Expert: Kai Schreiber - 10/2/2007

Question
Hello Kai,

Thanks for your reply on the number of neurons in our brains.  I guess its best not to pigeon hole our capacity by  throwing numbers around.

A question on vision and the brain.  What proportion of the brain's function is devoted to vision?  I'm asking because I suspect its high, a quarter, a third of the brain?  Yet birds with their tiny brain have excellent visual acuity and recognition, so why do we have so much brain of our brain devoted to sight when a little is all that is needed?

Thanks.
Regards,
Usuff

Answer
Hi Usuff,

you're about right there, the number usually given indeed is somewhere between a quarter and a third of neocortex being devoted to vision in humans. This is a lot, both relative to brain size and in terms of absolute number of neurons and mass of brain involved.

But while it is true that small animals get by with much less, the demands on their sensory systems are also much simpler. We are very good at recognizing and distinguishing fairly subtle patterns, quickly decoding printed pages, for example, or distinguish between trees based on the pattern of their leaves or bark. We accomplish this by having a very flexible and powerful visual system.

Animals, on the other hand, are usually quite specialized to the tasks and stimuli that are important for them, and can get by with much simpler systems, that then can actually surpass our own for their specific task.

Best,
Kai