Loading page
About this tool
Measure your sustained attention and impulsivity with a scientific Continuous Performance Task (CPT).
The Attention Span Test runs an A-not-X Continuous Performance Task in the browser: single letters flash for 250 ms every 1.25 seconds and you press the spacebar for every letter except X, which appears on roughly 15% of trials. It is built for anyone who wants a repeatable, timed measure of sustained attention rather than a personality-style quiz — students checking focus before study blocks, shift workers gauging fatigue, or people curious how their vigilance holds up over minutes. You pick a 1-, 2- or 5-minute run and finish with accuracy, average reaction time, omission errors and commission errors broken out separately.
Open Attention Span Test on AltFTool — it loads instantly in your browser.
Read the Instructions card — letters flash on screen and you press the Spacebar for every letter EXCEPT the letter X — then choose from the Test Duration menu: 1 Minute (Quick check), 2 Minutes (Standard) or 5 Minutes (Deep evaluation).
Click the 'Start Test' button to begin. After a one-second lead-in a letter appears every 1.25 seconds and stays on screen for 250ms, with about 15% of them an X, while the banner reads 'Test in progress... Stay focused.' and a SPACE key is drawn below the stimulus box.
When the run finishes you get Attention Grade: Excellent, Average or Below Average, with Accuracy as a percentage and Avg Reaction in ms, plus cards for Omission Errors (Inattention), Commission Errors (Impulsivity) and Reaction Time. Retake Test returns you to the duration screen.
Missed letters are counted as omission errors and spacebar presses on X as commission errors, so inattention and poor impulse control show up as two different numbers rather than one blended score.
Reaction time is measured with performance.now() from the exact frame the letter is painted, so results are not rounded to the nearest animation tick or network round trip.
The 5-minute option runs about 240 trials, which is where vigilance decrement typically appears — a 1-minute check is too short for attention to drift.
A Continuous Performance Task is a timed vigilance test where you respond to a fast stream of stimuli and withhold your response for one specific target. This tool uses the A-not-X variant: press the spacebar for every letter, hold back on X. The withholding is the hard part, and it is what makes the task measure inhibitory control as well as attention.
Under 400 ms is flagged as a strong result here, 400-600 ms is treated as typical, and above 600 ms is flagged for review. Simple visual reaction times in healthy adults commonly land in the 250-450 ms range, so most people who are rested and undistracted finish somewhere in the middle band.
The grade comes from two thresholds: 90% or better accuracy on non-X letters with no more than 2 presses on X scores Excellent, and accuracy below 80% or more than 5 presses on X scores Below Average. Everything in between is graded Average. Accuracy is hits divided by the number of non-X trials.
No. This is an informational self-check, not a clinical instrument — it is not normed against an age-matched population and a single browser session cannot control for screen lag, caffeine, sleep or distraction. Clinical CPTs are administered and interpreted alongside history and rating scales, so bring any concerns to a qualified clinician.