>"John H. Casada" <casad at umich.edu> wrote:
>mdonkers at kub.nl wrote:
> > >Nate wrote:
> > >>
> > >> And secondly, what is/are the underlying mechanism(s) this is measuring?
> > >> (eg, sympathetic, parasympathetic, etc?)
> > >Sympathetic arousal. When we are anxious, fearful, our hands sweat.
> > >Sweat contains salt which increases conductance and can be measured
> > >Larry Brash
>> This seems to imply that skin conductance is actually measuring salt.
> This is problematic since the gels used in the electrodes for this
> contain isotonic saline. The salt is already present at the electrode
> site. Also, skin conductance shows both increases and decreases in a
> short time. If it was only salt being measured, this would imply that
> the skin takes up the salt again.
So it is not the salt in sweat but the moisture, dry salt is a very
poor conductor. The water evaporates, explaining the decrease.
Michael J. Duggan,
Centre for Applied Microbiology and Research,
michael.duggan at camr.org.uk
Tel 01980 612733
Fax 01981 612100