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What exactly does "skin conductance" measure??

Michael Duggan michael.duggan at camr.org.uk
Mon May 19 14:44:28 EST 1997



>"John H. Casada" <casad at umich.edu> wrote:

> mdonkers at kub.nl wrote:
> > 
> > >Nate wrote:
> > >>
>      <snip>
> > >> 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,
Porton Down,
Salisbury,
Wiltshire,
SP4 0JG,
UK

michael.duggan at camr.org.uk

Tel 01980 612733
Fax 01981 612100



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