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 autonomic-dependant 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 • GSRsimultaneously.
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 ( )• 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
Name
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
brown
purple
yellow
orange
bluegreen
red
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