction Time Test, but with an additional classification layer. Try our Sustained Attention Test to measure your vigilance endurance over a longer period.
Go/No-Go Benchmarks by Percentile
d’ (d-prime) scores. Higher is better. A d’ of 0 is chance performance; 4.65 is theoretically perfect.
| Percentile | d’ Score | Classification | Typical Profile |
|---|---|---|---|
| Top 10% | ≥ 3.0 | Exceptional | Athletes, high executive function |
| Top 25% | 2.2–3.0 | Good | Well-rested, high-focus state |
| Median (50th) | ~1.7 | Average | Most healthy adults |
| Bottom 25% | 1.0–1.5 | Developing | Fatigue, distraction, high impulsivity |
| Bottom 10% | < 1.0 | Impaired | Sleep-deprived, alcohol, significant inhibition difficulty |
Frequently Asked Questions
What is response inhibition, and why does it matter?
Response inhibition is the prefrontal cortex’s ability to cancel a prepared motor command. It’s governed by the right inferior frontal gyrus and the pre-supplementary motor area. When a No-Go signal is detected, this system fires a rapid “stop signal” that must arrive at the motor cortex before the action is executed. If it arrives too late, a false alarm occurs. The speed of this stop signal is called the Stop Signal Reaction Time (SSRT) — a key measure in clinical inhibition research.
How is this test used in ADHD screening?
Continuous performance tasks (CPT) that follow the Go/No-Go structure are used in clinical neuropsychology as part of ADHD assessment batteries. People with ADHD-predominantly hyperactive presentation typically show normal or faster-than-average Go reaction times, but significantly higher false alarm rates. This pattern reflects impulsive motor release rather than inattention. This test is not a diagnostic instrument, but tracking your false alarm rate over time is genuinely informative.
Does fatigue affect false alarms more than reaction speed?
Yes. Sleep deprivation and cognitive fatigue impair the prefrontal cortex disproportionately compared to more automatic visual processing. A tired person’s Go reaction time may only slow by 20–30ms, but their false alarm rate can triple. This is why surgeons, pilots, and air traffic controllers have strict rest requirements — inhibitory control degrades well before gross reaction speed does.
What is d-prime (d’) and why is it better than just counting errors?
d’ separates your true signal detection ability from your response bias. A person who clicks on everything will have a perfect hit rate but many false alarms — which raw accuracy doesn’t penalize fairly. d’ accounts for both simultaneously: a high d’ means you’re correctly distinguishing Go from No-Go, regardless of how liberal or conservative your clicking strategy is.
Can inhibitory control be trained?
To a moderate degree. Response inhibition responds to mindfulness training, structured cognitive control exercises, and certain aerobic exercise protocols. The effects are modest compared to the improvements seen in motor memory tasks, but they are real and measurable. The most impactful single factor remains sleep quality — a well-rested prefrontal cortex outperforms a fatigued one regardless of training history.