roger_schank's picture
CEO, Socratic Arts Inc.; John Evans Professor Emeritus of Computer Science, Psychology and Education, Northwestern University; Author, Make School Meaningful-And Fun!
Case-Based Reasoning

We do case-based reasoning all the time, without thinking that that is what we are doing. Case-based reasoning is essential to personal growth and learning. While we hear people proclaim that mathematics teaches one to think, or knowing logic will help one reason more carefully, humans do a different kind of reasoning quite naturally.

When we go to a restaurant, we think about what we ordered the last time we were there and whether we want to order the same thing again. When we go out on a date, we think about how that person reminds us of someone we went out with before, and we think about how that turned out. When we read a book we are reminded of other books with similar themes or similar situations and we tend to predict outcomes on that basis. When we hear someone tell us a story about their own lives, we are immediately reminded of something similar that has happened to us.

Reminding, based on the examination of a internal library of cases, is what enables learning and is the basis of intelligence. In order to get reminded of relevant prior cases, we create those cases subconsciously by thinking about them and telling someone about them. Then, again subconsciously, we label the previously experienced cases in some way. The classic example of this is the steak and the haircut, a story about a colleague of mine who responded to my complaint about the fact that my wife couldn’t cook steak as rare as I wanted it by saying that twenty years earlier, in London, he couldn’t get his hair cut as short as he wanted it. While this may sound like a brain-damaged response, these two stories are identical at the right level of abstraction. They are both about asking someone to do something who, while being capable of doing it, has refused to do it, because they thought the request was too extreme. My friend had been wondering about his haircut experience for twenty years, My story reminded him of his own experience and helped him to explain to himself what had happened.

We are all case-based reasoners, but no one ever teaches us how to do this (except possibly in medical school, business school, and in law school.) No one teaches you how to label cases or how to retrieve cases from your own memory. Yet our entire ability to reason depends upon this capability. We need to see something as an instance of something we have seen before in order to make a judgment about it and in order to learn from it.

We do case-based reasoning naturally, and without conscious thought, so we tend to ignore its importance in thinking and learning. Whenever you participate in a conversation with someone about a subject of mutual interest you are having a kind of case-based reasoning party: exchanging stories and constantly being reminded of new stories to tell. Both participants come out slightly changed from the experience. That experience itself is, of course, a new case to be remembered and to be reasoned from in the future.