non-random selection of stimuli


non-random selection of stimuli

Author
Message
Georgia
Georgia
Expert
Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)

Group: Forum Members
Posts: 9, Visits: 49
Hello,
I am new to inquisit and have just learned how to program a full task myself. I would like to be able to program a non-random selection of stimuli that reflects specific probabilities, but as far as I can tell there is the 'noreplace' or the 'noreplacenorepeat' option which randomly selects stimuli either with or without repeating. Is there any way to program a particular probability of a certain stimulus being presented for each trial or each block of trials?
The only other option I see is to hand-code my blocks to create the probabilities myself. As an example, I've pasted code below for the following: 70% chance of seeing stimulus 1, 10% chance of seeing stimulus 2, 10% chance of seeing stimulus 3, and 10% chance of seeing stimulus 4. Basically 7/10 trials are stimulus 1 and the rest are stimuli 2-4. My syntax seems to be wrong so I am wondering if this is even possible to do. 

<block practice>
/trials = [1=stimulus1; 2=stimulus2; 3=stimulus4; 4=stimulus1; 5=stimulus3; 6=stimulus1; 7=stimulus1; 8=stimulus1; 9=stimulus1; 10=stimulus1]
/pretrialpause = 500
</block>

Any help would be much appreciated!

Thanks,
Georgia



Dave
Dave
Supreme Being
Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)Supreme Being (679K reputation)

Group: Administrators
Posts: 9.8K, Visits: 46K
What matters with trial selection via the <block> element's /trials attribute is the *proportions you enter into the pool*. For example

/ trials = [1-6=noreplace(a,b)]

will sample randomly (without replacement) <trial a> and <trial b> in *equal proportions* / a 1:1 ratio. You'll end up with exactly 3 "a"-trials and 3 "b"-trials in random order. With

/ trials = [1-6=noreplace(a,a,b)]

the ratio is 2:1, i.e., you'll end up with 4 "a"-trials and 2 "b"-trials in random order. As to your own task, what you'll want to do is thus:

/ trials = [1-10=noreplace(stimulus1, stimulus1, stimulus1, stimulus1, stimulus1, stimulus1, stimulus1, stimulus2, stimulus3, stimulus4)]

Georgia
Georgia
Expert
Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)Expert (1.4K reputation)

Group: Forum Members
Posts: 9, Visits: 49
Thanks, this really helped!

Georgia
GO


Reading This Topic


Login
Existing Account
Email Address:


Password:


Social Logins

Select a Forum....






Millisecond Forums


Search