Electrodermal Activity

Question 1

What is Ohm’s Law?

Answer 1

When you hook up a resistor or conductor to a source of power, a current flows and the current is proportional to the voltage.
Unit of resistance os the Ohm.

The traditional unit of conductance was mho. Now we use microsiemens

Question 2

What are the techniques for measuring electrodermal activity?

Answer 2

• Interested in the eccrine glands as they have a wide distribution all over the body. Common on the palms of the hands and the soles of the feet. Measuring the amount of sweat in the glands, not the secretion on the skin
• Use non-polarising electrodes (Ag/AgCl), size doesn’t seem critical
• Sites: attach the electrodes to the distal phalanges of digits 2 and 3
• Make sure there is a good connection between the subject and the electrode
• Site preparation: gentle wipe with alcohol, do not rub or abrade. Often use non-dominant hand to free up dominant hand for behavioural responses

Question 3

Describe Sokolov’s Mechanism.

Answer 3

Repeated stimulation -> neuronal model of stimulus
Discrepancy between stimulus and model -> OR

Largely based on the missing stimulus effect. Sokolov noted that after a number of repetitions of a stimulus, non-representation can result in the OR

He focused on three mechanisms of OR magnitude

• Novelty: OR decreases in magnitude with stimulus repetition
• Intensity: OR magnitude is linearly related to intensity for innocuous stimuli
• Significance: attending to the stimulus leads to an increase in magnitude

Question 4

What is the difference between tonic and phasic measures?

Answer 4

Tonic - skin conductance level, what you are now, baseline, changes very slowly. SCL behaves just like Sokolov’s OR is meant to
- Pistol shooters - No significant difference in SCL between best and worst shots, Extent of HR deceleration did not predict performance

Phasic - skin conductance response, bump of small changes. What we are referring to when we generally talk about responses

Question 5

What are some of the applications electrodermal activity measures?

Answer 5

Detection of deception: lie detection control question test, guilty knowledge test

Question 6

Compare the Fere effect and the Tarchanoff effect.

Answer 6

The Fere effect uses EDA which relies on external sources of current for observation such as skin resistance response (SRR) and skin resistance level (SRL). They are exosomatic

The Tarchanoff effect is endosomatic so it doesn’t need external current. It is the difference in potential of two different areas of the skin. Skin potential reflex (SPR) and skin potential level (SPL)

Question 7

What are two circuits used to measure SCL?

Answer 7

Constant voltage: holds voltage across electrodes constant, skin varies with conductance

Constant current: potential difference between electrode varies with resistance