HDDM.StimCoding: I only get positive drift rates for both response options.

[Bohyun Park "Gemma"]

Hi users!

I am fitting HDDM to a flanker dataset, and I am keep getting an issue with getting positive drift rates only, despite the two equiprobable responses (i.e., "Left" and "Right").

I am using StimCoding to fit my data. Below is my code and the output. My advisor suggested that this might be because that we need to manually flip the sign for one response option versus another, but I was not entirely sure if that is the case.

Could it be possible that this may be the issue with the data structure, such that I can ONLY have absolutely necessary variables in my dataset (i.e., the variables that will be used in the model fitting process only)?

Or is it true that we need to manually flip the sign for one responses option versus the other? In my dataset, R and L are coded 0 and 1, respectively, and are integers (not floats).

Please let me know if you have any suggestions or advice! I would sincerely appreciate it.

Best,

Gemma

[Michael J Frank]

See below for stim coding - you need to use hddm.HDDMStimCoding. That way v will automatically be flipped for each response.

https://hddm.readthedocs.io/en/latest/howto.html

Michael 

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