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Psych 2115 nov 6.docx

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Psychology 2115A/B

Psych 2115 Nov 6 Two systems that have to be integrated 1. Image retina system: keeps track of what the images are as they're on your retina (what's going on with images on your retina) 2. Eye head system: keeping track of where the eye or head is moving to. Get info from both these systems and integrate them to produce an ultimate perception. Image retina system is very sensitive. You can detect motion on your retina (eyes aren’t moving, heads aren’t moving) with a threshold as low as .03 degrees of visual angle per second (it would take 33 seconds to cross your thumb nail - this is very slow) you have the ability to perceive movement at that level. A gven cell will respond to motion in a particular way and these are the cells that will respond to motion across your retina (specialized cells for certain types of motion) Waterfall illusion, the spiral motion aftereffect How does the brain know what the eye is doing? How does it know wht direction the eye is moving and to take that into account. The eye muscles tell the brain what they’ve just done- this is know as "inflow theory" (Sherrington?) Helmholtz said that he thought the reason the brain knows where the eye is is because the brain ordered them to move How do you run an experiment between these two theories? Hard to find a situation where only one piece of information is there/ accurate, look for a situation where one piece of info is accurate and one is inaccurate. If they see the world accurately, they are using the accurate information. Push your eye and it looks like the world moves; what does this prove? Inflow information from eye muscles going into brain is accurate, when you push your eye the muscles know they're being tugged on, not cause they were asked to because they were forced to, and they sent up the info to the brain. The outflow information is not accurate because the brain didn't send a command to the eyes to do anything, therefore the outflow information was "stay put", but the eyes did go somewhere. You inaccurately perceive the world- you weren’t moving when your eye was being pushed, but you perceive things as moving, so your perception was inaccuarate, so to produce an inaccurate perceptuon you must have used inaccurate information, which was the outflow information. (outflow info- info brain is giving to eye muscles) Exp: someone with a contact lense with a little rod sticking out that has a string on it, you can't see the string, someone pulls the string to make your eyes move in a different direction, the eye muscles give accurate inflow information to the brain (tell the brain what is really going on), outflow information is inaccurate because it didn’t tell them to move. How do you perceive the world? You perceive the world as moving across your retina, your perception is that the world is in motion. You are using inaccurate information, and the outflow information is what is inaccurate, so you are using outflow information. Exp: create a situation with accurate inflow information and inaccurate outflow information, and therefore inaccurate perception. Anesthetize the nerve between the brain and the eyes, so if your brain tells your eyes to do something the eyes don’t get the command, tell the person to move their eyes to the right, the person can't make their eyes do this so the eyes don’t move. The brain thinks the eyes are moving to the right, but the eye muscles tell the brain they are not moving. Accurate inflow (the eye muscles know nothing happened) and inaccurate outflow (the brain told the eyes to move and thus thinks they moved). You think the world has moved with your eyes, but your eye didn’t move so the world didn’t move, so you have the wrong perception. Autokinetic effect: stare at a blank screen with a dot in the middle of it, instructed to look at the dot, after a while people report that the dot has started to move. Your eye moves in discrete jumps and that’s one kind of movement, your eyes can also move as a "smooth pursuit" but they need something to latch on to and follow, theres a third kind of motion where your eyes drift and that’s what's happening
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