equal distribution of trial types before and after a break

[karmacoma]

Hi Jeremy,

In my experiment I have 30 congruent and 30 incongruent trials, and there is a break in the middle (i.e. after 30 trials). Is there a way to pseudorandomize the stimuli such that there are precisely 15 congruent and 15 incongruent trials presented before and after the break?

Thanks a lot!

[Jeremy]

Hi,

You can use the pick function, defined in this post:

congruent = randomize("congruent");
incongruent = randomize("incongruent");

Sequence(
  rshuffle(pick(congruent,15),pick(incongruent,15))
  ,
  "break"
  ,
  rshuffle(pick(congruent,15),pick(incongruent,15))
)

Let me know if you have questions

Jeremy

[karmacoma]

Thanks Jeremy, that works for me! However, the pattern of presentation is fixed (e.g. con-incon-con-incon-con-incon…) – do you know how to make the con/incongruent trials more randomly distributed?

[Jeremy]

Yes, replace rshuffle( ... , ... ) with randomize(seq( ... , ... ))

Jeremy

[karmacoma]

Thank you, that works perfectly!

[Author]

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