Quick Question about the Sperry amphibian eyeball experiment.

Ok, so if you are reading this I'm guessing you know that a chap called sperry chopped the optic nerves of a frog to see if they regenerate faithfully to there origonal position in the optic tectum.

They do and the frog now sees everything upside down and back to front.

I understand all of that but what I cannot fathom is the fact that if an object was infront of the frog it ran away thinking it was behind it? Why does it do this. I asked my lecturer to explain and he dd but I still didn't get it and I think he was about to kill me for pestering him!

So why the behind / infront reversal?

cheers Jack