Response Time: An Introduction to the Nervous System
Model 1: Exploration of Stimulus-Response Time
Procedure:
1 Collect a meter stick and find a desk.
2. Support your arm on the edge of a desk so that you cannot move it down.
3. Make sure your hand extends over the edge of the desk.
4. Hold your thumb and index finger approximately 2.5 cm apart.
5. Have your partner hold the meter stick so that the 0 end of the meter stick is
even with top of your index finger and thumb.
6. Have your partner drop the stick (Partner does not countdown or say
anything).
7. Without moving your arm, catch the meter stick and hold it so that you can
measure the distance it travelled before you caught it.
8. Measure and record the distance from the o end to the top of your index
finger. Record this distance in Table #1.
9. To approximate the reaction time in seconds, divide the distance in cm by
22.1 and record the calculated reaction time in Table #1.
10. Repeat this procedure two more times, then determine your average for both
distance and reaction time.
11. Repeat the process with each of your group members, and record their data
in their Table #1.
12. Complete Table #2 by sharing the average distance and reaction time data
with your group members.
Control Reaction Times
Table #1, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
Table #1, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
1
1
2
2
3
3
Average
Average
Table #1, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
Table #1 Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
1
1
2
2
3
3
Average
Average
Student Name
Table #2
Average distance
(cm)
Average reaction
time (sec)
Use the data in Table #2 to answer the following questions:
Answers to all questions should not be taken literally. Teachers may delve deeper into
answers per course requisites. For example, teachers may wish to cover auditory,
visual or other CNS centers and pathways, spinal cord pathways, introduction of
left/right cross over points along with damage (stroke, physical trauma, etc.). Further
extension could include autonomic, action potentials, neuromuscular junction, etc.
1. Within your group, who had the fastest average reaction time? Slowest reaction
time?
Answers based on student data
2. Calculate the difference between the fastest and slowest reaction times in your
group.
Answers based on student data
3. Why do you think there was a difference between the individual with the fastest
average reaction time and the individual with the slowest average reaction time in
your group?
Subject anticipation, athletic ability, distraction, lack of sleep, etc. A good website
for further research on reaction times is:
http://biology.clemson.edu/bpc/bp/Lab/110/reaction.htm
4. A hundred dollar bill measures 15.6 cm long. Would anyone in your group be
able to grab a dollar bill before it slips through their fingers? Cite evidence from
your data above in your answer?
Answer based on student data. Most likely no because more than 15.6 cm pass
through the student’s fingers
5. List 3-5 basic processes of the nervous system that occur in your body when you
catch the meter stick (step 7 of the procedure).
This question is divergent and gets students to reflect before moving to Model 2.
Answer should focus on the pathway from visual stimulus to central processing to
skeletal muscle response. Answers may vary in detail and anatomic terms used
depending on student’s background knowledge. A very simple answer could be
1.see; 2. decide to catch, and 3. grab. An intermediate response could be: 1.
stimulus; 2. carrying the message to the brain; 3. deciding to grab; 4. carrying the
message to the muscle; and 5. grabbing the meter stick. A more detailed answer
could include: 1. Visual receptors in the eyes; 2. Conduction to the brain along
the Somatic Sensory Pathway of the Sensory Division of the PNS; 3. CNS
integration and control; 4. Conduction along the Somatic Motor Pathway of the
Motor Division of the PNS; 5. Skeletal muscle response.
Model #2: Basic organization of the nervous system:
1. Draw arrows on Figure 1 of Model 2 that indicate the direction of the flow of
information you observed in the reaction time activity of Model 1.
2. Which major division of the nervous system carries sensory information from the
somatic sensory division to the information processing center?
PNS
3. Which major division of the nervous system carries motor information to the
muscles?
PNS
4. What organ(s) make up the information processing center?
spinal cord and brain
5. Color the central nervous system red on Figure 2. Color the peripheral nervous
system blue on Figure 2.
Brain and spinal cord; Note the visceral sensory and autonomic nerves leading to
the lungs
Model #3—Distracted Reaction Time
Procedure:
1 Support your arm on the edge of a desk so that you cannot move it down.
2. Make sure your hand extends over the edge of the desk.
3. Hold your thumb and index finger approximately 2.5 cm apart.
4. Have your partner hold the meter stick so that the 0 end of the meter stick is
even with top of your index finger and thumb.
5. When ready, sing “Happy Birthday” or quickly recite the “ABC’s” out loud.
6. Have your partner drop the stick. Keep singing “Happy Birthday” or reciting
“ABC’s” over and over! Do not have your partner countdown or say anything.
7. Without moving your arm, catch the stick and hold so that you can measure
the distance.
8. Measure and record the distance to the top of your index finger in Table #3.
9. To approximate the reaction time in seconds, divide the distance in cm by
22.1 and record calculated distracted reaction times in Table #3.
10. Repeat this procedure two more times, then determine an average for both
distance and distracted reaction time.
11. Repeat the process with each of your partners, and record their distracted
reaction time data in their Table #3. Complete Table #4 by sharing data with
your partners in your group.
Distracted Reaction Times
Table #3, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
Table #3, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
1
1
2
2
3
3
Average
Average
Table #3, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
Table #3, Student Name:
Trial #
Distance
Reaction time
(cm)
(sec)
1
1
2
2
3
3
Average
Average
Student
Name
Average time
CONTROL
(sec)*
Table #4
Average time
DISTRACTED
(sec)
Difference in reaction time
(CONTROL – DISTRACTED)
*Copy the average times from your Control Reaction Time (Table #2 of Model 1)
Use the data in Table #4 to answer the following questions:
1. Who had the fastest average distracted reaction time? Slowest distracted
reaction time?
Answers based on student data
2. Calculate the difference between the fastest and slowest distracted reaction
times in your group.
Answers based on student data
3. Explain why differences exist between individuals in your group.
subject anticipation, athletic ability, distraction, lack of sleep, etc.
4. Speculate as to why there was a difference between the average reaction time in
this activity as compared to the first activity where there was not a distraction.
interruption of the pathway from stimulus to response
5. Are there instances in your group where reactions actually decreased during this
activity? Explain why this may happen.
yes/no—ability to multi-task, practice from first attempt, or multi-tasking while
playing video games, etc.
Application
1. Which variables might a driver experience that could alter reaction time when
required to brake suddenly? List as many as possible.
Eating, texting, reading the newspaper, talking on the phone, distractions from
passengers, playing with the radio, intoxicants, outside distractions, lack of sleep,
etc.
2. Pick one example from your list and describe the point at which the reaction was
interrupted.
Answers will vary with the situation—intoxicants slow down the central nervous
system, etc.
The following data chart shows the results of two separate drivers under various driving
conditions. The two drivers performed the tests at 35 mph (miles per hour) and at 70
mph. Use the following data to answer the questions below.
35 mph
70 mph
Driver I
Driver II
Driver I
Driver II
Baseline:
.45 sec.
.57 sec
.39 sec.
.56 sec.
Alcohol impaired:
.46 sec.
.64 sec
.50 sec.
.60 sec.
Reading text message:
.57 sec.
1.36 sec
.50 sec.
.91 sec.
Texting:
.52 sec.
1.44 sec
.48 sec.
1.24 sec.
(Source: Car and Driver. June 25, 2009)
Note: “Baseline” represents reaction times under normal driving conditions.
3. Summarize the reaction times of Driver I at both speeds, comparing baseline
reactions to alcohol impaired, reading a text, and texting reaction times:
Driver I’s distractions all increased his reaction times; at 35 mph alcohol least,
sending a text second, and reading a text most. At 70 mph, sending a text
increased his reaction time the least, and alcohol tied with reading a text.
4. Summarize the reaction times of Driver II at both speeds, comparing baseline
reactions to alcohol impaired, reading a text, and texting reaction times:
Driver II’s distractions all increased his reaction times; at 35 mph, alcohol
increased his reaction time the least, but sending a text and reading a text more
than doubled his reaction rate. Texting increased his reaction time the most. At
70 mph, his reaction times were faster than at 35 mph. The order remained the
same (alcohol increased reaction time the least, followed by sending a text, and
texting increased his reaction time the most.)
5. Explain possible reasons for differences in reaction times between Driver I and
Driver II.
Driving experience, biologic variability, and (as seen in the video) Driver I is
younger than Driver II.
“But the [reaction times] don't tell the whole story. Looking at Driver I’s slowest reaction
time at 35 mph, he traveled an extra 21 feet (more than a car length) before hitting the
brakes while reading a text and went 16 feet longer while texting. While reading a text
and driving at 35 mph, Driver II’s average baseline reaction time of 0.57 second nearly
tripled, to 1.44 seconds. While texting, his response time was 1.36 seconds. These figures
correspond to an extra 45 and 41 feet, respectively, before hitting the brakes. His reaction
time after drinking averaged 0.64 second and, by comparison, added only seven feet.”
(Car and Driver, June 25, 2009)
6. Should the laws for texting while driving be as severe as the laws for driving
under the influence of alcohol? Support your position with anatomical and
physiological evidence from your test data in addition to the data above. Discuss
your position and evidence with other members of your group.
From student tests with reaction times, and the Car and Driver data above,
students can give strong evidence that texting and driving is MORE dangerous
that driving under the influence of alcohol. It is interesting to have students
research what the current Minnesota law is regarding cell phone use (talking and
texting) while driving.
Before question #22 the teacher can play the video from:
http://jalopnik.com/5302414/drunk-driving-safer-than-texting-while-driving
**Video may not be appropriate for all audiences due to alcohol consumption**