The attentional blink
Test whether attending to one letter in a rapid stream leaves a brief period in which a second one goes unnoticed.
Method
Procedure
- After a cross, a stream of 18 to 23 letters appears at the centre of the screen, about ten letters each second.
- One letter is coloured orange. Remember it.
- On most streams an X appears between 1 and 8 letters after the coloured letter; on 8 of the 32 streams there is no X.
- After each stream, choose the coloured letter from four options, then say whether an X appeared after it.
Responses
- Letter keys
- choose the coloured letter (or press its button)
- J
- yes, an X appeared
- F
- no X appeared
Measures
For each delay between the coloured letter and the X, the percentage of streams on which you reported the X, counting only streams on which you identified the coloured letter correctly. The question is whether attending to the first letter leaves a short period in which a second target is easily missed.
Practice
Three practice streams, the first two shown more slowly, tell you afterwards what the coloured letter was and whether an X appeared.
Letters change about ten times each second in a small area at the centre of the screen; the screen as a whole does not flash. People who are sensitive to flickering or rapidly changing images may prefer not to take part. The coloured letter differs from the others in colour and brightness.
Terms
- Rapid serial visual presentation: Showing items one after another at the same place, here about ten letters a second.
- First and second target: The coloured letter is the first target; the X is the second.
- Lag: How many letters after the first target the second one appears; at about 100 ms per letter, lag 3 is about 300 ms.
- Attentional blink: A short period after the first target during which the second target is often missed.
- Working memory: The system that holds information in mind for a few seconds; the first target must be stored there to be reported.
Experiment
Responses stay in this browser tab. Nothing is stored or sent, and everything is lost when the page is closed or reloaded.
Results
Interpretation
The shape of the line in the chart is the main result. A dip in detection a few hundred milliseconds after the coloured letter, with better detection later, indicates an attentional blink. Detection immediately after the coloured letter (lag 1) is often good, as if the X were processed together with it. If an X was reported on many streams that had none, some reports were guesses and the percentages overstate detection.
Comparison with published studies
In the original study, an X was poorly detected when it appeared between about 180 and 450 ms after the target letter (Raymond, Shapiro and Arnell, 1992). Lowest detection in roughly this range follows the same pattern.
Limitations
There are only three streams at each delay, so each point on the chart can take only a few values (0%, 33%, 67% or 100%, or fewer if the coloured letter was missed). The display timing depends on the screen refresh rate; streams with irregular timing are left out.
The result comes from one person in one session, on a device whose timing and display are not calibrated. It describes this run, not a stable characteristic of the participant, and a second run could differ by chance alone. Research studies test many participants under controlled conditions and report the average with its variability. The experiment is educational; it is not a test of ability or health.
One row per stream: delay of the X in letters (0 = no X), the coloured letter and the one you chose, whether an X was present and reported, the delay in ms, the measured duration of each letter and whether the stream was used. In the file, 1 means yes and 0 means no. The file is created on this device and can be opened in a spreadsheet.
Background
Original findings
Raymond, Shapiro and Arnell (1992) presented letters in rapid succession at the same place. When participants had to identify a target letter, a following X was poorly detected if it appeared during an interval of about 270 ms beginning about 180 ms after the target, whereas an X immediately after the target, or later, was detected accurately. When participants did not have to identify the target, there was no such deficit. They called it an attentional blink. Detection of the X is usually analysed only on trials on which the coloured letter was identified correctly, as here.
Neural basis
The blink is often explained by a limited capacity for selecting an item and consolidating it in working memory: while the first target is being processed, a second one that follows soon after is more likely to be lost, although it may still be processed to some extent without being reported. Brain-imaging and EEG studies have linked these processes to regions of the frontal and parietal cortex, but the details are still debated.
References
- Raymond, J. E., Shapiro, K. L., & Arnell, K. M. (1992). Temporary suppression of visual processing in an RSVP task: an attentional blink? Journal of Experimental Psychology: Human Perception and Performance, 18(3), 849–860. https://doi.org/10.1037/0096-1523.18.3.849
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