Introduction

The experiment demonstrated in this activity provides yet more proof that attention is a far scarcer commodity than we might think.

Instructions

Click the white square at left to start a trial. Half a second later, the square will fill up with 20 red and green circles. Then, between 500–1000 ms later, one of the circles will become brighter. At the same time, the color of the brightened disk may change, from red to green or from green to red. Your job at this point is to try to decide what color the probed disk was before it got brighter. Half the time the color will have changed, and half the time it will be the same. For example, a dark red disk might be replaced by a bright red disk or a bright green disk. In either case, you should click the button below the display to indicate that the disk was originally red.

Got it? If not, don’t be embarrassed—it’s a little confusing at first. Just read the above instructions over again, then click the big white square at left to start.

Trial Started...

Click one of the buttons below the stimuli to indicate whether you think the probed stimulus (the brighter one) was red or green before it got brighter.

If you're not sure, just take a guess and try again on the next trial. Or go back to the activity introduction and re-read the experiment instructions.

Results

Correct! The probed item was red, the same as the probe (no color change occurred).

Out of 10 trial(s) so far, you’ve gotten 9 (90%) correct.

Click the display to start a new trial.

What's Going On Here?

Your visual system is great at detecting everything in front of your face—for example, you can see all 20 of the circles at the start of each trial in this experiment just fine. Likewise, your memory is (despite what you might think the day after taking your final exams) pretty darn good.

But getting a stimulus from the visual processes to the memory processes requires attention, and this is where the problem lies. It’s not that your attentional processes are faulty—when you do pay attention to a visual stimulus, you’re quite good at putting all aspects of the stimulus together to form a coherent, memorable whole. (Imagine, for example, that you saw just one circle instead of 20. In that case, you would be able to accurately report the color of the circle nearly every time.) Rather, as this and many other experiments show, attentional resources are limited.

This fact leads to the notion of an attentional bottleneck. If you happen to be looking at the circle that changes brightness at the exact time the change occurs, the circle will be likely to make it through the bottleneck into memory, and you will be able to say what color it was before the change. Otherwise, all you will remember is a bunch of green and red circles, and you will probably be deciding by chance what color the cued circle was before the change occurred.

Click the white square to start another trial.