Psychology itself did not much develop before the twentieth century. A few thinkers like Aristotle had good ideas about psychology, but progress thereafter was slow; it seems to me that Aristotle's suggestions in the Rhetoric were about as good as those of other thinkers until around 1870. Then came the era of Galton, Wundt, William James and Freud - and we saw the first steps toward ideas about how minds work. But still, in my view, there was little more progress until the Cybernetics of the '40s, the Artificial Intelligence of the '50s and '60s, and the Cognitive Psychology that started to grow in the '70s and 80s.

Why did psychology lag so far behind so many other sciences? In the late 1930s a botanist named Jean Piaget in Switzerland started to observe the behavior of his children. In the next ten years of watching these kids grow up he wrote down hundreds of little theories about the processes going on in their brains, and wrote about 20 books, all based on observing three children carefully. Although some researchers still nitpick about his conclusions, the general structure seems to have held up, and many of the developments he described seem to happen at about the same rate and the same ages in all the cultures that have been studied. The question isn't, "Was Piaget right or wrong?" but "Why wasn't there someone like Piaget 2000 years ago?" What was it about all previous cultures that no one thought to observe children and try to figure out how they worked? It certainly was not from lack of technology: Piaget didn't need cyclotrons, but only glasses of water and pieces of candy.

Perhaps psychology lagged behind because it tried to imitate the more successful sciences. For example, in the early 20th century there were many attempts to make mathematical theories about psychological subjects - notable learning and pattern recognition. But there's a problem with mathematics. It works well for Physics, I think because fundamental physics has very few laws - and the kinds of mathematics that developed in the years before computers were good at describing systems based on just a few - say, 4, 5, or 6 laws - but doesn't work well for systems based on the order of a dozen laws. The physicist like Newton and Maxwell discovered ways to account for large classes of phenomena based on three or four laws; however, with 20 assumptions, mathematical reasoning becomes impractical. The beautiful subject called Theory of Groups begins with only five assumptions - yet this leads to systems so complex that people have spent their lifetimes on them. Similarly, you can write a computer program with just a few lines of code that no one can thoroughly understand; however, at least we can run the computer to see how it behaves - and sometimes see enough then to make a good theory.

However, there's more to computer science than that. Many people think of computer science as the science of what computers do, but I think of it quite differently: Computer Science is a new way collection of ways to describe and think about complicated systems. It comes with a huge library of new, useful concepts about how mental processes might work. For example, most of the ancient theories of memory envisioned knowledge like facts in a box. Later theories began to distinguish ideas about short and long-term memories, and conjectured that skills are stored in other ways.