Summer School - Psych 304 - Interesting Facts

On my last post about my summer course icey posted:

"post some things you've learned if that's legally ok please. behaviour is a very interesting topic."

I have decided to detail some of the interesting things I have learned thus far and don't worry icey, it is legal.

1. Eye Movement

How your brain interprets movement is quite extraordinary. Consider these four cases and try it out for yourself!

1. Both object being viewed and eye are stationary. (Hold out a pencil, is it moving?)
   Result: Object appears to not be moving.
2. Object is stationary but eye is moving. (Scan from the top to the bottom of the pencil, is it moving?)
   Result: Object appears to not be moving.
3. Object is moving down but eye is stationary. (Move pencil downwards while keeping eye focused straight ahead, is it moving?)
   Result: Object appears to be moving.

Now here is where it gets a little bit complicated. Consider case two and three. In both of these the pencil changes its place on the back of the retina. When you move your eyes up the pencil but the pencil is stationary, the retinal image ends up hitting higher on the back of your eye. Yet the same thing occurs when the pencil moves down but your eye stays staring straight ahead (the focus ends up on the eraser in both cases). Why then does your brain interpret one of these as movement and the other as not movement. Well let us make a hypothesis and then test it. Perhaps when your brain moves your eye it subtracts this movement from the change in retinal image and so even though you move your eyes, your brain can tell the world is stationary. How then could we test this? Well try this:

1. Stare off into the distance as far away as possible.
2. Close your right eye.
3. With your left finger gently push on your bottom eyelid to push your eye upwards.
4. Continue to apply pressure, then release it in an alternating pattern.
5. With enough pressure applied you should see the world tilt downwards!

It can be tricky to get this effect to work as people aren't usually comfortable with prodding their own eyeballs. I find that alternating pressure/no pressure helps you to better visualize the downward movement (it can be quite blurry). So what does this mean? Well you tilted your eyeball up, just like you did when you looked at the tip of the pencil. This time though, your brain did not initiate the movement of the eyeball so it was unable to subtract this movement, thus your brain said "The world is tilting down!".

I just realized this does not have much to do with behaviour so I will have to do another post tomorrow about behaviour. Dangit. Hope this is interesting icey!