Module: Visual Perception

Straight Ahead

Grades K-6


Activity created by: Brenda LeBeck
Principal Investigator: Dr. Mal Cohen

Overview

One of the most basic daily actions is to move your body from place to place. But how does your brain know that you are going the right direction? In this activity students conduct experiments to determine how a person's ability to walk on a line is affected by conditions that confuse the sense organs needed to navigate.

Space scientists are working to understand more completely how the brain gathers and analyzes information it receives from receptors in the eyes, ears, and muscles of the body. In space, where conditions are different than normal on Earth, the brain can experience confusion as it tries to direct the body's movements. This confusion can lead to disastrous consequences for astronauts and their mission. By understanding how the brain uses information it receives from the body's sense organs, researchers may help astronauts adapt to conditions in space and prevent potential life and mission threatening mistakes.

Key Questions

What information does your brain use to direct your body as you walk?
How are the speed and accuracy of your movements affected when conditions are different than normal?

Time frame

Preparation: 20 minutes

Conducting the experiments: Three 40 minute class periods

Discussing the results of the experiment: 20 minutes

Materials

For the whole class:

1 roll of masking tape
1 ruler or measuring tape
optional: 1 transparency of the "Straight Ahead" data sheet (master for photocopy on following page)

For each group of 10 students:

1 blindfold
1 stopwatch
1 meter stick or metric measuring tape
1 clipboard (optional)

For each student:

Getting Ready

1. Review the section "Background for Teachers" at the end of this document

2. Prepare the experimental area. Use the masking tape to make a straight, 6 meter (20') lines for each group of ten students. (Optional: If the experiment will be conducted outside, you can make chalk lines, or use painted playground lines instead of masking tape.

3. Plan to divide students into groups of 10. Optional: assign each student to a partner.

4. Assemble the rest of the materials listed above.

5. Optional: For younger groups, arrange for adult volunteers to assist.

Classroom Activity

1. How do you know where you're walking? Invite a student to stand in front of the class and walk along the tape line. Ask, "How does this student know where to walk?" Accept responses. Give an example, "She can see where she is going. Is there any other way she can know where she is walking? Suppose she could not see, would she still be able to stay on the line? How would she know how to stay on the line even when he couldn't see it?" Accept responses.

Explain that in addition to information from the eyes, the brain uses information from other sense organs in order to monitor its movement. Your inner ear, inside your head, has fluid that shifts when you move. This organ tells your brain if your head or body is tilted and if you are moving. Also, every muscle in your body has sensors (nerves) that tell your brain how your body is positioned. As you move, the brain combines the signals it receives from all over the body and uses them to make adjustments as you move. In this experiment you will study the role each of these body systems play in helping your brain know where you are walking.

2. Walking the straight and narrow. Invite one pair of students to the front of the class. Explain that one student will be the test subject and direct that student to stand at one end of the line. The other student will be the timer and data recorder. Give the timer/recorder a stopwatch, clipboard with data sheet #1, and pencil and ask them to write the test subject's name in the appropriate place on the data sheet. When you are ready say, 'Go!' and turn on the stopwatch. When the test subject hears the signal she walks to the other end of the line. When she reaches the other end of the line, click the stopwatch off and write down the number of seconds it took for her to walk the line. Have the pair of students conduct the experiment as a demonstration. To determine accuracy, give a meter stick to the data recorder and have her measure the number of centimeters between the line and the closest edge of the test subject's heel when she finishes walking the line. Have them record the time as well as accuracy.

(For younger students: Use two parallel tape lines 50 cm (20") apart. Mark the tape every 20 cm (or every foot). Instead of timing the experiment and measuring accuracy, students can record number of marks the test subject passes before they step outside the tape lines.)

(For older students: Brainstorm ideas for determining accuracy in this experiment. Decide as a class which method will be used for your experiments.)

3. Conduct the experiment (control). Ask students to line up in groups of ten at the starting point of each tape line. One pair of students conducts the experiment at each line. After one student in the pair participates as test subject, then roles are switched and that student becomes timer/recorder for their partner who is the next test subject.

4. Experiment with limited vision. (Use Data Sheet #1.) Explain that special nerve cells inside the eye carry information about light they sense to the brain. Ask, "How can we change the conditions of our experiment so your brain is not able to receive information from your eyes?" Accept responses. Suggest using blindfolds for test subjects. Ask the class to conduct the experiment again, with test subjects blindfolded.

5. Experiment with limited vision and mixed signals from the inner ear (after spinning in circles). (Use Data Sheet #2.) Explain how sensors of the inner ear send signals to your brain about the position of your head and the direction your head is moving with respect to Earth's gravity. Suggest that by spinning around in a circle, students may confuse their brain's understanding of where the ground is in relation to the body. Ask, "How do you think spinning in circles will affect your ability to walk the line?" Accept responses. Allow time for students to conduct the experiment, after the test subject, blindfolded, has spun in place for 10 seconds. (There should be about 5 spins in 10 seconds.)

6. Experiment with limited vision and mixed signals from sensors in skeletal muscles. (Use Data Sheet #3.) Explain how nerve cells in every muscle of your body send information to your brain about how the parts of your body are position with respect to the rest of your body. Suggest the following procedure for tricking your brain about the position of your body, "While blindfolded, or with eyes closed, lift your left leg and arm for 12 minutes. Then conduct the experiment to see how this affects your ability to walk the line quickly and accurately." Before allowing time to conduct the experiment, ask, "How do you think lifting your left leg and arm will affect your ability to walk the line?" Accept predictions. Allow time for students to conduct the experiment.

Wrap-up Session

1. Help students to analyze and discuss data they collect. How were speed and accuracy affected in each experiment? Did the experiment turn out the way your predicted? Did all test subjects have the same results for each experiment?

2. Discuss the notes made by test subjects after each experiment. Were there any similarities and/or differences between the comments made by different students?

3. Relate the disorientation that the students experienced with the disorientation astronauts experience in space. What are some ideas that students have to help NASA train humans for space travel?

More Activity Ideas:

1. Conduct the "Straight Ahead" experiment under a variety of conditions. Ask the class to brainstorm ideas for creating conditions that confuse the brain about the signals it receives from the eyes, inner ear, and muscles of the body. Here are some examples for further study:

Vision-conduct the experiment after wearing a blindfold for 15 seconds or longer. Does wearing the blindfold for longer periods before the start of the experiment affect the student's performance?

Spinning/inner ear-How do the direction and rate of spinning affect the experimental results? Does spinning affect the test subject's performance when the experiment is conducted without a blindfold? Conduct the experiment with the subject keeping his/her ear pressed to their shoulder or with their head tilted way back.

Muscular activities-How does lifting the right leg and arm change the results compared to the experiment conducted after the left leg and arm were lifted? Does lifting one leg and arm affect the results when the subject is not blindfolded? Have the test subject wear wrist and ankle weights on one or both sides. How does this affect the experiment? What are the results when the subject must hop on one leg, wear only one shoe. or walk backwards during the experiment?

2. Brainstorm and discuss scenarios in which your visual, balance, and/or muscle sensors send confusing signals to your brain. Think of situations both on Earth and in space where misperception could occur. Discuss consequences of this misperception. Ask students to write a short story describing a situation where misperception occurs and the consequences of that misperception.

Background for Teachers

Prerequisites:

Students must be able to:

walk a relatively straight line
use a stopwatch (for older groups)
measure distance with a meter stick
record information on a data sheet.

Vocabulary:

disorient-To confuse a person and make him lose his bearings.
oculomotor sense-Our ability to sense the position of our eyes and tension in our eye muscles. (Goldstein, Bruce E., Sensation and Perception. Belmont, CA: Wadsworth Publishing Company. 1989)
proprioceptors-Provide the central nervous system with information about the position of the body as well as the information it requires to modify and coordinate motor activity. The receptors in our muscles and joints help us sense the position of our limbs. (Cohen, Malcolm M. Visual-Proprioceptive Interactions. In Richard D. Walk & Herbert L. Pick, Jr., editors; Intersensory Perception and Sensory Integration , pp. 175-215. Plenum Publishing Corporation. 1981.)
vestibular system-helps to maintain posture, balance, and equilibrium to determine spatial orientation and to control eye movements during locomotion to maintain clear vision. The vestibular system consists of two highly specialized organs: the semicircular canals and the otolith organs. The otolith organs, comprised of the utricle and saccule, are particularly sensitive to linear accelerations such as movement of the head forward or backward, left or right, and up or down The semicircular canals seem particularly sensitive to angular, or rotational movements of the head. The vestibular proprioceptors, located in the inner ears, provide information concerning the orientation of the head relative to gravitational-inertial space. Hair cells are the basic functional unit and are stimulated by head movements and by inertial forces such as gravity. (Cohen, Malcolm M. ibid.)

Skills:

collecting, recording and analyzing data
balance and accuracy in walking on a line
understanding and using the scientific method.

Concepts:

The brain collects information from various receptors throughout the body. This information gives the brain a continual sense of how the body is positioned in space around it. Conditions in space can cause the brain to be misinformed-informed by the body's sensors. This misinformation-information can lead to misperceptions that may decrease astronauts performance. Through experimentation, researchers at NASA hope to better understand how the brain collects information about the outside world. This better understanding will hopefully help astronauts maintain high performance levels when asked to do tasks while in space.

Editing by: Gregory Steerman, Alan Gould, Lawrence Hall of Science