Brains and Computers
The interesting aspect of this question, and what makes it so difficult to answer, is that we know so little about how the brain works. We have compared the human brain to computers for decades, but how the human brain works as fast as it does is a mystery. It is also difficult to define what we are comparing. The brain processes visual information much faster than any computer, but is very slow at calculating mathematics. However, the brain seems to be superior at simultaneously processing huge amounts of vastly different information.
For example, as I am writing this my brain is processing all sorts of sensory information the sensation of sun on my body, the feel of the computer on my lap, the lingering taste of Gatorade, the sounds of Bruce Springsteen (and all his social and political messages) in my earphones, as well as the quiet rush of the breeze, and the smell of the desert. Lets not forget all the somatic housekeeping, like breathing heartbeat and digestion. For more years than I will admit, my brain has been directing those activities as well, 24/7/365. In addition to all that, the cognitive center of my brain is composing the ideas and associations then translating them into symbolic language, and sending them to the keyboard via motor instructions to my fingers. As you read these words, coherent thoughts are transmitted from my brain to yours, and you can hear the voice of my brain speaking in yours. Amazing stuff.
That is an incredible amount of processing, all done by a three-pound lump of tissue small enough to fit inside my skull. If one were to get enough computers together in one place or access the US Treasury to pay for one super computer most of those tasks might be completed, but with tons more hardware, and a lot more watts. Even so, there would be no creativity or personality. The associations between one and idea and another made in my brain are unique products of my personal experience, the way those experiences are stored, and the way they are recalled. We do not seem to know exactly how the brain manages all that. Moreover, computers are not conscious. Whatever is that makes a human mind, (as opposed to a brain), would be missing. There would be no sense of self or individuality. At least we do not think so. Dan Dennett does a good job of exploring machine consciousness or lack of it -- at KurweilAI.net (Dennett 1997).
Something I find interesting is the sudden explosion of pre-human intelligence several million years ago. In Dragons of Eden, Carl Sagan (1977) speculates that it may not be brain volume or size that matters, but the quality of brain functioning. Neanderthals had brains larger than ours, as did Cro-Magnons, and all were alive at about the same time, yet Homo sapiens were the only one to survive. This implies that there was some superior quality about man that other species did not posses, in spite of their slightly larger brain volume, and superior physique.
Carl Sagan tells us that after millions of years of incremental improvements there was a sudden expansion of human creativity and insight in the Precambrian period. It seems that brain volume reached a point that made foresight possible, and with it concepts of death, aging and wisdom. This was not a gradual process, but a sudden occurrence. It is as if a line had been crossed that allowed even faster evolutionary development.
Sagan tells us about Sir Arthur Keith and his idea of a Rubicon of brain development. Keith proposed that a particular size of brain allowed a quantum increase in intelligence. Cranial volume of 700 cubic centimeters might not be enough for language development, but 800 might do the trick.
Could there be a Rubicon, not of size, but of quality, Sagan suggests. Is it possible that that brainpower is not simply a matter of brute processing power, but rather of the quality of the processing? The skulls of Neanderthals are shaped differently than human skulls. Neanderthals skulls are longer, (anterior/posterior), while human skulls are higher, (dorsal/ventral). Might it be possible that the internal structures of the brain are different as well? Neanderthals might well have had more highly developed forebrain structures than humans, but been at a disadvantage without the well-developed neo-cortex of humans.
However, brain shape and size might not be as important as other structures. It is impossible to know what the brain structures of pre-humans actually looked like, so we have no idea exactly what structures, or combinations of structures, gave evolutionary advantage to humans. We can guess that language, and the related development of cooperation, social structures and empathy have a symbiotic relationship with intelligence. Each of these things depends on the others, yet also compliments them, and presumably accelerates their evolutionary development.
One of the symbiotic relationships that seem to have accelerated humans along the path of evolutionary intelligence seems to have been the ability to make and use tools. Tools lead to mechanical devices, simple machines eventually leads to complex technology. Each step along the way requires and supports increasingly sophisticated styles of thinking. Without the ability to manipulate naturally available raw materials into tools, and then manipulate tools into useful items nothing much would evolve.
However, brain structure is not the only thing that contributes to intelligence and technological societies. Seth Shostak (1998) makes an interesting argument about the importance of thumbs to human intellectual development. Like humans, whales are very intelligent, have complex communication systems, and highly sophisticated social organization, yet have not developed anything like the social technological or intellectual accomplishments that humans have. Shostak wonders if this has something to do with lack of hands, fingers and especially thumbs.
Are whales an example of intelligence limited by the lack of challenges that fingers, thumbs and hands can provide? Is human intelligence the product not just of natural selection, but the sort of natural selection that results in challenges that spark symbiotic systems and the development of a particular balance of intellectual abilities?
Why is it so difficult to compare brains and computers?
Maybe looking for similarities between computers and the human brain is so difficult because our concept of a computer is fundamentally different from the brain. I am not convinced that the brain is analogous to a binary computer. Maybe quantum computing will make such comparisons easier because our brain is not really a binary computer, but rather a quantum computer.
But that rises more challenges. Simply unraveling the abstractions of quantum physics is difficult for most of us to wrap our brains around. How can a particle be a 0, a 1, and something in between, all of them simultaneously? It makes my brain hurt just to think about thinking about it. However, that might be the conceptual environment in which we need to think about similarities between the human brain and computers.
What a great time to study psychology!
Dennett, D. (1997). Consciousness in human and robot minds. KurzeilAI.net. Accessed from: http://www.kurzweilai.net/meme/frame.html?main=/articles/art0474.html
Sagan, Carl, .(1977). Dragons of Eden. New York, NY: Ballanatine.
Shostak, .(1998). Sharing the Universe. Berkley, CA: Berkley Hills Books.