s+p exam 4 pt 7!

pulfrich pendulum illusuon

a type of motion illusuon

• think about the activity we did in class with the pendulum and the filter- the darker the filter, the better it worked– it should look like its going in an oval. the picture: left to right motion and right to left motion. The pendulum is the horizontal straight line is the depiction of the pendukum going back and forth, when we put the dark glass filter, it slows down the light, so now the left eye is getting delayed signals (as shown in the graph– its taking a longer time to get to the eye), so the right eye is seeing the pendulum sooner, and because of steropsis, we are combining the two and we are getting an inbetween of the delayed and normal speed. We get an oval shape because the pendulum is going to fastest when it is swinging downwards (the effect is the largest when its going fastest). So it shows us: 1. That the brain combines images from both eyes (steopsis) 2. We can also slow down perception (once the signals get in (we don’t get this w sung;lasses because it’s w both eyes, so they;re both getting delayed evenly), so we get the oval when we combine the two halves, take away the filter and we just get the single plane of back and forth.

what is motion perception?

• All about perceiving events vs perceiving an object: an object occurs inn the space domain (height, width, depth), and event is the same, but involves movement or motion (its in the space AND time domain) → if we’re just looking at someone and they’re standing still they’re an object, but if they’re moving, they’re in event)

• The problem: there’s ambiguity from the eyes (an ambiguous reintal image)

The ambiguous reintal image:

object is moving from left to right (in A on the left the square in the eye starts on one side of the eye and moves over to the other– the second one (b): you’re fixating and focusing on the  finger as it moves and it is staying on your fovea, so that object stays on the fovea if the eye is moving back and forth → basically on the left if theres movement on the retina, theres movement of the object, on the right: if theres no movement on the retina, theres still movement of the object.

what did gregory propose?

2 types of seperate systems that could signal motion:

1. Image-retina system: motion is perceived when the eye is stable and the image is moving on the retina, we get motion (object is sweeping across the back of the retina in one direction or the other)

2. Eye head system: if you have a moving eye but have a stable image on the fovea, that too should be percieved as motion

The corollary discharge theory:

when you move your eyes, there is a signal from the motor part of the brain that tells the eye muscles to move (this is the motor signal), a copy of that signal is snet to the comparator (think of the copy of the recioprt someone has written) it is going to take a copy and compare it to the image motion signals coming from the retina so now the comparator compares the CDS and IMS and sends its results to the sensory part of the brain 

what is the rule about the comparator

if the CDS does not cancel out (or equal) the IMS, then motion is perceived (another way of saying this: if what we expect does not occur, then the motion is perceived) 

why doesn’t the world jump when our eyes move?

why can’t we tickle ourselves→ because we know it’s coming, and we expect it (he told us to look from one corner to the other and we initiated the eye movement, so we knew it was coming, this is explained by the corollary discharge theory.