joyed most the math and physics and chemistry. So why electrical engineering, as opposed to going into physics? Around my family, no one had ever heard of a thing called a physicist. In this middle-class to lower-middle-class culture people were focused on getting a job that would make money, and engineers could get jobs and make money.

I happened to see an advertisement for scholarships being offered by an engineering school in Pittsburgh called Carnegie Institute of Technology. I got a scholarship, so that’s what I did. Life is an interesting set of choices, and the decision to go to Carnegie Tech (now Carnegie-Mellon University) was a fantastically good decision.

Something else there got you excited.

I had a nagging feeling that there was something missing in my courses. There’s got to be more to a university education! In the catalog I found a really interesting listing called “Ideas and Social Change,” taught by a young new instructor, James March. The first thing he did was to expose us to Von Neumann’s and Morgenstern’s “ Theory of Games and Economic Behavior.” Wow! This is mind-blowing! My first published paper was with March in social psychology, on decision-making in small groups.

March introduced me to a more senior and famous professor, Herbert Simon. That led to my taking a course from Simon called “Mathematical Models in the Social Sciences.” I got to know Herb, and got to realize that this was a totally extraordinary person.

In January 1956 Herb walked into our seminar of six people and said these famous words: “Over Christmas Allen Newell and I invented a thinking machine.” Well, that just blew our minds. He and Newell had formulated the Logic Theorist on December 15th, 1955. They put together a paper program that got implemented in the language called IPL- 1, which was not a language that ran on any computer. It was the first list processing language, but it ran in their heads.

That led to your first
exposure to computers.
When we asked Herb in that class,
“What do you mean by a machine?”
he handed us an IBM 701 manual, an
early IBM vacuum tube computer. That
was a born-again experience! Taking
that manual home, reading it all night
long—by the dawn, I was hooked on
computers. I knew what I was going
to do: stay with Simon and do more of
this. But Carnegie Tech did not have
any computers at that time, so I got a
job at IBM for the summer of 1956 in
New York.

What did you learn at IBM?

First, plug board programming, which was a phenomenally interesting thing for a geeky kid. Second, the IBM 650, because by that time it became known that Carnegie Tech would be getting a 650. Third, the IBM 704, which was a successor machine to the 701.

When I got back to Carnegie Tech in September 1956 and began my graduate work, there was Alan Perlis, a wonderful computer genius, and later the first Turing Award winner. Perlis was finishing up an amazing program called a compiler. That was “IT,” Internal Translator, and it occupied 1,998 words of the 2,000-word IBM 650 drum.

I had known about the idea of algebraic languages because in the summer at IBM someone had come down from the fourth floor to talk to the graduate students and tell them about a new thing that had just hit the scene. You didn’t have to write “CLA” for “clear and add,” and you didn’t have to write “005” for “add.” You could write a formula, and a program would translate that formula into machine language. FOR-TRAN. The guy was John Backus,

this idea has been
very important
for my career—
the experimental
approach to
computer science
as opposed to the
theoretical approach.

who had come downstairs to talk to us. IT’s introduction actually preceded Fortran’s by about nine months.

What was it like to use
a computer then?

There was no staff between you and the computer. You could book time on the computer, then you went and did your thing. A personal computer! I loved it. I loved the lights, I loved pressing the switches. This idea has been very important for my career—the hands on, experimental approach to computer science as opposed to the theoretical approach. Experiment turns out to be absolutely vital.

I was able to write a rather complicated—for that time—simulation of two companies engaged in a duopolis-tic decision-making duel about pricing of tin cans in the can industry, the second such simulation of economic behavior ever written. It led to my first conference paper, in December 1958, at the American Economics Association annual meeting.

 

What did you do for your dissertation? A model called EPAM, Elementary Perceiver and Memorizer, a computer simulation model of human learning and memory of nonsense syllables.

I invented a data structure called a Discrimination Net—a memory structure that started out as nothing when the learner starts. List structures had just been invented, but no one had tried to grow trees. I had to, because I would start with two nonsense syllables in the Net, and then the next pair would come in and they’d have to “grow into” the net somewhere. These were the first adaptively growing trees. Now here’s an amazing and kind of stupid thing that shows what it means to focus your attention on x rather than y. We were focused on psychology. We were not focused on what is now called computer science. So we never published anything about those adaptively growing trees, except as they related to the psychological model. But other people did see trees as a thing to write papers about in the IT literature. So I missed that one!

 

Where was your first academic job? I had wanted to come to the West Coast, and the University of California