Sight
Sight is a human's dominant
sense and often taken for granted by most observers, but is still
underdeveloped by most humans. These
activities help campers to more fully understand the eye and comprehend some of
the intricacies of human sight.
Begin by introducing the
tremendous amount of information that humans observe through the eyes. One can challenge the campers to count the
colors around them or to count the different plants that they can see in their
field of vision. Also demonstrate that
information varies with distance. Hold a
leaf fifty feet away from the group of campers and gradually move towards
them. More and more detail will come
into focus at each stage along the way.
Ask how campers think our sight campers with animal's sense of sight in
terms of colors, depth, and detail.
Explore the world of animal
sight by offering simulations of animal eyes.
For instance a pair of cardboard tubes that one can rotate around the
eye can imitate the eyes of chameleons.
Angle eyes, which refocus at a 90 degree angle
simulate deer vision and the variety of animals that have eyes on the sides of
their heads. Kaleidoscopes represent
insects, binoculars for hawks, very near-sighted glasses for rhinoceroses and
so on. Allow the campers to attempt to
move using their new eyes and eventually have them walk to a goal successfully
using their animal eyes.
Show campers why we need two
eyes. The fancy answer is that binocular
vision allows depth perception. The
proof is in the game though. Set up a
target of some kind, a trash can, cone, etc.
Instruct the campers to find a good throwing stick, about an inch in
diameter and a foot long. After they
return, assemble them into a firing line and make them all close or cover their
right eye. One by one the campers should
then throw the stick at the target. The
naturalist must count how many times they actually hit the target. Repeat the activity with the left eye closed
and then with both eyes open. Almost
always, campers hit the target most often with both eyes open, showing that
their ability to judge distance is better with both eyes. Two eyes are better than one.
The question often arises why
the group did better throwing with just the right eye open than with just the
left eye open. The answer lies in the
dominance of one eye in humans. You can
demonstrate this dominance in two ways to your group. Instruct them to point at a distant object,
and then have them close one eye at a time.
When one eye is open the pointer finger should still be pointing at the
object, but it will not be when the other eye is open. In the other method, have the group look at a
distant object and then make a triangle around it using both thumbs and pointer
fingers. The triangle should initially
be at arm length. Gradually bring the
triangle towards the face, and the triangle will naturally move in front of the
dominant eye. According to my
optometrist 70% of humans are right eye dominant, and the other 30% obviously
left eye dominant. Those statistics seem
to hold up with my campers at Kirchenwald.
Another remarkable activity
with the eye is to show campers their blind spot. The nerves of the eye are set up in such a
way that an area very near the face does not receive any sight impulses. Use the below figure on flash cards and have
the campers start by looking at the dot while holding it directly in front of
one eye, about ten inches from their face.
Move the card slowly toward the face and eventually the cross should
disappear when it enters the blind spot.
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