Lab Principles Report

Physiology Lessons

for use with the

Biopac Student Lab

PC under Windows

 98SE, Me, 2000 Pro

or Macintosh 

8.6 – 9.1

Lesson 9

GALVANIC SKIN RESPONSE

&

THE POLYGRAPH

Manual Revision

PL3.6.7-ML3.0.7/081103

Richard Pflanzer, Ph.D. Associate Professor

Indiana University School of Medicine

Purdue University School of Science

William McMullen Vice President

BIOPAC Systems, Inc.

BIOPAC Systems, Inc. 42 Aero Camino, Goleta, CA 93117

(805) 685-0066, Fax (805) 685-0067

Email: [email protected]

Web Site: http://www.biopac.com

Page 2 Lesson 9: GSR & Polygraph BIOPAC Student Lab

I. INTRODUCTION

Electricity flows through an electrical circuit because of a difference in electrical pressure

between the beginning and the end of a circuit. Electrical pressure or electromotive force (E)

is measured in volts (V). The flow of electricity, called current (I), is measured in amperes

(A) or amps for short. As electricity flows through the circuit, resistance to flow occurs.

Electrical resistance (R) is measured in ohms ().

In a simple circuit of direct electrical current, the relationship between the electromotive

force causing the electrical current, the resistance to flow of electricity, and the resultant

magnitude of the current is described by Ohm‘s Law.

Ohm’s Law: I (Amps) = E (Volts) / R (Ohms)

If two of the three variables are known, the unknown third variable can be calculated.

For example, if voltage and resistance values for a simple circuit are known,

the above formula can be used to calculate the value for current; if the values

for current and resistance are known, then the formula for computing voltage

is E = IR.

Ohm‘s Law implies that if a constant current is applied across a resistance, changes in the

resistance will produce a voltage change directly proportional to the resistance change.

For example, if a constant current of 1.0 ampere is applied across a resistance

of 2.0 ohms, the measured voltage would be 2.0 volts (I = E/R, 1.0 ampere =

2.0 volts/2.0 ohms). If the resistance dropped to 0.5 ohm, the voltage would

also fall to 0.5 volt (I = E/R, 1.0 amperes = 0.5 volt/0.5 ohm).

In this lesson, you will apply principles of Ohm‘s Law and record changes in the electrical

resistance of the skin.

The human skin displays several forms of bioelectric phenomena, especially in areas of the

extremities such as the fingers, palms of the hands, and soles of the feet.

 Galvanic skin resistance (GSR) — 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 the galvanic skin resistance (GSR), varies in accordance

with the emotional state of the subject.

 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 the galvanic skin potential (GSP), varies with

the emotional state of the subject.

The combined changes in the GSR and GSP related to the emotion of the subject constitute

the galvanic skin response.

Biopac Student Lab Lesson 9: GSR & Polygraph Page 3

The physiological basis of the galvanic skin response is a change in autonomic tone, largely

sympathetic, occurring in the skin and subcutaneous tissue in response to a change in the

affective state of the subject. Changes in peripheral autonomic tone alter sweating and

cutaneous blood flow, which in turn change GSR and GSP.

For example, if a painful stimulus such as a pinprick is applied to the skin in

an area distant to the electrode, the stimulus will reflexively elicit a general

phasic sympathetic discharge to sweat glands, increasing secretion. The

increase in sweat, although generally small, lowers the electrical resistance of

the skin because sweat contains water and electrolytes, both of which

increase electrical conductivity of the skin.

As in the case of somatic sensory stimuli (e.g., pain, pressure, touch), changes in emotion

elicit changes in peripheral autonomic tone and hence the galvanic skin response. A common

example is the vasodilation of cutaneous blood vessels of the face (blushing) and increased

sweating that often occur in the emotional state of embarrassment.

The detection and recording of the galvanic skin response is often combined with the

detection and recording of other autonomic-dependent psychophysiological variables such as

heart rate, respiratory rate, and blood pressure. The device that detects and records these

variables is called a polygraph. Although many people think polygraph is synonymous with

lie detector, the literal meaning is ―many measures‖ (poly - many, graph – write). This lesson

is a polygraph in the true sense of the word since it uses three types of measures: (a) GSR, (b)

respiration, and (c) heart rate.

One of the underlying principles involved in using the polygraph as a lie detector is that

autonomic nervous system control of heart rate, respiratory rate, blood pressure and flow, and

sweating cannot consciously be altered. Another principle is that changes in emotion

associated with intentional falsification of answers to carefully selected and worded questions

involuntarily and subconsciously alters autonomic output in such a way as to cause

recognizable changes in recorded physiological variables.

In the experiments that follow, you will record respiration, GSR, and heart rate under various

experimental procedures so as to gain a better understanding of polygraphy, its applications,

and its limitations.

It is important to keep in mind that although the recording procedures and measures

used are similar to those that might be used in a real polygraph recording, this is not a ―lie

detector test.‖ All you will do here is record the Subject‘s physiological responses to

certain questions. Some types of physiological responses are typically associated with

―lying,‖ although even under the best conditions about one-third of innocent people ―fail‖

lie detector tests. The best you can hope for here is to get a better understanding of how

these types of procedures work.

Page 4 Lesson 9: GSR & Polygraph BIOPAC Student Lab

II. EXPERIMENTAL OBJECTIVES

1) To become familiar with procedures for recording the galvanic skin response.

2) To observe and record changes in respiratory rate, heart rate, and skin resistance

associated with somatic and special sensory stimuli.

3) To observe and record changes in respiratory rate, heart rate, and skin resistance

associated with cognitive behavior and emotion.

4) To analyze a 3-channel polygram recorded under various experimental conditions to gain

a better understanding of polygraphy and its potential for use and misuse.

III. MATERIALS

 BIOPAC disposable vinyl electrodes (EL503) – 3 electrodes per Subject

 BIOPAC Electrode lead set (SS2L)

 BIOPAC Electrode gel (GEL1)

 BIOPAC GSR transducer (SS3L)

 BIOPAC Respiration transducer (SS5LB or older SS5LA or SS5L)

 BIOPAC PAPER1 or nine sheets of different colored paper. Recommended: 8-1/2‖x 11‖

sheets of: white, black, green, red, blue, yellow, orange, brown, purple.

 Computer system

 Biopac Student Lab software v3.6.7 PC or v3.0.7 Mac or greater

 BIOPAC acquisition unit (MP30)

 BIOPAC wall transformer (AC100A)

 BIOPAC serial cable (CBLSERA) or USB cable (USB1W) if using a USB port.

Biopac Student Lab Lesson 9: GSR & Polygraph Page 5

IV. EXPERIMENTAL METHODS

Overview

 As you complete the Experimental Methods (Set Up, Calibration, and Recording) and the Analysis,

you may need to use the following tools and/or display options. The window display shown below is

only a reference sample — it does not represent any lesson specific data. The sample screen shows 3

channels of data and four channel measurement boxes, but your screen display may vary between

lessons and at different points within the same lesson.

channel measurement boxes (channel # measurement type result)

)

marker label

channel boxes (Data analysis mode only)

marker marker tools

selection tool

I-Beam cursor

zoom tool horizontal (time) scroll bar

horizontal scale

vertical scales

vertical (amplitude) scroll bar

channel labels

 The symbols explained below are used throughout Experimental Methods and Analysis.

Key to Symbols

 If you encounter a problem or need further explanation of a concept, refer to the

Orientation Chapter for more details.

 The data collected in the step needs to be recorded in the Data Report (in the section

indicated by the alpha character). You can record the data individually by hand or choose

Edit > Journal > Paste measurements to paste the data to your journal for future

reference.

 Most markers and labels are automatic. Markers appear at the top of the window as inverted triangles. This symbol is used to indicate that you need to insert a marker and key

in a marker label similar to the text in quotes. You can insert and label the marker during

or after acquisition. On a Mac, press ―ESC‖ and on a PC, press ―F9.‖

 Each section is presented in a two-column format, as described below.

FAST TRACK STEPS

This side of the lesson (left, shaded

column) is the ―FAST TRACK‖ through

the lesson, which contains a basic

explanation of each step.

DETAILED EXPLANATION OF STEPS

This side of the lesson contains more detailed

information to clarify the steps and/or concepts in the

FAST TRACK, and may include reference diagrams,

illustrations, and screen shots.

Page 6 Lesson 9: GSR & Polygraph BIOPAC Student Lab

A. SET UP

FAST TRACK Set Up Detailed Explanation of Set Up Steps

1. Turn the computer ON. The desktop should appear on the monitor. If it does not

appear, ask the laboratory instructor for assistance. 

2. Make sure the BIOPAC MP30 unit

is turned OFF. 

3. Plug the transducers in as follows:

Respiration (SS5LB) — CH 1

Electrode lead set (SS2L) — CH 2

GSR (SS3L/SS3LA) — CH 3

BIOPAC MP30 unit

Respiratory Transducer

(SS5LB or SS5LA

or SS5L) plugs into

CHannel 1

Electrode lead set(SS2L)

plugs into CHannel 2

GSR (SS3L or SS3LA)

plugs into CHannel 3

Fig. 9.1 Equipment Connections

4. Turn the MP30 Data Acquisition

Unit ON.



5. Attach the respiratory transducer

(SS5LB) to the Subject (Fig. 9.2).

IMPORTANT USE NOTE

If using the SS5LA transducer,

you must be very careful to not

pull or yank on the rubber bow

tie portion that contains the

sensor element.

Set up continues…

Attach the respiratory transducer around the chest below

the armpits and above the nipples (Fig. 9.2). The correct

tension is critical. The respiratory transducer must be

slightly tight at the point of maximal expiration. The

respiration transducer can be applied over thin clothing,

such as a t-shirt.

Fig. 9.2 SS5LB Placement

Biopac Student Lab Lesson 9: GSR & Polygraph Page 7

If using the SS5LB or SS5L, simply attach the Velcro

ends together at the correct tension.

If using the SS5LA, attach the nylon belt by threading

the nylon strap through the corresponding slots on the

rubber bow tie such that the strap clamps into place when

tightened (Fig. 9.3)

Fig. 9.3

6. Fill both cavities of the GSR

transducer (SS3L/SS3LA) with gel

and attach to the Subject (Fig. 9.4).

IMPORTANT

You must fill both sensor cavities

with electrode gel (GEL1) before

placing on the fingers.

Set up continues…

You must fill the each cavity of the SS3L/SS3LA GSR

transducer with electrode gel to obtain accurate

recordings.

The SS3L and SS3LA attach to the fingertips in an

identical manner (Fig. 9.4) and should be in place for at

least five minutes prior to the start of recording.

Sensors attach to bottom of fingertips

Velcro straps wrap around

fingers

Fig. 9.4 SS3L/SS3LA attachment and connection

The SS3L/SS3LA is typically placed on the index and

middle finger of the left hand.

Page 8 Lesson 9: GSR & Polygraph BIOPAC Student Lab

Position the transducer so that the sensor is on the bottom

of your fingertip (the part without the fingernail) and

wrap the Velcro 

tape around the finger so the transducer

fits snugly but not so tight that blood circulation is cut

off. It‘s a fine line between tight and too tight.

HINT For a good signal to be picked up, it helps if the subjects have a little sweat on their hands (not a lot, but enough so that their hands are not completely smooth or cold). If subjects wash their hands just prior to the recording or

if they have been sitting in a cold room, then they must do something to activate the sweat glands before beginning calibration or recording. If subjects begin with colder hands, the scale will be diminished and the signal will be easily saturated once they “warm up” during the lesson.

7. Place three electrodes on the Subject

(Fig. 9.5).

Set up continues…

Place three electrodes at the positions shown (Fig. 9.5).

one on right forearm (just above wrist)

one on inside right leg (just above ankle bone)

one on inside left leg (just above ankle bone)

Fig. 9.5

 Place one electrode on the medial surface of the

right leg, just above the ankle bone

 Place one electrode on the medial surface of the

left leg, just above the ankle bone

 Place one electrode on the right anterior forearm

just above the wrist (same side of arm as the palm

of hand).

Note: For optimal electrode adhesion, the electrodes should

be placed on the skin at least 5 minutes before the start of

the Calibration procedure. 

Biopac Student Lab Lesson 9: GSR & Polygraph Page 9

8. Attach the electrode lead set (SS2L)

to the electrodes (Fig. 9.6)

right forearm WHITE lead

right leg BLACK lead

(ground)

left leg RED lead

Fig. 9.6

Each of the pinch connectors on the end of the electrode

cable needs to be attached to a specific electrode. The

electrode cables are each a different color. Follow Fig.

9.6 to ensure that you connect each cable to the proper

electrode.

The pinch connectors work like a small clothespin, but

will only latch onto the nipple of the electrode from one

side of the connector.

When the electrode cable is connected properly, the

LEAD II electrode configuration will be established.

9. Start the BIOPAC Student Lab

Program. 

10. Choose Lesson 9 (L09-Poly-1). 

11. Type in your filename. Use a unique identifier. 

12. Click OK.

END OF SET UP

This ends the Set Up procedure.

Page 10 Lesson 9: GSR & Polygraph BIOPAC Student Lab

B. CALIBRATION

The Calibration procedure establishes the hardware‘s internal parameters (such as gain, offset, and

scaling) and is critical for optimum performance. Pay close attention to the Calibration procedure.

FAST TRACK Calibration Detailed Explanation of Calibration Steps

1. Seat the Subject facing the

Director and away from screen.

Fig. 9.7

Ideally, the Subject should sit in a chair facing the

Director, with arms on the armrest and be in a relaxed

state, breathing normally.

The Subject should not be able to see the screen during

recording.

2. Click on Calibrate. The Calibrate button is in the upper left corner of the

Setup window.

3. Three seconds into the recording, a

beep will sound and Subject should

inhale and exhale deeply for one

cycle, then return to normal

breathing.

The program needs to see a change in the GSR recording

during calibration.

4. Wait for the Calibration to stop.

Calibration continues…

The Calibration will run for 10 seconds and then stop

automatically, so let it run its course.

Biopac Student Lab Lesson 9: GSR & Polygraph Page 11

5. Check your calibration data. At the end of the 10-sec calibration recording, your screen

should resemble Fig. 9.8.

Figure 9.8

 If similar, proceed to the Data

Recording section.

All three recording channels should show some

fluctuation. There should be some variation 4-6 seconds

into the GSR recording from the deep inhale.

 If different, Redo Calibration.

END OF CALIBRATION

If a channel does not show fluctuation, then it is possible

that a transducer is not connected properly or the Subject

did not inhale deeply enough, and you must redo

calibration by clicking on the Redo Calibration button

and repeating the entire calibration sequence.

Page 12 Lesson 9: GSR & Polygraph BIOPAC Student Lab

C. RECORDING LESSON DATA

FAST TRACK Recording Detailed Explanation of Recording Steps

1. Prepare for the recording. You will record three segments of data, 120 seconds each.

In order to work efficiently, read this entire section so you

will know what to do for each recording segment.

Check the last line of the journal and note the total amount

of time available for the recording. Stop each recording

segment as soon as possible so you don‘t use an excessive

amount of time (time is memory).  Hints for obtaining optimal data:

a) The Subject must not be able to see the record as it is

being recorded.

b) The environment must be quiet.

c) Sensory input to the Subject must be kept at a

minimum since almost any change in the environment

may evoke a response.

d) Subject needs to be relaxed with arms resting on the

armrest.

e) The Subject should remain as still as possible during

recording.

f) Subject should answer question in a quiet tone with

minimal movement of the mouth.

g) Subject should be at his/her resting heart rate in a

relaxed mental and physical state, and should not have

performed any recent physical or mental exertion.

Segment 1

2. Take position as follows:

a) Subject faces Director.

b) Recorder faces screen and

listens for Director‘s

instructions to Subject.

Subject should be in a chair in a relaxed state, with arms on

the armrest, breathing normally.

Recorder will need to listen for Director‘s instructions to

Subject so s/he knows when to place markers.

3. Click on Record. The recording will begin.

4. Wait five seconds, then Director

instructs Subject to perform the

following, and pauses between

requests to reestablish a baseline.

Recording continues…

The 5-second wait establishes a baseline.

This segment should be completed within 120 seconds.

To insert Markers: Mac = Esc key, PC = F9 key.  Markers can be entered or edited after the data is recorded.

Biopac Student Lab Lesson 9: GSR & Polygraph Page 13

Recorder inserts markers to indicate

event change.

a) Quietly say his/her name.

 ―name‖ b) Quietly count backward from 10.

 ―count from 10‖ c) Count backward from 30 by

subtracting increasing odd

numbers (e.g., 30, 29, 26, 21).

 ―count from 30‖ d) Director touches Subject on the

side of the face.

 ―face touched‖

It may be too difficult to type in the marker label text while

you are recording. The important thing is to get the marker

inserted during recording, at the precise moment the event

changes. Labels can be keyed after the recording is done.

Subtract 1 from 30, then 3 from 29, then 5 from 26 and so

on, by using increasing odd numbers as the subtracted

factor.

5. Click on Suspend. The recording should halt, giving you time to review the

data and prepare for the next recording segment.

6. Review the data on the screen.

 If correct, go to Step 7.

If all went well, your data should look similar to Fig. 9.9

and you can proceed to Step 7.

Fig. 9.9

 If incorrect, click on Redo. The data would be incorrect if:

a) the Suspend button was pressed prematurely.

b) A transducer slipped off or an electrode peeled up,

causing a large baseline drift, spike, or loss of

signal.

c) The markers were not inserted or were inserted at

the wrong time(s).

In this case, you should redo the recording by clicking on

―Redo‖ and repeating Steps 2-6. Note that once you press

Redo, the data you have just recorded will be erased.

Recording continues…

Page 14 Lesson 9: GSR & Polygraph BIOPAC Student Lab

Segment 2

7. Click on Resume. This segment should be completed within 120 seconds.

The recording will continue from the point where it last

stopped, and a marker labeled ―Concentration on colored

squares‖ will automatically come up when Resume is

pressed.

8. Director holds PAPER1 colored

squares about two feet from

Subject’s face.

Director instructs Subject to look at

and concentrate on each square for

about 10 seconds, and pauses

between requests to reestablish a

baseline.

Recorder inserts markers to indicate

color change and records the time

required for a stimulus to generate a

response.

Display the colors and insert

markers in the following order:

a)  ―white‖

b)  ―black‖

c)  ―red‖

d)  ―blue‖

e)  ―green‖

f)  ―yellow‖

g)  ―orange‖

h)  ―brown‖

i)  ―purple‖

To insert Markers: Mac = Esc key, PC = F9 key. Markers

can also be entered or edited after the data is recorded.

9. Click on Suspend. The recording should halt, giving you time to review the

data and prepare for the next recording segment.

Recording continues…

Biopac Student Lab Lesson 9: GSR & Polygraph Page 15

10. Review the data on the screen.

 If correct, and more segments are

required, go to Step 11.

If all went well, your data should look similar to Fig. 9.10

and you can proceed to Step 11.

Note: In the sample recording, only four colored sheets

were used.

Fig. 9.10

Variation in the data will completely depend on the Subject

and recording conditions.

 If incorrect, click on Redo. The data would be incorrect for the reasons in Step 6.

If incorrect, you should redo the recording by clicking on

―Redo‖ and repeating Steps 7-10. Note that once you press

Redo, the data you have just recorded will be erased.

Segment 3

11. Click on Resume. This segment should be completed within 120 seconds.

The recording will continue from the point where it last

stopped, and a marker labeled ―series of ‗Yes/No‘

questions‖ will automatically come up when Resume is

pressed.

12. Director asks Subject the ten

questions below, and notes Subject‘s

response.

Subject responds ―yes‖ or ―no.‖

Recorder inserts a marker when the

question is asked and another marker

when Subject begins to answer.

 ―Q‖ when question asked

 ―A‖ when answer starts

Recording continues…

Each question-answer should take about 10 seconds.

Subject‘s replies should be limited to ―yes‖ or ―no.‖

Subject may answer truthfully or dishonestly.

To insert Markers: Mac = Esc key, PC = F9 key.

Markers can be edited after the data is recorded.

a) Are you currently a student? Y N Director should note Subject‘s responses here by circling Y

Page 16 Lesson 9: GSR & Polygraph BIOPAC Student Lab

b) Are your eyes blue? Y N

c) Do you have any brothers? Y N

d) Did you earn an ―A‖ on the last

physiology exam? Y N

e) Do you drive a motorcycle? Y N

f) Are you less than 25 years of

age? Y N

g) Have you ever traveled to

another planet? Y N

h) Have aliens from another planet

visited you? Y N

i) Do you watch ―Seinfeld‖? Y N

j) Have you answered all of the

preceding questions truthfully?

Y N

for yes and N for No

13. Click on Suspend. The recording should halt, allowing you to review the data.

14. Review the data on the screen.

 If correct, go to Step 15.

If all went well, your data should look similar to Fig. 9.11

and you can proceed to Step 15.

Fig. 9.11

Variation in the data will completely depend on the Subject

and recording conditions.

 If incorrect, click on Redo. The data would be incorrect for the reasons in Step 6.

If incorrect, you should redo the recording by clicking on

―Redo‖ and repeating Steps 11-14. Note that once you

press Redo, the data you have just recorded will be erased.

Recording continues…

15. Ask the Subject to answer the

questions honestly and note the

Flip to Table 9.3 in your Data Report and record the

Biopac Student Lab Lesson 9: GSR & Polygraph Page 17

truthful answer in the Data Report.

 C

Subject‘s truthful answers to each question.

16. Click on Done. A pop-up window with four options will appear. Make your

choice, and continue as directed.

If choosing the ―Record from another Subject‖ option:

a) Attach the sensors per Set Up Steps 5, 6, and 7 and

continue the entire lesson from Set Up Step 10.

b) Each person will need to use a unique file name.

17. Remove the sensors.

END OF RECORDING

Page 18 Lesson 9: GSR & Polygraph BIOPAC Student Lab

V. DATA ANALYSIS

FAST TRACK Data Analysis Detailed Explanation of Data Analysis Steps

1. Enter the Review Saved Data mode

and choose the correct file.

Enter Review Saved Data from the Lessons menu. 

Note Channel Number (CH)

designations:

Channel Displays

CH 3 GSR

CH 40 Respiration

CH 41 Heart Rate

Fig 9.12

2. Setup your display window for

optimal viewing of the first 5

seconds of the recording.

The following tools help you adjust the data window: 

Autoscale horizontal Horizontal (Time) Scroll Bar

Autoscale waveforms Vertical (Amplitude) Scroll Bar

Zoom Tool Zoom Previous

3. Set up the measurement boxes as

follows:

Channel Measurement

CH 41 value

CH 40 BPM

CH 3 value

CH 3 none

Data Analysis continues…

The measurement boxes are above the marker region in the

data window. Each measurement has three sections:

channel number, measurement type, and value. The first

two sections are pull-down menus that are activated when

you click on them. The following is a brief description of

these specific measurements. 

value: displays the amplitude value for the channel at the

selected point. If a single point is selected, the value is for

that point, if an area is selected, the value is the endpoint

of the selected area.

BPM: In this lesson, the BPM measurement stands for

Breaths Per Minute and calculates the difference in time

between the end and beginning of the selected area (same

as T), then divides this value into 60 seconds/minute.

none: turns off the measurement channel.

The ―selected area‖ is the area selected by the I-Beam tool

(including the endpoints).

Biopac Student Lab Lesson 9: GSR & Polygraph Page 19

4. Using the I-Beam cursor, choose a

point at the 2-second mark and

record the heart rate and GSR values

(Fig. 9.13).

 A

Fig 9.13

5. Using the I-Beam cursor, select an

area from the start of one inhale to

the start of the next inhale (Fig.

9.14), and record the respiration rate

(BPM).

 A

The respiration transducer records chest expansion

(inhalation) as positive values, and chest deflation

(exhalation) as negative values. Therefore, the start of

inhalation is recorded as the beginning of the ascending

positive waveform.

Note: This measurement may be difficult to perform,

depending on your data, because small dips in chest

expansion can occur within the normal cycle. You must

be able to distinguish the small dips from the big dips.

Fig 9.14

6. Scroll to view a 10-second interval

beginning at the first marker.

This 10-second interval should show the Subject‘s response

to the first instruction.

7. Find the point of maximal GSR

within this 10-second segment and

record the heart rate and GSR values

at this point.

 A

Data Analysis continues…

Fig 9.15

Page 20 Lesson 9: GSR & Polygraph BIOPAC Student Lab

8. Using the I-Beam cursor, select an

area from the start of one inhale to

the start of the next inhale, closest to

the point used in Step 7 and record

the respiration rate (BPM).

 A

The respiration transducer records chest expansion

(inhalation) as positive values, and chest deflation

(exhalation) as negative values. Therefore, the start of

inhalation is recorded as the beginning of the ascending

positive waveform.

Fig 9.16

9. Repeat Steps 5-7 for each condition

in Segment 1 of your data.

 A

Each condition in the data record should be separated by a

marker (―‖).

10. Repeat Steps 7-8 for Segment 2

data.

 B

11. Repeat Steps 7-8 for Segment 3

data, using a 5-second interval

beginning at the ―A‖ marker.

 C

Measurements should be taken in the interval that begins

when the Subject started to answer.

12. Save or print the data file. You may save the data to a floppy drive, save notes that are

in the journal, or print the data file. 

13. Exit the program. 

END OF DATA ANALYSIS

END OF LESSON 9 Complete the Lesson 9 Data Report that follows.

Biopac Student Lab Lesson 9: GSR & Polygraph Page 21

Lesson 9

GALVANIC SKIN RESPONSE & THE POLYGRAPH

DATA REPORT

Student’s Name:

Lab Section:

Date:

Subject Profile

Name Height

Age Weight

Gender: Male / Female

I. Data and Calculations

A. Complete Table 9.1 with Segment 1 data.

Mark I for increase, D for decrease, and NC for no change relative to baseline.

Table 9.1 Segment 1 Data

Procedure Heart Rate Respiratory Rate GSR

[CH 41 Value] [CH 40 BPM] [CH 3 Value]

Resting (baseline)

Quietly say name

Count from 10

Count from 30

Face touched

Page 22 Lesson 9: GSR & Polygraph BIOPAC Student Lab

B. Complete Table 9.2 with Segment 2 data.

Mark I for increase, D for decrease, and NC for no change relative to baseline.

Table 9.2 Segment 2 Data

Square Color Heart Rate Respiratory Rate GSR

[CH 41 Value] [CH 40 BPM] [CH 3 Value]

white

black

red

blue

green

yellow

orange

brown

purple

C. Complete Table 9.3 with Segment 3 data.

Mark I for increase, D for decrease, and NC for no change relative to baseline.

Table 9.3 Segment 3 Data

Question Answer Truth Heart Rate Respiratory Rate GSR

[CH 41 Value] [CH 40 BPM] [CH 3 Value]

Student? Y N Y N

Blue eyes? Y N Y N

Brothers? Y N Y N

Earn “A”? Y N Y N

Motorcycle? Y N Y N

Less than 25? Y N Y N

Another planet? Y N Y N

Aliens visit? Y N Y N

“Seinfeld”? Y N Y N

Truthful? Y N Y N

Biopac Student Lab Lesson 9: GSR & Polygraph Page 23

II. Questions

D. Of what practical value is the GSR information obtained from the color experiment?

E. What major physiological changes account for the galvanic skin response?

F. Give three reasons why polygraph testing of a person‘s sincerity and honesty may yield inconclusive results.

End of Lesson 9 Data Report