Download GSR-POLYGRAPH LAB

GSR-POLYGRAPH LAB
Physiology lab
GSR-Galvanic SkinResponse
• Electricity flows through an electrical circuit because of difference
in the electrical pressure between the beginning and the end of a
circuit.
• Electrical pressure (electromotive force-E) is measured in volts (V).
• The flow of electricity is called current (I=amperes)
• As electricity flows through the circuit, resistance (R) is measured in
ohms (Ω)
Ohm’s law:
I (Amps)= E(Volts)/ R (Ohms)
In this lab
• We’re going to apply principles of Ohm’s Law and record changesin the
electrical resistance of the skin.
• GSR (Galvanic skin resistance) – When a feeble electric current is steadily
applied between two electrodes placed about an inch apart, the recorded
electrical resistance between them, referred to as GSR (depends on
subject’s emotional state)
• Galvanic skin potential (GSP) – Similarly if the electrodes are connected to
a suitable voltage amplifier, but without any externally applied current,
the voltage measured between them, referred to as galvanic skin potential
(GSP)
Galvanic skin response
Galvanic skin response
• It is effected by autonomic tone (largely
sympathetic) occuring in the skin and
subcutaneous tissue in response to a change
in the state of the subject.
• Changes in peripheral autonomic tone alter
sweating and cutaneous blood flow, which in
turn change GSR and GSP.
A polygraph
• The detection and recording og the galvanic
skin responce is often combined with the
detection and recording of other autonomicdependant psycophysiological variables such
as heart rate, respiratory rate nad blood
pressure.
• The device that detects and records these
variables is called polygraph.
The experiment
• We’re gonna measure:
• Respiratory responses
• Heart rate and
• GSR
simultaneously.
Calibration
• Seat teh subject facint the director and away
from the screen.
• Click calibrate
• Three sec.after a beep will sound and subject
should inhale and exhale deeply for one cycle
then return to normal breathing.
• End calibr.
There are 3 segments
• 1. seg: Subject faces the director – recorder
faces screen and listens the directors instr. To
subject.
• Click record
• Wait 5 secs
• Recorder needs to insert an event marker at
the precise moment that the subject answers
each question (F9)
Questions
• Quietly say his-her name ( Name
)
• Quietly count backward from 10 ( count from 10)
• Count backward from 30 by substracting
increasing odd numbers-exmp. 30,29,26,21
(
count from 30)
• Director touches subject on the side of the
face
face touched
• Click suspend
Seg2
• Click resume
• Director holds paper 1
about two feet from
subject’s face
• Display the colors and
insert event markers in
the following order:
white
black
red
blue
green
yellow
orange
brown
purple
Seg3
•
•
•
•
Click resume
Director asks subject the ten questions.
Subject responds yes or no
Recorder inserts event markers when the
question asked and when the answer starts
Analysis
• Set up your display window for optimal
viewing of the first 5 secs of the recording.
• Set up the measurement boxes as follows
Respiration rate
GSR
• Scroll to view a 10 secs interval beginning at
the first event marker
BPM