Cognitive Psychology · Simplified
Attentional Blink
Find one thing in a fast stream and, for the next few hundred milliseconds, you will miss the next one entirely.
Before you start
Two things to find in each stream
Letters appear one at a time in the middle of the panel. Somewhere in each stream there is one digit, and somewhere after it there may or may not be the letter X. After each stream you answer two questions: was the digit odd or even, and did you see an X.
Please read this before starting. In the scored block the letters change ten times a second. The panel background never changes and nothing flashes or moves, but that is still rapid visual change in one spot for about two seconds at a time. If rapid visual change is something you avoid, use Show me a worked example instead below: it produces the same figure from simulated data, clearly labelled as simulated, and you will not miss anything the activity is trying to teach.
Was the digit odd or even?
Did you see an X?
The lag function
The dip
Each point is how often you spotted the X when it arrived that many items after the digit, counting only streams where you got the digit right. One item is a tenth of a second.
All the values behind this chart
| Lag | Gap after the digit | X spotted | Streams counted |
|---|
Key idea: The X is just as visible whenever it arrives. What changes is whether anything is available to notice it. Finding the digit is not instantaneous: it occupies something for a few hundred milliseconds afterwards, and an X arriving inside that window is displayed, is looked at, and is not reported. The curve usually recovers by about half a second. The odd part is the left-hand end: an X arriving immediately after the digit is often seen perfectly well, because it is still inside the same brief window of processing that the digit opened rather than arriving after it has closed.
One person and a few streams per point, in a browser, so each point is a rough figure and the shape can easily come out ragged. Missing the X is not a failure of vision or of effort: the whole finding is that it happens to people who are trying hard and looking straight at it. Nothing here measures anyone's attention span or ability. And the name is a metaphor. Nothing closes and nothing goes dark; the eyes stay open and the stream keeps being seen.
The longer version adds a practice block with explanatory feedback on every stream, a second response mode, and a comparison across blocks. It is at Attentional Blink in the main collection.