History Of Memory
From the time when man first began to depend on his mind for coping with his environment, the possession of an excellent memory has been a step to positions of command and respect.
The History Of Memory
It is difficult to say exactly when and where the first integrated ideas on memory arose. The first sophisticated concepts, however, can be attributed to the Greeks, some 600 years before the birth of Christ. As we look back on them now, these 'sophisticated' ideas were surprisingly naive, especially since some of the men proposing them are numbered among the greatest thinkers the world has ever known.
In the sixth century BC, Parmenides thought of memory as being a mixture of light and dark or heat and cold. He believed that as long as any given mixture remained unstirred, the memory would be perfect. As soon as the mixture was altered, forgetting occurred. Diogenes of Apollonia advanced a different theory, in the fifth century BC. He suggested that memory was a process that consisted of events producing an equal distribution of air in the body. Like Parmenides, he thought that when this equilibrium was disturbed, forgetting would occur.
Not surprisingly, the first person to introduce a really major idea in the field of memory was Plato, in the fourth century BC. His theory is known as the Wax Tablet Hypothesis and is still accepted by some people today, although there is growing disagreement. To Plato, the mind accepted impressions in the same way that wax becomes marked when a pointed object is applied to its surface. Plato assumed that once the impression had been made it remained until it wore away with time, leaving a smooth surface once again. This smooth surface was, of course, what Plato considered to be equivalent to complete forgetting - the opposite aspect of the same process. As will become clear later, many people now feel that memory and forgetting are two quite different processes. Shortly after Plato, Zeno the Stoic slightly modified Plato's ideas, suggesting that sensations actually 'wrote' impressions on the wax tablet. Like the Greeks before him, when Zeno referred to the mind and its memory, he did not place it in any particular organ or section of the body. To him as to the Greeks, 'mind' was a very unclear concept.
The first man to introduce a more scientific terminology was Aristotle, in the late fourth century BC. He maintained that the language previously used was not adequate to explain the physical aspects of memory. In applying his new language Aristotle attributed to the heart most of the functions that we now attribute to the brain. Part of the heart's function, he realised, was concerned with the blood, and he felt that memory was based on the blood's movements. He thought that forgetting was the result of a gradual slowing down of these movements. Aristotle made another important contribution to the subject of memory when he introduced his laws of association of ideas. The concept of association of ideas and images is now known to be of major importance to memory. Throughout this book this concept will be discussed and applied.
In the third century BC, Herophilus introduced 'vital' and 'animal' spirits to the discussion. He thought that the vital, or 'higher order', spirits produced the 'lower order' animal spirits, which included the memory, the brain and the nervous system. All of these he thought to be secondary in importance to the heart. It is interesting to note that one reason advanced by Herophilus for man's superiority over animals was the large number of creases in his brain. (These creases are now known as the convolutions of the cortex.) Herophilus, however, offered no reason for his conclusion. It was not until the nineteenth century, more than 2000 years later, that the real importance of the cortex was discovered.
The Greeks, then, were the first to seek a physical as opposed to a spiritual basis for memory; they developed scientific concepts and a language structure that helped the development of these concepts; and they contributed the Wax Tablet Hypothesis, which suggested that memory and forgetting were opposite aspects of the same process.
The theoretical contributions by the Romans to our knowledge of memory were surprisingly minimal. The major thinkers of their time, including Cicero in the first century BC and Quintilian in the first century AD, accepted without question the Wax Tablet Hypothesis of memory and did little further work on the subject. Their major and extremely important contributions were in the development of memory systems. They were the first to introduce the idea of a Link System and a Room System, both of which will be described in this course.
The Influence Of Christian Church
The next major contributor to memory theory was the great physician Galen in the second century AD. He located and delineated various anatomical and physiological structures and made further investigations into the function and structure of the nervous system. Like the later Greeks, he assumed that memory and mental processes were part of the lower order of animal spirits. He thought that these spirits were manufactured in the sides of the brain and that, consequently, memory was seated there. Galen thought that air was sucked into the brain and mixed with the vital spirits. This mixture produced animal spirits that were pushed down through the nervous system, enabling humans to experience sensation.
Galen's ideas on memory were rapidly accepted and condoned by the church, which at this time was beginning to exert a great influence. His ideas became doctrine, and as a result little progress was made in the field for 1500 years. These intellectual strictures stifled some of the greatest minds that philosophy and science have produced. In the fourth century AD St Augustine accepted the church's idea that memory was a function of the soul and that the soul was located in the brain. He never expanded on the anatomical aspects of these ideas.
From the time of St Augustine until the seventeenth century there were almost no significant developments, and even in the seventeenth century new ideas were restricted by doctrine. Even so great a thinker as Descartes accepted Galen's basic ideas, although he thought that animal spirits were sent from the pineal gland on special courses through the brain until they came to the part where memory could be triggered. The more clear-cut these courses, the more readily, he thought, would they open when animal spirits travelled through them. It was in this way that he explained the improvement of memory and the development of what are known as memory traces. A memory trace is a physical change in the nervous system that was not present before learning. The trace enables us to recall.Another great philosopher, who went along with the tide, was Thomas Hobbes, who discussed and considered the idea of memory but contributed little to what had already been said. He agreed with Aristotle's ideas, rejecting nonphysical explanations of memory. He did not, however, specify the real nature of memory, nor did he make any significant attempts to locate it accurately.
It is evident from the theories of the seventeenth-century intellectuals that the inhibiting influence of Galen and the church had been profound. Practically all these great thinkers accepted without question primitive ideas on memory.
Transitional Period - The Eighteenth Century
One of the first thinkers to be influenced by the Renaissance and by the ideas of Newton was David Hartley, who developed the vibratory theory of memory. Applying Newton's ideas on vibrating particles, Hartley suggested that there were memory vibrations in the brain that began before birth. New sensations modified existing vibrations in degree, kind, place and direction. After being influenced by a new sensation, vibrations quickly returned to their natural state. But if the same sensation appeared again, the vibrations took a little longer to return. This progression would finally result in the vibrations remaining in their 'new' state, and a memory trace was thus established.
Other major thinkers of this period included Zanotti, who was the first to link electrical forces with brain functions, and Bonnet, who developed the ideas of Hartley in relation to the flexibility of nerve fibres. He felt that the more often nerves were used, the more easily they vibrated, and the better memory would be. The theories of these men were more sophisticated than previous ones because they had been largely influenced by developments in related scientific fields. This interaction of ideas laid the groundwork for some of the modern theories of memory.
The Nineteen Century
The Nineteenth Century With the development of science in Germany in the nineteenth century, some important advances occurred. Many of the ideas initiated by the Greeks were overthrown, and work on memory expanded to include the biological sciences.
Georg Prochaska, a Czech physiologist, finally and irrevocably rejected the age-old idea of animal spirits on the grounds that it had no scientific basis and that there was no evidence to support it. He felt that limited existing knowledge made speculation on the location of memory in the brain a waste of time. 'Spatial localization may be possible,' he said, 'but we just do not know enough at the moment to make it a useful idea.' It was not for some fifty years that localizing the area of memory function became a useful pursuit.
Another major theory presented in this century was that of Pierre Flourens, a French physiologist, who 'located' the memory in every part of the brain. He said that the brain acted as a whole and could not be considered as the interaction of elementary parts.