> *c.f. your documentation: "There are two ways you can code subject
> responses (these are the values you put in the ‘response’ column in your
> data file). You can either use accuracy-coding where 1 means correct and 0
> means error, or you can use direction-coding [GB: which i understand
> meaning the same as stimulus-coded] where 1 means left and 0 means right
> ..."

> On Mon Sep 10 15:23:34 2012, Thomas Wiecki wrote:

> Hi,

> I couldn't find those passages:

> From White: "position of starting point relative to the boundaries (values
> above .5 indicate bias to respond ‘‘word’’ and values below .5
> indicate bias to respond ‘‘nonword""

> From McKoon where they introduce response bias in exp 3: "Because the
> proportions of the two stimuli tested for the high- versus
> low-probability stimuli produced an asymmetry between re- sponses in
> accuracy of the two responses and also RTs for correct responses and
> error responses, they were not combined as they were for experiments 1
> and 2."

> You could use a hybrid (I think they do this in the last experiment
> where they have 2 conditions: left correct, right correct (i.e.
> stimulus coding)).

> In left correct you could code left to represent the upper boundary
> (i.e. 1) and in right correct you could code right to represent the
> upper boundary. This way upper boundary would always be correct but
> you are still using stimulus coding. That way positive drift would
> always mean >50% accuracy.

> I think it is helpful to think about this in terms of which boundary
> you want to mean what and that bias is relative to those boundaries.
> HDDM just estimates whatever you present it with.

> Thomas

> On Mon, Sep 10, 2012 at 8:49 AM, Guido Biele
> <g.p.bi...@psykologi.uio.no <mailto:g.p.bi...@psykologi.uio.no><g.p.bi...@psykologi.uio.no>>
> wrote:

> Hi,

> first thanks for publishing a new, improved version oh hddm!

> the hddm manual suggests that one should not accuracy-code ata
> when estimating a response bias.
> diverging from this recommendation, I just stumbled about 2 papers
> by ratcliff and colleagues, who do exactly this.*
> is the recommendation (to not accuracy code for experiments with a
> response bias) due to a reason that has to do specifically with hddm?

> Ratcliff and McKoon (2008) examine if prior probability influences
> the starting point or the drift rate. to test the effect on drift
> rate, they seem to decompose the total drift rate into 2
> components, one due to stimulus quality and one due to prior
> probability.
> Is this kind of analysis possible in the new version of hddm?
> (I am happy to do some additional coding myself if this is
> required to get this working)

> Cheers - guido

> * see
> (a) White, C. N., Ratcliff, R., Vasey, M. W., & McKoon, G.
> (2010). Using diffusion models to understand clinical disorders.
> /Journal of Mathematical Psychology/, /54/(1), 39–52.

> page 42, section 4.1
> (b) Ratcliff, R., & McKoon, G. (2008). The diffusion decision
> model: theory and data for two-choice decision tasks. /Neural
> Computation/, /20/(4), 873–922. doi:10.1162/neco.2008.12-06-420
> page 897, section 4.3

> --
> ------------------------------

>  Guido Biele
>  Email: g.p.bi...@psykologi.uio.no
>  Phone: +47 228 45172
>  Website <https://sites.google.com/a/neuro-cognition.org/guido/home>

>  Visiting Address
>  Psykologisk Institutt
>  Forskningsveien 3 A
>  0373 OSLO

>     Mailing Address
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