My father grew up during the Great Depression. When he was in the sixth grade, his father died of cancer, and my dad dropped out of school so that he could go to work and help support his mother and siblings. Despite having only an elementary school education, my father was fortunate enough to soon be able to go to work for the Western of Alabama Railroad, at the age of 15 as a carmen's apprentice. He worked a good union job for that railroad for the next 45 years, first as a railroad coach carpenter and then as a diesel engine mechanic. My father had a lifelong yearning for the education that had been denied him owing to his circumstances. From a very young age I remember him telling me to "get an education, that's the way out." He instilled in me a concrete understanding that learning is an opportunity, and that in a very tangible way that knowledge is power.
Shortly before I received my Ph.D. from Vanderbilt University, I had a realization. I realized that, like my father before me, I was likely to spend the rest of my life working on a single thing, so whatever that thing was, it had better be interesting to me. I asked myself the question: "What is the most interesting thing in the world?" For me, the answer to that question was to understand learning and memory. In retrospect, this answer might not be surprising given my father's lifelong emphasis on the importance of learning as an opportunity to be vigorously pursued. From that point on, I have undertaken a course of laboratory investigation aimed at trying to understand learning and memory.
Knowledge really is power, and learning is the tool we use to get it. For that reason, humans have evolved extremely sophisticated mechanisms for learning new information and storing it for subsequent recall. This book will describe recent laboratory findings that have begun to scratch the surface of the amazingly complex phenomenon of learning and memory, focusing on their cellular and molecular bases.
An understanding of the cellular and molecular basis of learning and memory of course requires a firm foundation of understanding the behavioral processes these mechanisms subserve. This first chapter serves as an introduction to the basics of learning and memory, its theory and terminology. It will provide you with the fundamental terms most psychologists use to describe the types and forms of learning and memory that we will be discussing throughout the book.
What is learning? Before we can begin to discuss categorizing types of learning and memory effectively, it is useful to define both of the terms we will be using extensively throughout this book: learning and memory. Both of these terms are so widely used and implicitly understood that there is a great temptation to say "learning is when you learn something and memory is when you remember it." This type of definition obviously is not going to take us very far.
Upon serious reflection, we can clearly see that neither learning nor memory will be easy to define, and indeed learning and memory psychologists continue to debate these definitions to this day. Thus, I am delivering the caveat that the definitions I
have chosen to use, even though they are derived from the literature, are not universally accepted. I define learning as the acquisition of an altered behavioral response due to an environmental stimulus. In other words, learning is when an animal changes its behavior pattern in response to an experience. Note that what is defined is a change in a behavior from a preexisting baseline. I am not defining learning as a response to an environmental stimulus, but rather as an alteration in that response due to an environmental stimulus. An animal has a baseline response, experiences an environmental signal, and then has an altered response different from its previous response. This I define as learning (see Figure 1).
Memory is defined as the storage of the learned item, which of course must be subject to recall by some mechanism.
I like these definitions because at heart I am an experimentalist, and these are clear functional definitions that lend themselves to experimental application. An experimentalist must be able to observe something (and ideally measure it) in order to be able to test a hypothesis. The definitions of learning and memory that I use derive directly from the experimentalist mindset. This practical orientation is at once both a strength and a weakness for the definitions—their ready application in practice leads to limitations for their use in theory.
Learning: The acquisition of an altered behavioral response due to an environmental stimulus.
Memory: The processes through which learned information is stored.
Recall: The conscious or unconscious retrieval process through which this altered behavior is manifest.
FIGURE 1 Definitions of learning, memory, and recall.
For example, one criticism of the definition of learning that I (and many others) use is that it is too narrow. If someone learns my name and stores it as a perfectly legitimate memory, that learned item may never be manifest as an altered behavioral output on their part. This is a completely valid theoretical criticism and a limitation to the definition. My only rebuttal is that in order for you to ever prove to me that such a memory exists, you would need to demonstrate an altered behavioral output on the part of the person involved. For example, they would need to respond with "David" instead of "I don't know" when you showed them my picture. This is really more of a practical Catch-22
than a logical rebuttal, however, and it is certainly clear that the definition does not adequately cover every type of memory. I will leave for other authors the discussion of whether memories are in fact quantum Schroedinger's Cats that don't exist until recalled (a discussion some would take quite seriously).
At the other end of the spectrum is the criticism that the definition is too broad. It certainly covers many types of alterations in behavior such as simple sensitization and habituation, which most people would not consider to be "real" learning (this is illustrated in Box 1). Nevertheless, a considerable body of literature is available indicating, and most researchers in the
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