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About this tool
Experience the famous Gorilla Experiment — test your awareness, see if you spot the unexpected, and share your results.
The Inattentional Blindness Test recreates the selective-attention task from Simons and Chabris's 1999 "invisible gorilla" study: six animated players, three in white and three in black, pass two balls around while you silently count only the white team's passes. Partway through, a gorilla walks across the screen, and afterwards you are asked both for your pass count and whether you saw anything unusual. About half the observers in the original experiment missed the gorilla entirely, which is the point of the demonstration rather than a trick.
Open Inattentional Blindness Test on AltFTool — it loads instantly in your browser.
Pick Easy, Normal or Hard — a 45, 30 or 20 second run, with a pass every 2, 1.5 or 1 second.
Press Start the Experiment, then I'm Ready — Start!, and count only the WHITE team's passes in your head with no writing.
Answer How many passes did WHITE team make? and Did you see anything unusual?, then hit See Results & Share to compare your count with the real total.
Easy runs 45 seconds with a pass every 2 seconds and a gorilla on screen for 10; hard runs 20 seconds with a pass every second and a gorilla visible for only 3.
On normal and hard the gorilla's entry time and side of the screen vary between runs, so knowing the format does not tell you when or where to look.
Your pass estimate is checked against the real count, so you can see whether staying focused enough to count accurately is what cost you the gorilla.
It is a 1999 selective-attention study by Daniel Simons and Christopher Chabris in which viewers counted basketball passes between players in white shirts while a person in a gorilla suit walked through the scene. Around half of viewers never noticed the gorilla, demonstrating inattentional blindness: focused attention on one task can make an unexpected but plainly visible object go unregistered.
Only the passes made by the white team, keeping the count in your head with no writing. Two balls are in play at once and the black team is passing on a slightly offset schedule, which is what makes the counting demanding enough for the effect to appear.
Being within 2 of the real total is graded Excellent and within 4 is Good; beyond that the tool says the count needs work. The exact number matters less than the effort, since it is the effort of counting that produces the blindness.
No. Missing it is the ordinary result — roughly half of participants in the original study did — and it reflects how selective attention works in everyone, not a deficit. This is a demonstration for interest and teaching, not a diagnostic test; talk to a clinician about any genuine concern regarding attention.