For a wrong word, underline the wrong word and write
the correct one in the blank provided at the end of the line.
For a missing word, mark the position of the missing word with
a"∧"sign and write the word you believe to be missing in the blank provided at
the end of the line. For an unnecessary word, cross the
unnecessary word with a slash and put the word in the blank provided at
the end of the line.
Is our conception of human neuron functioning and our
estimates of the number of neurons and connections in the human brain consistent
of what we know about the brain’s capabilities Perhaps human
neurons are far less capable than we think they are. If so, building a machine
with human level capabilities might bring longer than expected.
We find that estimates of the number of concepts-"chunks" of
knowledge-that a human expert in a particular field has mastered is remarkably
consistent: about 50,000 to 100,000. This approximate range appears to be valid
over wide range of human endeavors: the number of board positions mastered by a
chess grand master, the concepts mastered by an expert in a technical field,
such like a physician, the vocabulary of a writer. This type of
professional knowledge is, of course, only a small subset of the knowledge we
need to functioning as human beings. Basic knowledge of the world, including
so-called common sense, is more extensive. We also have an ability to recognize
patterns: spoken language, written language, objects, faces. And we have our
skills: walking, talking, catching balls. I believe that a reasonable
conservative estimate of the general knowledge of a typical human is a thousand
times greater than the knowledge of an expert in her professional field. This
provides us a rough estimate of 200 million chunks-bits of understanding,
concepts, patterns, specific skills-per human. As we will see below, if this
estimate is low (by a factor of up to a thousand), the brain is still big
enough. The number of neurons in the human brain is estimated at
approximately 100 billion, with an average of 1,000 connections per neuron, for
a total of 100 trillion connections. With 100 trillion connections and 100
million chunks of knowledge (including patterns and skills), we get an estimate
of about a million connections per chunk. Our computer simulations of neural
nets use a variety of different type of neuron models, all of which are
relatively simple. Efforts to provide detailed electronic models of real
mammalian neurons appear to show that while animal neurons are more complicated
than typical computer models, the difference in complexity is modest.