In today’s world, is there a reason to memorize anything? You can find any factual information you need in seconds via the Internet. Perhaps instead of learning facts, some teachers believe it’s better to practice critical thinking, to have students work at evaluating all the information available on the Internet rather than trying to commit some small part of it to memory.
Data from the last thirty years lead to a conclusion that is not scientifically challengeable: thinking well requires knowing facts, and that’s true not simply because you need something to think about. The very processes that teachers care about most-critical thinking processes such as reasoning and problem solving-are intimately intertwined with factual knowledge that is stored in long-term memory (not just found in the environment). 
Much of the time when we see someone apparently engaged in thinking, he or she is actually engaged in memory retrieval. As I described yesterday, memory is the cognitive process of first resort. When faced with a problem, you will first search for a solution in memory, and if you find one you will very likely use it. For example, you might have a friend who can walk into someone else’s kitchen and produce a nice dinner from whatever food is around. When your friend looks in a cupboard, she doesn’t see ingredients, she see recipes. She’s drawing on her extensive background knowledge about food and cooking. Take her to the garage instead, give her a box of auto parts and she will not be able to rebuild your carburetor.
It’s often difficult for students to understand new ideas, especially ones that are really novel, meaning they aren’t related to other things they have already learned. That’s because people understand new ideas (things we don’t know) by relating them to old ideas (things we do know).
Teachers put this idea to work all the time when they use analogies, which help us understand something new by relating it to something we already know about. Science textbooks, for example, usually compare electricity to the movement of water. Electrons moving along a wire are like water moving through a pipe.
So, understanding new ideas is mostly a matter of getting the right old ideas into working memory and then rearranging them-making comparisons we hadn’t made before, or thinking about a feature we had previously ignored.
This is why understanding is remembering in disguise. No one can pour new ideas into a student’s head directly. Every new idea must build on ideas that the student already knows. To get a student to understand, a teacher (or a parent or book or television program) must ensure that the right ideas from the student’s long-term memory are pulled up and put into working memory.
Even this is easy to say but hard to accomplish. Give a student an explanation and a set of examples, and they probably still don’t understand right away. Even when students “understand,” there are really degrees of comprehension. One student’s understanding can be shallow while another’s is deep. Second, even if students understand in the classroom, this knowledge may not transfer well to the world outside the classroom. That is, when students see a new version of what is at heart an old problem, they may think they are stumped, even though they recently solved the same problem. They don’t know that they know the answer! I elaborate in detail on these two issues – shallow knowledge and lack of transfer – in my book.
Tomorrow: In defense of practice
Daniel T. Willingham is a professor of psychology at the University of Virginia and the author of Why Students Don’t Like School: A Cognitive Scientist Answers Questions About How the Mind Works and What it Means for the Classroom (Jossey-Bass, 2009) from which this post was adapted.
