The differences between brains and computers

Computers have become such an integral part of life that it's often tempting to believe that they work just like the human brain (or that the brain works just like a computer). However, those of us who've spent time programming computers know that we don't "think" like computers: if we did, a single misplaced semicolon could turn Hamlet into meaningless babble.

Chris Chatham has developed an excellent list of 10 differences between brains and computers. I think the difference that best illustrates the programmer's dilemma is Number 2:

Difference # 2: The brain uses content-addressable memory

In computers, information in memory is accessed by polling its precise memory address. This is known as byte-addressable memory. In contrast, the brain uses content-addressable memory, such that information can be accessed in memory through "spreading activation" from closely related concepts. For example, thinking of the word "fox" may automatically spread activation to memories related to other clever animals, fox-hunting horseback riders, or attractive members of the opposite sex.

Computers don't instantly make this type of association: if the precise memory address isn't given to the computer, it's never going to find the item you're looking for. But how come computers can recommend the correct spelling of a word when you make a typo? Isn't that an example of a computer "associating" one memory with another? Not exactly -- these associations have been painstakingly programmed in to the computer. Somewhere in the computer there's a list of common typos, along with an algorithm for pulling recommendations from a very precise database of correctly spelled words.

Another one of my favorite differences:

Difference # 10: Brains have bodies

This is not as trivial as it might seem: it turns out that the brain takes surprising advantage of the fact that it has a body at its disposal. For example, despite your intuitive feeling that you could close your eyes and know the locations of objects around you, a series of experiments in the field of change blindness has shown that our visual memories are actually quite sparse. In this case, the brain is "offloading" its memory requirements to the environment in which it exists: why bother remembering the location of objects when a quick glance will suffice? A surprising set of experiments by Jeremy Wolfe has shown that even after being asked hundreds of times which simple geometrical shapes are displayed on a computer screen, human subjects continue to answer those questions by gaze rather than rote memory. A wide variety of evidence from other domains suggests that we are only beginning to understand the importance of embodiment in information processing.

For more on change blindness, see here, here, and here.

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By Alan Williams (not verified) on 07 Apr 2007 #permalink