Change Blindness Test: What Are You Not Seeing?
Change blindness is one of the most unsettling findings in attention research: a large, obvious change to a scene can be completely invisible to you if your attention isn't pointed at it. This test uses the classic flicker paradigm — two versions of a scene alternate with a brief blank between them, and one item keeps changing. It usually takes far longer to find than you would expect, and that gap between expectation and reality is the point.
A quiet round of Change Blindness Test — Basic. When you start, everything else fades — just you and the task.
No sign-up needed. Press Esc to exit anytime.
Tip
Divide the field and hold one region. The blank frame exists to wipe out the motion signal that would otherwise give the change away instantly, which leaves you doing a memory comparison. That only works a region at a time: take a quarter of the field, hold it across the flicker, clear it, then move on.
Everything here is free
Every test, every difficulty, no limit and no account. If it is useful to you, you can chip in — entirely optional, and nothing changes either way.
Change Blindness Test: what it is and where it comes from
What is change blindness? The change blindness test uses the flicker paradigm of Rensink, O'Regan and Clark (1997): two versions of a scene alternate with a brief blank between them, and you find what changed. It shows how much of a scene goes unnoticed until attention lands on it. Focani's free browser version runs 4 scenes per session and needs no sign-up.
| Specification | Change Blindness Test |
|---|---|
| Primary cognitive domain | Change awareness — in the “Keeping up with change” group |
| Original citation | Rensink, R. A., O'Regan, J. K., & Clark, J. J. (1997). To see or not to see: The need for attention to perceive changes in scenes. Psychological Science, 8(5), 368–373.doi:10.1111/j.1467-9280.1997.tb00427.x |
| Core dependent metrics | Completion time (s) · Hits · False alarms (commission errors) · Misses (omission errors) |
| Standard stimulus / trial parameters | Photographs of real scenes, with the number of alternations needed to spot the change as the measure. |
| This version | Basic — 4 scenes · Dense — 5 scenes |
| Browser adaptation notes | Generated displays rather than photographs. The demonstration works — the effect is robust — but difficulty is not comparable to the published scenes. |
Full sources for every test, and what each version changes, are on the instructors page.
How to play
- A field of colored shapes appears, then blanks, then reappears slightly different.
- One item changes color on every flip. Everything else stays put.
- Tap the item you think is changing. Wrong taps count against you.
- Finish all rounds to see how long each one took you.
Change Blindness Test tips
Ways to play it better — each one comes from how this version actually scores, not from general advice about concentration.
Divide the field and hold one region
The blank frame exists to wipe out the motion signal that would otherwise give the change away instantly, which leaves you doing a memory comparison. That only works a region at a time: take a quarter of the field, hold it across the flicker, clear it, then move on.
Only color changes — nothing moves
One item changes color and everything else stays exactly where it is, so there is no point watching for movement. Color is resolved poorly away from the center of vision, which means a wide passive gaze will not catch it — the region you are looking at is the region you can actually check.
A wrong tap costs nearly a whole round
Accuracy counts the rounds you solved against the rounds plus every wrong tap, so a hopeful guess at a plausible item comes close to giving up a round outright. If nothing in the region you are holding has changed, move to the next region rather than to a guess.
One caveat worth knowing: a change of strategy moves your score for reasons that have nothing to do with attention. Your dashboard reads each session against your own recent ones, so if you adopt something from this list, give it a few sessions before reading anything into the trend.
Frequently asked questions
What is change blindness?+
The failure to notice a change to a visual scene when the change coincides with a visual disruption — a blink, a cut in a film, or the blank frame used here. Attention has to be on the right place at the right time, and when it isn't, the change simply doesn't register.
Why is there a blank flash between the two versions?+
That blank is what makes the test work. If the two versions swapped directly, the change would create a local motion signal that grabs your attention automatically and you'd spot it instantly. Blanking the whole field creates that signal everywhere at once, which cancels the shortcut and forces you to search deliberately.
Is this the same as a spot the difference game?+
The mechanic is related, but the setup is doing something different. Spot-the-difference shows both images side by side, so it's a comparison task you can work at your own pace. The flicker paradigm never lets you see both at once, so you have to hold one version in mind and check it against the other region by region — which is what exposes change blindness.
Is change blindness the same as change detection?+
No, and the two get confused constantly. Change detection tasks in the Luck & Vogel tradition measure visual working memory capacity — how many items you can hold at once. Change blindness is about attention failing to reach the changing region in the first place. Similar names, different constructs.
Where this fits
- Attention Span Test — Where attention isn't. A large, obvious change is invisible if your attention is elsewhere — usually far longer than people expect.
- Mind Wandering — A direct demonstration that attention has to be in the right place at the right time — and that it usually isn't.
Related attention paradigms
Keeping up with change — closest to this one
- Multiple Object Tracking — practices and measures divided and sustained visual attention.
- Task Switching Test — practices and measures cognitive flexibility and rule switching.