Over at Scientific American, a reader wonders about the memory capacity of the human brain. According to Dr. Paul Reber, professor of psychology at Northwestern University, the answer is about 2.5 petabytes, with the following rationale:
The human brain consists of about one billion neurons. Each neuron forms about 1,000 connections to other neurons, amounting to more than a trillion connections. If each neuron could only help store a single memory, running out of space would be a problem. You might have only a few gigabytes of storage space, similar to the space in an iPod or a USB flash drive. Yet neurons combine so that each one helps with many memories at a time, exponentially increasing the brain’s memory storage capacity to something closer to around 2.5 petabytes (or a million gigabytes). For comparison, if your brain worked like a digital video recorder in a television, 2.5 petabytes would be enough to hold three million hours of TV shows. You would have to leave the TV running continuously for more than 300 years to use up all that storage.
I’m not quite sure why the professor claims that 2.5 petabytes is equivalent to one million gigabytes – unless I’m mistaken, it should be equivalent to about 2.6 million gigs.
Of course the nature of memory is fluid. Most memories degrade with time – become “fuzzy” – or can disappear altogether. On the other hand, occasionally we can be reminded of an event that took place in our pasts and recall a vivid memory that we’d “forgotten.”
Putting the estimated capacity of the brain in terms of petabytes, a measure of digital information, is a bit problematic, since the human brain is analog (although there is some debate on this point). Furthermore, Dr. Reber notes that we have no way to accurately measure the size of memories, so putting a number on the brain’s memory capacity doesn’t necessarily tell us a great deal.
(Via Neatorama)