Teacher Pages

Getting Disoriented Studet Pages

California State Standards addressed: Grade Nine - Twelve: Physiology	Subsections: Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment. Students know how feedback loops in the nervous and endocrine systems regulate conditions in the body.

KEY: Can't find an exhibit or have a question? Ask an explainer Refers to the exhibit graphics and the instructions in them Refers to things to do not suggested in the instructions on the exhibit

Normally we trust our senses, but sometimes we can't - and this is the most disorienting thing of all... Our bodies have mechanisms to tell us if we're right side up or upside down, moving or standing still, or looking at or hearing something near to us or far away. But as you'll find out along this Pathway, our bodies can also be fooled. There are lots of things that disorient or unbalance people- for example: heights, ocean voyages, mirrors, fevers, or being underwater. How do you keep balance? What do you rely on to do this? What things put you off balance? When is it hard to stay balanced? What's your definition of an illusion?

Cross-Reference Entry Are you sure you know when you're moving and when you're standing still? Make sure your friend holds the wall perfectly still for the time you're standing on one leg. And that they then move the wall very slowly and evenly in one direction. What happened? It becomes very difficult to maintain your balance. Try it again. Did the same thing happen? If not, how was it different? It might be easier to keep your balance the second time around. Why? Because you have learned to pay less attention to visual information to keep your balance and more attention to other sensory information, such as feeling your weight on your foot.

In this exhibit, you learn to do something difficult, and then you have to "unlearn" it in order to do something easy! With the prism goggles on, how many throws does it take you to make a basket? Anywhere from one to ten throws. After making fifteen shots with the goggles on, take them off and try a shot. How many throws does it take with the goggles off? Some people can do this immediately! But for most people it takes a few throws to get used to seeing "normally" again. You can repeat this experiment but this time try throwing with your other arm after you take the goggles off- that arm isn't "trained" like the other one. What happens? Many people find it difficult at first to make a shot with the other arm.

Associated Snack Cross-Reference Entry With this exhibit, you can practice being a figure skater, an astronaut, or going on amusement park rides without getting sick! What happens when you extend your arm or leg while spinning? You slow down. What happens when you bring them back in? You speed up again. Ballet dancers use a method called "spotting," where they keep their eyes trained on a certain spot while spinning around. Their head "lags behind" the rest of their body for half of the spin, and then they quickly turn their head, stopping to focus on the exact same spot again and again. 1. Does this work for you? Some people will be able to do this quickly, but for most it takes a good deal of practice. If you want to avoid nausea (you can't really avoid dizziness though!), whatever you do, don't tilt your head up and down or keep your chin pointed at your chest as you're spinning! Closing your eyes is probably a bad idea too- you'll get conflicting signals from your eye and the semicircular canals in your ear (see below). Do you get queasy while reading on the bus? Same effect. A part of your inner ear called the semicircular canals contains a fluid, called endolymph, that flows over nerve endings and informs you of changes in your body's movement. Spinning around sets this fluid spinning too and it's own momentum keeps it moving even after you've stopped. You'll probably feel dizzy while you're waiting for it to settle down. These canals also help tell you which way your body is oriented, much like the fluid in a carpenter‚s level. If your head is tilted while the fluid is sloshing around, this mechanism sends the signal to your brain that you are not upright- but your own eyes contradict this! This contradiction tends to make people nauseous.   After spinning fast, get off the machine and try walking in a straight line (you can ask your friend to judge). 2. Can you do it? Did you experience a slight feeling of loss of control? Most people cannot walk in a straight line if they've spun long enough.

Associated Snack Cross-Reference Entry Your "eye-brain" system has built-in detectors of inward and outward motion. If one detector gets tired, as when you stare at the pattern, the other one can override it when you look at something stationary, and even objects standing still appear to move towards or away from you. What's the connection between how the spirals appear to move and how the wall appears to move afterward? If the spiral appears to move inward (toward the center), things appear to move away from you when you look away. And vice versa.

Associated Snack Cross-Reference Entry Sometimes your brain alone makes things move. What is the same about this exhibit and Depth Spinner? Both exhibits cause you to "see" something that is not really happening as a result of your attention to the spinning disk. What is different? Depth Spinner causes a sensation of inward or outward motion, while Squirming Palm gives the sensation of something spinning around.

Cross-Reference Entry Why does that big tree in the distance seem to be no bigger than my finger? Try touching the two bent rods together. When looking through the prisms, did your perception turn out to be different from reality? How? Most people have difficulty knowing exactly how far away the bent rods are from their eyes, thus making it difficult to make the two rods touch each other. Can you use your brain to make perception and reality match? Yes- once you do make the two rods touch, you have a memory of that and as you repeat the experiment your perception begins to match the physical reality. Make one of the rods pass in front of the other. How does this affect the illusion? It breaks it by allowing you to see which rod is in front and which one is behind. Is there anything else that "breaks" the illusion? Yes- you can look at the two rods from above. This way you can tell immediately which one is in front and which one is behind - for example.

Associated Snack Cross-Reference Entry We're better at seeing something moving than we are at seeing something standing still.   Describe what happens to your friend's face. Part or all of it disappears! Your eye-brain "prefers" a moving object to something standing still, so you'll notice the motion of your hand at the expense of seeing your friend's face. If the movement of one of your hands can make all or part of the image disappear, the eye corresponding to that hand is likely your dominant eye. Which is your dominant eye? For further experiments with similar aspects of your vision, check out the exhibits Two as One, Motion Detection, and Peripheral Vision. What's the connection among these exhibits? Two as One uses your binocular vision to combine two separate images, one seen by your left eye and one seen by your right eye, into one image. Motion Detection and Peripheral Vision demonstrate another parameter of our vision, peripheral vision, and our strong sensitivity to motion, even at the outer edges of our field of vision.

Cross-Reference Entry When we think in three dimensions, the power of our imagination can be a startling thing. Putting the dark plastic over one eye can delay its vision slightly. What is the effect on you? For many people, the shadows seem to change direction- a shadow that seemed to be moving toward you starts to move away from you, and vice versa. Some people can make the shadows switch direction just by thinking about it! Can you?

Associated Snack Cross-Reference Entry The spring really is in the box somewhere! But what you see is a very good reflection. Where IS the spring, actually? The actual spring is hanging down just under the hole in the box (you can reach it with your hand). Why does the reflection appear to have a shadow when you shine the light on it? If you follow the path of the light on a parabolic mirror, you'll find that the light you shine on the image does actually reach the spring, casting a shadow that is then reflected back to your eye.

Associated Snack Cross-Reference Entry Don't get fooled again. What is the key to the illusion? Another parabolic mirror. Try putting other objects where the key really is. Try your hand. What happens? You see those objects where you first saw the key. Where else have you seen an illusion like this? Touch the Spring.

Associated Snack Cross-Reference Entry Looking in a mirror can really make you forget yourself. What happens when you move the hand you can't see? It seems strange that you don't see the hand in the mirror moving, especially after recently moving the two hands together. Our two hands are more or less mirror images of each other, so replacing the sight of our real hand with a mirror image is confusing! Have a friend put their hands on the bar, one on each side of the mirror. Make sure they are only looking at one side. Now, put your index fingers on the back of each hand, and slide them along in an even, parallel motion. Do this several times, and then without warning remove the finger from the hand that your friend can see, while continuing on the hand they cannot see. Have them do the same for you. Describe what you feel. One typical answer: strange. See "Read and Do" above.

Is this how dolphins see the world? What is it like to see your hand underwater? Does it look wet? It actually appears dry. Try to catch some air in your palm. What does it look like? Many say it looks like you're holding some mercury, or quicksilver, in your palm. In any case, it becomes clear that air is a something, and not a nothing.

Cross-Reference Entry Heavy things can come in small packages, and vice versa… What do you think makes it difficult to guess correctly? We have a tendency to think that bigger means heavier. But we also have a tendency to mistake density for weight- the small metal object exerts a greater force per unit area on our hands (pressure), and many people misinterpret this sensation and guess that the metal weight is heavier. What is the difference between density and weight? Weight is the mass of an object (measured in kilograms) times the force of gravity. This is how heavy an object is. Density is the mass of an object divided by its volume. this is how "concentrated" an object is.