set a fixed duration of a sequence of items

Lara94

Hi!

I am trying to understand how to set a sequence of items (e.g., stimulus display - mouse response - blank screen) that lasts always 10 seconds. This is means that, for instance, if the mouse response lasts 3 seconds, the blank screen will last 7 seconds.

Could you help me?

Thank you very much

sebastiaan

Hi @Lara94 ,

The best way to do this depends on the specifics of your experiment.

In some cases, the coroutines item will be useful because it allows you to specify a fixed duration. However, using coroutines can also make things a bit more complex than necessary.

• https://osdoc.cogsci.nl/3.3/manual/structure/coroutines/

An alternative would be to use a feedback item for the blank screen, and then use a simple Python expression to specify that the duration should be 10,000 ms minus the response time, like so:

[=10000 - var.response_time]

• https://osdoc.cogsci.nl/3.3/manual/python/about/#python-in-text-strings

You would probably also want to specify a timeout of 10,000 ms in the mouse_response .

Note that you need to use a feedback item in this case, because for a sketchpad item the duration is evaluated during the Prepare phase, so before any response is given.

• https://osdoc.cogsci.nl/3.3/manual/stimuli/visual/#sketchpad-items-are-prepared-in-advance-feedback-items-are-not

— Sebastiaan