>>>> I've been doing a good deal of reading/research about stress responses
>> lately and aside from measures of HR, BP, Cortisol, etc, skin conductance
>> also often comes up.
>>>> First of all, is this the same as galvanic skin response? If not then what
>> is GSR?
>Yes, I believe it is the same
Another (more recently used) name for the same physiological process is
Electrodermal Activity (EDA).
>> 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