Cognition Laboratory Experiments

John H. Krantz, Hanover College,






Mental Imagery


Decision Making


Statistical Concepts

Hanover College
Psychology Department

Instructions for the
Brown-Peterson Experiment

In this experiment, you can experience a dual task situation.  In many real world situations people are required to monitor or pay attention to more than one task at a time.  For example, while driving you have to both monitor your position on the road and monitor your speed.  Psychologists study our ability to do two things at once in the dual task experiments.  In this version of a dual task experiment, there is a primary tracking task where you will try to keep a dot inside of a box, sort of like following the road.  During this tracking task, letters appear and if a target letter (X) appears you have to respond to it by clicking the mouse.  You can manipulate the features of both the primary and secondary tasks to see how they impact your ability to do both successfully. 


Variable Settings
Number of Trials Per level The number of trials in each delay level from 5 to 100
  Variables for the Memory task
Type of Stimulus Choose either a three consonant trigram (CCC) or a consonant-vowell-consonant trigram (CVC)
Duration of the letters How long the letters and the number to count backwards from will be shown.
Minimum Duration The shortest time you wish to do the distraction before recall (0 to 10 seconds)
Maximum Duration The longest time period for the distraction task before recall (10 to 45 seconds)
Number of Distractions The number of intervals to test (3 to 10). Equal interval steps between the minimum and maximum will be determined.
  Variables for the distraction task
Range angle varies The range that the direction of the motion of the dot to be tracked can change with each update from 0 to 360.  The smaller the angle variation, the more direct the movement of the dot and thus easier to follow.  The larger the angle variation the more random the movement of the dot.
Speed of Dot How fast the dot moves (pixels per update, from 1 to 50)
Size of dot to track The diameter of the dot (in pixels, from 1 to 20).
Size of target box The size of the target box that you must keep the dot in during tracking (in pixels, from 2 to 200).
Use Tone Use a tone to give the rate of counting backwards by 3
Rate The time between tones.

After you have finished making your settings, press the Done button at the bottom of the screen. The Brown-Peterson task window will open. Start the trial by pressing the space bar. You will be presented a trigram to remember and a three digit number. After these items are removed you will go to the distraction task. It is very important that you engage fully in the distraction task. There are two tasks you are to do simultaneously. First, track the dot by moving, not dragging, your mouse over the screen. Second, from the three digit number count backwards outloud by three. There will be beeps that you should try to keep up with. If you cannot keep up, just go as fast as possible. If you lose track or your number, please just pick a new number and keep going. When the fixation mark returns, type the letters from the trigram. They will appear at the bottom of the screen. Press the space bar to go to the next trial.

At the end of the experiment your results will be presented.  You will be shown the proporition of letters you typed in the correct position in the trigram for each delay interval you tested. You can get your responses for each trial by clicking on the Trial Data button at the bottom of the screen.

Click here to start the experiment.


Brown, J. (1958). Some tests of the decay theory of immediate memory. The Quarterly Journal of Experimental Psychology, 1012-21.

Peterson, L., & Peterson, M. (1959). Short-term retention of individual verbal items. Journal of Experimental Psychology, 58(3), 193-198.