Why we see Erect and Same Sized Image?

Most recent answer: 01/18/2015

Q:
why we see erect and same sized image if the image formed on retina is real and inverted?
- saily samanta (age 13)
bhubaneswar,orissa , india
A:

You are absolutely right regarding the fact that your eyeballs are actually pinhole cameras. Therefore the image on the retina will be inverted: not only upside down, but also left-right! But this is only the sensory part. Visual perception is a result of processing in your brain, mainly a part called visual cortex. Your brain is wired in a way to account for this abnormality, so what you perceive is erect. Although our knowledge about the functioning of the brain is still not quite sufficient, such effects can be experimentally demonstrated by changing the wiring (say, by manipulationg your nerves between eyes and the brain).

But the size concept is not straightforward. We perceive sizes by making comparisons to the other objects around us and this what is behind many illusions that you hear about. A typical example of this is the lunar size illusion: the moon appears bigger when it is closer to the horizon, alhough its diameter can be astronomically measured and it is the same!

Tunc


(published on 01/18/2015)