Presentation of Select Stimuli from a List

Good afternoon,

I am currently creating a memory experiment in which participants are required to recall the location and order of stimuli (.jpg images) as they are presented on the screen. The task is meant to be adaptive, meaning the difficulty increases (adding more stimuli to be remembered) when the participant performs well and decreases (reducing number of stimuli to be remembered) when the participant fails to recall a sequence correctly.

I’ve created a stimulus list containing all of my 15 possible stimuli to be presented, but would like to initially randomly show 3 from this list at the beginning of the experiment, then have the program increase and decrease (by one) the number of stimuli randomly pulled from the list, depending on the participant’s performance.

When I randomize and present stimuli from a list, it presents all 15 stimuli successively. How do I program the task to only show 3 of these stimuli initially from the list of 15? In addition, how do I then make this list adaptive to the participant’s performance?

Thank you for your time,


For increasing and decreasing the level of difficulty, the basic approach would be to use the parameters feature, create two of type “Counter”:

  • Let’s call the first one “Number of Stimuli Presented”. It keeps track of how many stimuli you have presented, where one stimulus is really one trial.
  • We can call the second one "Maximum Stimuli to Present". In the Parameters dialog, you can give it an initial value of 3, and a minimum/maximum of 1 and 15, like this:

You would then compare these two counters in the Trial Editor’s When to Run tab and allow more presentations only if “Number of Stimuli Presented” is less than “Maximum Stimuli to Present”.

Elsewhere in the experiment where the participant responds, you can then increment or decrement the “Maximum Stimuli to Present” counter depending on the correctness of the response.

Thank you for your help with this issue! I have done as you suggested, as I have created both counters and applied them comparatively in the Trial Editor window corresponding with the stimulus list; however, when I randomize the trials through List Access and run the experiment, all 15 stimuli are still presented before the recall page. Did I miss a step? I created the counter for “Maximum Stimuli to Present” as shown, but left the “Number of Stimuli Presented” with its default settings. Could this be what is creating this issue?

Happy new year!

Can you please post the experiment? Anything that I say without seeing it would be a wild guess.