Reliability Of Your Visual Sense

William M. Gordon              Parkman Elementary School
                               241 W. 51st Street
                               Chicago IL 60609
                               (312) 535-2220

Objectives:

Students will:

     (a) perform a series of tests on the reliability of their visual sense.
     (b) record their observations for each test.
     (c) conclude from their data how reliable their visual sense is.

Materials needed:

colored pencils or crayons:        lightweight cardboard
 (yellow, green, red, black)       glue
white unlined paper                straight pin
pencil with eraser                 3 x 5 file card 
protractor                         ruler
paper clip opened

Strategy:

Activity A. Afterimages

(1) With colored pencils or crayons, color the four squares.  Use only the color 
indicated for each square.

(2) Stare at the cross in the center of the colored squares for 30 seconds.

(3) Then, stare at a white unlined sheet of paper.

(4) Observe the colors that appear on the white paper and the position of each 
colored square.

(5) Closing your eyes for one or two seconds while staring at the white paper 
will help intensify the colors or cause them to remain visible for a longer 
period of time.

(6) Repeat the previous three steps as many times as necessary in order to 
identify each color and its location.

(7) Record the color appearing for each colored square.

Activity B. Color Wheel

(1) Cut out disk and glue it to thin cardboard.  Trim the cardboard around the 
disk, and with a pen, attach the disk to a pencil eraser.
 
(2) Spin the disk in one direction by striking the disk's edge with your finger 
as rapidly as possible.

(3) Note the appearance of colored bands.  Record the specific color bands and 
location of each band.

(4) Spin the disk in the opposite direction and again note and record the colors 
and location of each band.

Activity C. Ambiguous Figures

(1) Look at the ambiguous figure.  Determine whether you see a series of cubes 
piled on top of each other toward the left side or toward the right side.

(2) Look again at the diagram; look continuously for at least 30 seconds.

(3) Record your observations.
 
Activity D. Seeing Backwards

(1) With a pin, punch a hole in the center of a file card.
                                  
(2) Look through the pinhole with one eye while holding the card about 5 cm from 
your eye.  Look toward a light source (windows or ceiling lights).

(3) Slowly pass an opened paper clip from left to right in front of the pinhole 
between your eye and the card.  Hold the paper clip as close to your eye as 
possible.

(4) Look for the shadow of the clip to appear through the pinhole.

(5) Note the direction the clip shadow moves as you move the clip from left to 
right.

(6) Repeat the previous three steps but now move the clip from right to left. 
Note the direction of the clip shadow as you move the clip up and down.

(7) Record your observations.

Analysis:

     Write a brief report which explains whether or not your visual sense is 
100% reliable.  Draw conclusions about the reliability of your vision from the 
investigations performed and from other investigations with which you are 
familiar.