Need help explaining interposition (occlusion) and relative size for my perception class...

[BigToquex]

I'm supposed to give a speech (about 5 minutes) describing interposition and relative size. I should also try to relate it to impossible figures.

I've read a whole wack of stuff, I just dont know exactly what to say and tie it all together...

Any ideas?

I know that they are both depth cues.
I know that interposition works by partially overlapping another object.
I know that objects get smaller as distance from that object increases.

I just dont know how to expand...

 

[BigToquex]

I know its soon for a bump, but I really need some ideas...

I've got 2.5 hours left

 

[EngenZerO]

find a generaly psyhcology book and eloborate.