Download Lesson 11 Reaction Time

Physiology Lessons
for use with the
Biopac Science Lab MP40
Lesson 11 Reaction Time
Fixed & Pseudo-random Intervals
PC running Windows® XP or Vista
or Mac® OS X 10.4 -10.5
Lesson Revision 11.26.2007
BIOPAC Systems, Inc.
42 Aero Camino, Goleta, CA 93117
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[email protected]
www.biopac.com
© BIOPAC Systems, Inc. 2005
Biopac Science Lab
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Lesson 11 Reaction Time
I.
SCIENTIFIC PRINCIPLES
The beginning of a race is a classic example of a stimulus-response situation,
where people hear a stimulus (such as the starter’s pistol) and react to it in some
way (response). There are two key factors in stimulus-response: reaction time and
learning.
•
Reaction time is the delay between the stimulus presentation and the
beginning of the response.
•
Learning is the acquisition of knowledge or skills due to experience and/or instruction.
Fig. 11.1
The delay between hearing the signal and responding is due collectively to the time for the sensory signal to reach
the brain, the time required for the brain to process the sensory information and generate a motor response, and the
time for motor signals to reach the skeletal muscles. With learning, the time for the various steps in the process can
be shortened. Reaction time varies from person to person and from situation to situation, and most people have
delayed reaction times late at night and early in the morning.
As people learn what to expect, reaction time typically decreases. Imagine a young man entering a track event for the
first time. When the pistol goes off, he might not know what to do, but after everyone around him started running he
would get the idea and start running as well. In the next race, you would expect him to start at about the same
(although not exact) time as everyone else, assuming some learning took place in the meantime. With practice, and
more importantly, learning, his reaction times could be cut from a few seconds to fractions of a second.
Note Some years ago, a world-class runner was repeatedly accused by his competitors of “jumping the gun” in
races. He could only respond to these accusations by saying that he felt he had done nothing wrong. When
footage of his races was reviewed, it became clear that he was in fact leaving the starting blocks before his
competitors. As the evidence against him mounted, he underwent physiological testing which measured how
long it took him to respond to external events or stimuli. It was revealed that his responses were some five to
ten percent faster than those of an average runner, and this slight advantage enabled him to react faster once
he heard the starter’s pistol
This lesson shows how easily and rapidly people learn, as demonstrated by their ability to anticipate when to press a
button. The lesson uses a relatively simple variation of stimuli (pseudo-random vs. fixed interval) to determine what
results in the shortest reaction times.
ƒ
When fixed-interval trials are repeatedly performed, average reaction time typically decreases each time new
data is recorded, up to a point. Eventually, the minimal reaction time required to process information is
reached and reaction time becomes constant.
ƒ
When pseudo-random presentation trials are repeated, it takes longer for reaction times to decrease and the
decrease is less than as occurs with fixed-interval presentation.
Usually, longer reaction times are a sign that people are paying less attention to the stimuli and/or are processing
information. That is, if it took you more time to respond to clicks while also reading a book than when you were also
watching TV, then you could infer that you were probably paying more attention to the book than to TV since your
brain took longer to respond. Deriving these types of measures from simple reaction time tests allows researchers a
glimpse into the cognitive and neurological functioning of people as they perform tasks.
This lesson takes a relatively simple look at reaction time and how changing one small aspect of a procedure can
result in differences in reaction times. You will probably notice a difference in average reaction times between the
pseudo-random and fixed interval presentation trials, and this difference will most likely favor the segments with fixedinterval presentation of stimuli. Part of this difference is probably due to the random vs. non-random presentation of
the stimuli. However, you might have also noticed that reaction time decreased from pseudo-random presentation to
fixed-interval presentation, suggesting that maybe you just got better with practice.
ƒ
In more complex investigations, people might be placed in two different conditions (e.g., happy vs. sad,
watching TV vs. reading a book) and their reaction time for each condition would be measured. Variations on
this theme present people with hundreds of stimuli, often in the form of words or pictures. Although not
covered here, such investigations might measure the alpha-band EEG in addition to response time as
another indicator of attention, and review the connection between reaction times and alpha-band EEG activity
when people are paying attention to a TV program versus when they are relatively relaxed.
The process of changing the order of presentation for different groups of people is known as counterbalancing and is
commonly performed in psychological, medical and other types of research investigations that use experimental
Lesson 11: Reaction Time
Page 3
procedures. By comparing the reaction time difference between trials with differing order of presentation, you can see
how learning contributes to reaction times.
In order to compare the reaction times from the two types of presentation schedules, you can summarize the results
as statistics or measures of a population. There are certain statistics that are usually reported for the results of a
study: mean, range, variance, and standard deviation. Mean is a measure of central tendency. Range, variance and
standard deviation are measures of distribution or the “spread” of data. Using the statistics of mean and distribution,
investigators can compare the performance of groups.
ƒ
The mean is the average or the sum of the reaction times divided by the number of subjects (n).
ƒ
The range of scores is the highest score minus the lowest score. The range is affected by extremely high and
low reaction times, so investigators also describe the “spread” or distribution of times with two related
statistics: variance and standard deviation.
ƒ
Variance is determined by calculating the average squared deviation of each number from its mean.
ƒ
Standard deviation is the square root of the deviance.
In this lesson, you will calculate your group statistics, but you will not do any formal comparisons between groups.
II. EXPERIMENTAL OBJECTIVES
1. Measure and compare reaction times of an individual subject using two stimulus presentation schedules:
fixed intervals and pseudo-random intervals.
2. Introduce elements of statistics into data analysis.
3. Use statistics to determine the effects of learning on reaction times.
III. MATERIALS
ƒ
Biopac Science Lab system (MP40 and software) on computer running Windows XP or Mac OS X
ƒ
Electrode lead set (40EL Lead Set)
ƒ
Feedback Set: Feedback cable (40CBLFB1) and stereo headphones (40HP)
ƒ
Disposable vinyl electrodes (EL503), three electrodes per subject
Attention Windows Vista® users:
Windows Vista® users must reset Griffin iMic Audio Properties
The iMic USB audio adapter defaults to 1-channel audio
configuration. Lesson 11 Reaction Time requires 2-channel audio.
Prior to initial audio capture setup, the following steps are
recommended to adjust the Audio setting.
Audio Format menu > Advanced tab
1. Go to Start > Control Panel > Sound.
2. Click the 'Recording' tab and then double-click 'Microphone' to
open 'Microphone Properties'.
3. Click the 'Advanced' tab.
4. From the 'Default Format' menu, select “2 channel, 16-bit, 44100
Hz”. (48000 Hz will also work.)
5. Click 'Apply' and then click 'OK'.
6. In the 'Sound' dialog, click the 'Playback' tab.
7. Double-click 'Speakers' to open 'Speaker Properties'.
8. Click the 'Advanced' tab.
9. From the 'Default Format' menu, select “2 channel, 16-bit, 44100
Hz”. (48000 Hz will also work)
10. Restart the computer.
© BIOPAC Systems, Inc. 2005
Biopac Science Lab
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IV.
EXPERIMENTAL METHODS
A. Set Up
EQUIPMENT
SUBJECT
To Optional Adapter
Fig. 11.2 Feedback
cable via computer
red lead – bottom
white lead – top
black lead (ground) – inside wrist
Fig. 11.3 Feedback cable via adapter
FAST TRACK
1. Turn the computer ON.
Fig. 11.4 Electrode connections
Details
For direct connection to the computer, see Fig. 11.2.
For connection via USB Audio adapter, see Fig. 11.3.
ƒ A variety of USB Audio adapters can be used. Yours
Blue to Line in, Green to Line Out
may not match the sample shown but the 40CBLFB1
3. Connect the MP40 to the feedback cable (blue).
connections should always be blue to Line in and green
to Line out.
4. Connect stereo headphones (40HP) to the
feedback cable (black).
Note The extension cable (40CBLEXT) can be used between
Line Out and the 40CBLFB1.
5. Set the dial to
OFF.
2. Connect the feedback cable (40CBLFB1):
6. Attach three electrodes to the
forearm and wrist as shown above.
Attach three electrodes to the Subject’s dominant forearm and
wrist as shown in Fig. 11.4 to record activity of the extensor
digitorum, the primary muscle (located in the posterior forearm)
used to lift a finger.
ƒ The dominant side is generally the right if the subject is
right-handed or the left if the subject is left-handed.
ƒ The extensor digitorum, located in the posterior
forearm, is the primary muscle used to lift a finger.
ƒ The recording electrodes should be in the midline of the
posterior forearm about 10 cm apart; the ground can be
at the wrist.
ƒ To help define electrode placement: Place your hand on
a table, palm down, then lift (extend) the middle finger
(contract the extensor) and use your other hand to feel
the bulge as the extensor contracts.
7. Connect the electrode leads (40EL) to
the electrodes, matching lead color to
electrode position (Fig. 11.4).
Connect the leads to the Subject, matching lead color to
electrode position as shown above.
IMPORTANT
Clip each electrode lead color to its
specified electrode position
8. Start the Biopac Science Lab software.
9. Choose lesson L11-React and click
OK.
10. Type in a unique file name.
No two people can have the same file name, so use a unique
identifier, such as the subject’s nickname or student ID#.
11. Click OK.
This ends the Set Up procedure.
Lesson 11: Reaction Time
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B. Check
FAST TRACK
Details
Check System – Complete this check for the first Run a system check to confirm the feedback cable is working.
use of MP40 Feedback Cable only
1. Ignore all prompts and click Check MP40.
2. Click Devices.
3. Choose the audio input device to which the
MP40 is connected and click Check System.
4. Set the dial to
EMG (low).
5. Press and hold the
6. Click
Check pad.
when the light is flashing.
MP40 Check
7. Set the dial to
EMG (low).
8. Press and hold the
9. Click
Check pad.
when the light is flashing.
10. Wait for the MP40 Check to stop.
The MP40 Check procedure will last five seconds.
11. Subject puts on headphones and rests arm on
table.
Subject should put on headphones and then rest forearm
comfortably on a table top (or equivalent), palm down, posterior
forearm up.
12. Let go of the
Check pad.
13. Click Continue.
Signal Check
Subject lifts a finger when he/she hears the beep.
14. Click Check Signal.
15. Click OK and wait for the Signal Check to stop. At the end of the eight-second Signal Check recording, the
screen should resemble Fig.11.5.
16. Review the data.
ƒ If correct, go to the Record section.
ƒ
If incorrect, click
.
Fig. 11.5
If the recording check does not show a burst of activity for the
finger lift, click Redo Signal Check.
© BIOPAC Systems, Inc. 2005
Biopac Science Lab
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C. Record
FAST TRACK
1. Prepare for the recording.
IMPORTANT
DO NOT manually insert a marker in any
recording segment of this lesson. The
software will insert markers as needed.
Details
Watch the Help menu videos to prepare for the recording. You
will record four segments, each requiring you to react by lifting
your finger as soon as possible after hearing a click (stimulus):
a. Segments 1 and 2 present the stimuli at pseudo-random
(1-10 second) intervals.
b. Segments 3 and 4 present the stimuli at fixed intervals
(every 4 seconds).
Note It is hard to cheat on this lesson. The Biopac
Science Lab software only looks for one response
per stimulus, and it ignores responses that occur
before the first stimulus, so it doesn’t help to lift your
finger before you hear the first stimulus. If a reaction
occurs before the stimulus or more than one second
after the stimulus, it will not be used in the reaction
time summary.
2. Prepare for the recording.
Subject should be seated in a relaxed state, with headphones
on, eyes closed. Subject should rest the hand on a flat surface
so there is no muscle strain in the arm or hand.
SEGMENT 1 — Pseudo-random Trial 1
3. Click Record.
When you click Record, a pseudo-random presentation trial will
begin and an append marker labeled “pseudo-random” will
automatically be inserted.
4.
This pseudo-random presentation trial outputs a click at least
one second apart but no more than ten seconds apart.
Subject should lift-and-return the finger as
soon as possible after hearing a sound.
As soon as you hear each click through the headphone, lift-andreturn your finger.
An event marker will automatically be inserted each time a
stimulus click is output. Also, an upward pointing “pulse” will be
displayed on the screen each time the finger is lifted.
The recording will suspend automatically after 10 clicks.
5.
Review the data.
ƒ If correct, go to Step 6.
After 10 clicks, the resulting graph should resemble Fig. 11.6. A
pulse should be displayed after each event marker if the finger
lift was detected correctly.
Fig. 11.6 Clicks indicated by pulse and marker
ƒ
If incorrect, click Redo.
The data would be incorrect if:
a) The recording did not capture a response pulse for each
click.
Note If you miss more than two responses, you should
Lesson 11: Reaction Time
Page 7
consider redoing the recording.
b) The response pulse occurs before the event marker,
indicating the Subject reacted prematurely.
c) The duration of the response pulse extends into the next
marker, indicating the Subject held the finger lift too long.
SEGMENT 2 — Pseudo-random Trial 2
6.
Click Resume.
When you click Resume, the recording will continue and an
append marker labeled Pseudo-random (Trial 2) will be
automatically inserted. You will record a second pseudo-random
presentation trial.
7.
Subject should lift-and-return finger as soon
as possible after hearing a sound.
As soon as you hear each click through the headphone, lift-andreturn your finger.
An event marker will automatically be inserted each time a
stimulus click is output. Also, an upward pointing “pulse” will be
displayed on the screen each time the finger is lifted.
The recording will suspend automatically after 10 clicks.
8.
After 10 clicks, the resulting graph should resemble Fig. 11.6.
Review the data.
ƒ If correct, go to Step 9.
ƒ If incorrect, click Redo.
Data would be incorrect for the same reasons listed in Step 5.
If data is incorrect, click Redo and repeat Steps 6-8.
SEGMENT 3 — Fixed Interval Trial 1
9.
Click Resume.
When you click Resume, the recording will continue and an
append marker labeled Fixed-interval will be automatically
inserted.
This fixed-interval presentation trial outputs a click every four
seconds.
10. Subject should lift-and-return the finger as
soon as possible after hearing a sound.
As soon as you hear each click through the headphone, lift-andreturn your finger.
An event marker will automatically be inserted each time a
stimulus click is output. Also, an upward pointing “pulse” will be
displayed on the screen each time the finger is lifted.
The recording will suspend automatically after 10 clicks.
After 10 clicks have been output, the resulting graph should
resemble Fig. 11.6 (but with fixed intervals between the clicks).
11. Review the data.
ƒ If correct, go to Step 12.
ƒ If incorrect, click Redo.
Data would be incorrect for the same reasons listed in Step 5.
If data is incorrect, click Redo and repeat Steps 9-11.
SEGMENT 4 — Fixed Interval Trial 2
12. Click Resume.
When you click Resume, the recording will continue and an
append marker labeled Fixed-interval (Trial 2) will be
automatically inserted. You will record a second fixed-interval
presentation trial.
13. Subject should lift-and-return the finger at the
sound of each click.
As soon as you hear each click through the headphone, lift-andreturn your finger.
The recording will suspend automatically after 10 clicks.
14. Review the data.
ƒ If correct, go to Step 15.
After 10 clicks, the resulting graph should resemble Fig. 11.6.
© BIOPAC Systems, Inc. 2005
Biopac Science Lab
Page 8
ƒ
If incorrect, click Redo.
Data would be incorrect for the same reasons listed in Step 5. If
data is incorrect, click Redo and repeat Steps 12-14.
15. Optional: Click Resume to record additional
segments.
Optional: You can record additional segments by clicking
Resume instead of Done. A time marker will be inserted at the
start of each added segment.
16. Click Done.
A pop-up window with options will appear. Click Yes (or No if
you want to redo the last segment).
17. Click Yes.
18. Choose an option and click OK.
When you click Yes, the software will step through the data to
record the reaction times to the journal, and then a dialog with
options will be generated. Make your choice, and click OK.
ƒ If you choose Analyze current data file, go to the
Analyze section for directions.
19. Unplug the headphones.
20. Remove the electrodes.
END OF RECORDING
Unplug the headphones, disconnect the lead clips, and peel off
the electrodes.
Lesson 11: Reaction Time
Page 9
V. ANALYZE
Details
FAST TRACK
1. Enter the Review Saved Data mode and
choose the correct file.
To review saved data, choose Analyze current data file from
the Done dialog after recording data, or choose Review Saved
Data from the Lessons menu and browse to the required file.
Fig. 11.7 Reaction times for pseudo-random trial
Note Following the press of the Done button in previous
section, the program automatically calculated all 10
reaction times and average reaction times for each trial
and placed them in the journal (Fig. 11.7). Use this
journal information to fill in your data report.
2. Set up the measurement boxes as follows:
Channel
Measurement
CH 1
Delta T
The measurement boxes are above the marker region in the
data window. Each measurement has three sections: channel
number, measurement type, and result. The first two sections
are pull-down menus that are activated when you click on them.
3. Select an area from the first event marker to the A brief description of these measurements follows.
onset of the first response pulse and note the
Delta T: The Delta Time measurement is the difference in
Delta T measurement in the Data Report.
time between the end and beginning of the selected area,
which is the duration of the selected area.
A
The signal starts to get larger at the onset of each response
pulse.
Note
The “selected area” is the area selected by the I-Beam
tool (including the endpoints).
4. Set up your display window for optimal viewing
of the first event marker and pulse of the first
data segment (Fig. 11.8).
Fig. 11.8 First event marker and pulse segment
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
5. Look at the first reaction time result in the
Journal and compare this to the Delta T
measurement found above.
The two measurements should be approximately the same.
Analysis continues…
© BIOPAC Systems, Inc. 2005
Biopac Science Lab
Page 10
6. Repeat the steps above on other pulses until
you are convinced that the Journal readings are
accurate.
7. Transfer your data from the Journal to the Data This step may not be necessary if your Instructor allows you to
Report.
print out your Journal and staple it to the Data Report.
B
8. Collect data from at least five other students in
your class as needed to complete the Data
Report.
C, D, E
9. Save or print the data file.
You may save the data, save notes that are in the journal, or
print the data file.
10. Exit the program.
11. Set the dial to
Off.
END OF DATA ANALYSIS
END OF LESSON 11
Complete the Lesson 11 Data Report that follows.
Biopac Science Lab
Lesson 11
Page 11
Reaction Time
DATA REPORT
These are sample questions. You should
amend, add, or delete questions to
support your curriculum objectives.
Student’s Name:
Lab Section:
Date:
I. Data and Calculations
Subject Profile
Name
Age
Gender: Male / Female
Height
Dominant Arm: Right / Left
Weight
Reaction Time
A. Manually calculate the reaction time for the first click in Segment 1: Delta T =
_____
Subject’s Results
B. Summarize the subject’s results (copy from the software Journal)
Table 11.1
STIMULUS
NUMBER
1
REACTION TIMES (ms)
Pseudo Random
Fixed Interval
Segment 1
Segment 2
Segment 3
Segment 4
(1st trial)
(2nd trial)
(1st trial)
(2nd trial)
2
3
4
5
6
7
8
9
10
Mean
© BIOPAC Systems, Inc. 2005
Reaction Time vs Number of Presentations
C. Complete Table 11.2 with data from the first fixed-interval trial (data Segment 3) and calculate the mean for
each presentation to determine if reaction times vary as each Subject progresses through the series of
stimulus events.
Table 11.2 Comparison of Reaction Times
Student’s
Name
Pseudo-random Trial 1 Data
(Segment 1)
Stimulus
Stimulus
Stimulus
1
5
10
Fixed Interval Trial 1 Data
(Segment 3)
Stimulus
Stimulus
Stimulus
1
5
10
1.
2.
3.
4.
5.
Calculate the
Means:
Group Summary
D. Complete Table 11.3 with the mean for five students, and calculate the group mean.
Table 11.3
Class Data
Student Means
1.
2.
3.
4.
5.
Calculate the
Group Means:
Pseudo-random trials
First
Second
Fixed-interval trials
First
Second
Variance and Standard Deviation
E. Calculate the variance and standard deviation for five students with data from Segment 2: Pseudorandom Trial 2 (Table 11.4) and from Segment 4: Fixed Interval Trial 2 (Table 11.5).
Variance =
1 n
∑ (xj - x ) 2
n −1 j =1
Standard Deviation = Variance
Where
n = number of students
Xj = mean reaction time for each student
X = Group mean (constant for all students)
n
∑ = Sum of all student data
j=1
Table 11.4 Segment 2: Pseudo-random Trial 2 Data
Student
ENTER
Mean Reaction
time for Student
ENTER
CALCULATE
CALCULATE
Group Mean
Deviation
Deviation2
(X j )
(X)
(X j - X)
(X j - X)
2
1
2
3
4
5
Sum the data for all students =
=
Variance (σ2) =
Multiply by
=
Standard Deviation =
Take the square root of the variance
=
=
Table 11.5 Segment 4: Fixed Interval Trial 2 Data
Student
ENTER
Mean Reaction
time for Student
ENTER
CALCULATE
CALCULATE
Group Mean
Deviation
Deviation2
(X j )
(X)
(X j - X)
(X j - X)
1
2
3
4
5
Sum the data for all students =
=
Variance (σ2) =
Multiply by 0.25 =
=
Standard Deviation =
Square root of Variance =
=
© BIOPAC Systems, Inc. 2005
2
II. Questions
F. Describe the changes that occurred in the mean reaction time between the 1st and 10th stimuli
presentation:
For Segment 1:
For Segment 2:
Which segment showed the greatest change in mean reaction time?
G. Refer to Table 11.2 and Table 11.3:
Segment 1
Segment 2
sec
Estimate the minimal reaction time when reaction time becomes constant:
What physiological processes occur between stimuli presentation and the motor response?
H. Refer to Table 11.2:
I.
Which presentation schedule had the lowest group mean?
Refer to Table 11.2 and Table 11.3:
Pseudo-random
Fixed-interval
J.
Which of the presentation schedules seems to have less variation (lower variance and lower standard
deviation)? Pseudo-random Fixed-interval
Refer to Table 11.2 and Table 11.3:
State a plausible relationship between the difficulty of a task and the reaction time statistics: mean,
variance, and standard deviation.
K. What differences would you predict in reaction times and learning between your right and left hands?
End of Biopac Science Lab Lesson 11 Data Report
Biopac Science Lab
Page 15
VI. ACTIVE LEARNING LAB
Design a new experiment to test or verify the scientific
principle(s) you learned in the Biopac Science Lab recording
and analysis segments.
For this lesson, you might examine how reaction times
vary with the dominant and non-dominant arms, or repeat
additional trials to see if reaction times improve. You
could also introduce other elements, such as asking the
subject to read aloud or listen to music, and examine their
influence on reaction times.
Design Your Experiment
Use a separate sheet to detail your experiment design, and be
sure to address these main points:
A. Hypothesis
Describe the scientific principle to be tested or verified.
B. Materials
List the materials will you use to complete your investigation.
C. Method
Describe the experimental procedure—be sure to number
each step to make it easy to follow during recording.
ƒ
See the Set Up section or Help > About Electrodes for
electrode placement guidelines.
Run Your Experiment
D. Setup
Set up the equipment and prepare the subject for your
experiment.
E. Recording
Use the Record, Resume, and Suspend buttons in the
Biopac Science Lab program to record as many segments
as necessary for your experiment.
Click on Done when you have completed all of the segments
required for your experiment.
Analyze Your Experiment
F. Set measurements relevant to your experiment and record
the results in a Data Report.
© BIOPAC Systems, Inc. 2005