Computational capabilities of the human brain

Much interest has been focused on comparing the brain with computers. A variety of obvious analogies exist: for example, individual neurons can be compared with a transistor (although a neuron's computing power is probably closer to a simple calculator than a transistor), and the specialized parts of the brain can be compared with graphics cards and other system components. However, such comparisons are fraught with difficulties. Perhaps the most fundamental difference between brains and computers is that today's computers operate by performing often sequential instructions from an input program, while no clear analogy of a program appears in human brains. The closest to the equivalent would be the idea of a logical process, but the nature and existence of such entities are subjects of philosophical debate. Given model of computation, the Turing machine, this may be a functional, not fundamental, distinction. However, Maass and Markram have recently argued that "in contrast to Turing machines, generic computations by neural circuits are not digital, and are not carried out on static inputs, but rather on functions of time" (the Turing machine computes computable functions). Ultimately, computers were not designed to be models of the brain, though constructs like neural networks attempt to abstract the behavior of the brain in a way that can be simulated computationally.

In addition to the technical differences, other key differences exist. The brain is massively parallel and interwoven, whereas programming of this kind is extremely difficult for computer software writers (most parallel systems run semi-independently, for example each working on a small separate 'chunk' of a problem). The human brain is also mediated by chemicals and analog processes, many of which are only understood at a basic level and others of which may not yet have been discovered, so that a full description is not yet available in science. Finally, and perhaps most significantly, the human brain appears hard-wired with certain abilities, such as the ability to learn language (cf. Broca's area), to interact with experience and unchosen emotions, and usually develops within a culture. This is different from a computer in that a computer needs software to perform many of its functions beyond its basic computational capabilities.

The human brain is able to interpret and solve complex problems that are not formalized using its powers of pattern recognition and interpretation (strong AI), whereas the computer with current software and current hardware is only able to solve formalized problems (weak AI) due to more limited pattern recognition capability. A human can understand context in an arbitrary text, something even the most powerful and best software is not able to discern (as of 2008). A simple example is to attempt write a program that can determine if an arbitrary text contains humor or not.

There have been numerous attempts to quantify differences in capability between the human brain and computers. According to Hans Moravec, by extrapolating from known capabilities of the retina to process image inputs, a brain has a processing capacity of 0.1 quadrillion instructions per second (100 million MIPS). In comparison, the fastest supercomputer in the world, called Roadrunner and devised and built by engineers and scientists at I.B.M. and Los Alamos National Laboratory, is capable of handling 1.026 quadrillion calculations per second, and an average 4-function calculator is capable of handling 10 instructions per second. It is possible the brain may be surpassed by normal personal computers (in terms of Instructions Per Second, at least) by 2030.

The computational power of the human brain is difficult to ascertain, as the human brain is not easily paralleled to the binary number processing of today's computers. For instance, multiplying two large numbers can be accomplished in a fraction of a second with a typical calculator or desktop computer, while the average human may require a pen-and-paper approach to keep track of each stage of the calculation over a period of five or more seconds. Yet, while the human brain is calculating a math problem in an attentive state, it is subconsciously processing data from millions of nerve cells that handle the visual input of the paper and surrounding area, the aural input from both ears, and the sensory input of millions of cells throughout the body. The brain is regulating the heartbeat, monitoring oxygen levels, hunger and thirst requirements, breathing patterns and hundreds of other essential factors throughout the body. It is simultaneously comparing data from the eyes and the sensory cells in the arms and hands to keep track of the position of the pen and paper as the calculation is being performed. It quickly traverses a vast, interconnected network of cells for relevant information on how to solve the problem it is presented, what symbols to write and what their functions are, as it graphs their shape and communicates to the hand how to make accurate and controlled strokes to draw recognizable shapes and numbers onto a page.

See Also
* Brain
* Human brain

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