Fits a cumulative Gaussian to a set of probe values and subject responses
[loglik,m,d] = FitCumGauss_MES(p,r,mset,dset,lapserate,guessrate)
Computes likelihood of each combination of PSEs mset and slopes dset
given a set of probe values and responses using a cumulative Gaussian.
For ease of thinking about it you can view responses as either 0 or 1,
though in practice anything larger than 0 is treated as 1 and anything
lower than 0, including 0, is treated as 0. A 1, -1 response scheme as
input is thus no problem.
By default, a psychometric function ranging from 0% to 100% is used, as
is suitable for discrimination experiments with a standard in the middle
of the possible stimulus parameter range. For other paradigms, such as
detection tasks, one can set the guessrate input to 1/num_alternatives,
e.g. .5 when doing a 2IFC detection task.
Optinally fits with a lapse rate, which defaults to 0. If a lapse rate is
set, the cumulative Gaussian levels off at lapserate/2 and 1-lapserate/2
when the guessrate is 0. If the guessrate is non zero, the cumulative
Gaussian that is fit ranges from guessrate to 1-lapserate