In this chapter, the authors discuss how human memory really works, and why this is important for teachers to know. They describe how control participants would perform on this cognitive task. William James wrote a book in 1890 – Principles of Psychology – which, unlike cognitive psychology, was based entirely on his own intuitions – or, more formally, introspections – rather than experiments and data. When cognitive psychologists talk about short-term memory, they are really just talking about a very brief period of time. The first patient to demonstrate a profound loss of long-term memory along with perfectly intact short-term memory was called H. M. To illustrate how sensitive H. M's memory is to this distinction between short- and long-term memories, consider the following experiment. The kind of memory that the authors usually think of when they talk about memory in everyday life is declarative memory.