Life-Span Maintenance of Knowledge

Harry P. Bahrick, Lynda K. Hall, Melinda K. Baker

• Publisher: Psychology Press
• Year: 2013
• Print ISBN: 9781848726505
• eBook ISBN: 9781136496141
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

This volume describes how well we maintain the knowledge we acquire throughout life. Research traditionally focuses on memory for events that are retained over short time periods that can be accommodated in experiments. This book, by contrast, uniquely describes the evolution of methods suitable for investigating memory of complex knowledge acquired over several years and retained during the entire life-span. The methods substitute statistical for experimental controls, and the investigations involve several hundred participants whose memory is tested up to 50 years after they acquired the knowledge in question.

The book covers educational content, such as mathematics and foreign languages; knowledge acquired incidentally, such as the streets and buildings of the cities in which we live; and knowledge acquired through the media. Previously unpublished research on age-related access to knowledge is included.

The analyses are based on the accessibility/availability ratio, a metric presented for the first time. This metric allows comparisons of the portion of available knowledge that can be recalled as a function of age, education and other individual differences, and as a function of the domain of knowledge in question. The ratio can be used to evaluate methods of instruction and methods of studying. It can also be used to evaluate memory development and to diagnose memory pathology.

The volume will be of interest to researchers in human memory, developmental psychologists, gerontologists in academic and applied settings, and educators.

An Historical Perspective

This book describes research on how knowledge is maintained during the human life-span. For the past 130 years, the vast majority of memory research has focused on short retention periods of seconds, minutes or hours. The reasons for this emphasis lie in the history and the sociology of our science. We begin our narrative with an introduction that explains the origins and consequences of this long tradition.

☐ Experimental Psychology

Memory research began when Herman Ebbinghaus, a German professor, learned and later relearned lists of meaningless syllables. By systematically varying the interval between learning and relearning the lists, he was able to show that forgetting of the lists followed a predictable negatively accelerated course over time. His method paralleled the experimental method used by physics, the most prestigious science of the nineteenth century. Along with the work of other pioneers, Ebbinghaus' investigations convinced the German professoriate that scientific methods could be utilized to explore a number of questions about human nature that had previously been examined only by philosophers. Based on such evidence, psychology became established in Germany as a scientific discipline independent of philosophy.¹

Ebbinghaus was the only participant in his experiments, and he memorized content that had no specific meaning. Both of these decisions were deliberate and important. When physicists repeat experiments, the outcome may show minor variations. These variations are generally attributed to experimental error and are therefore regarded as trivial. By analogy, Ebbinghaus reasoned that a single subject should suffice to demonstrate the generic properties of the human memory system. Variations in the outcome of repetitions of an experiment with other subjects would be of little import if his results reflected generic aspects of brain functions. Ebbinghaus knew, of course, that people differ in regard to how quickly they learn and forget many things, but by choosing meaningless content, he expected to diminish such differences. He was correct in this regard; his basic conclusions regarding the course of memory for meaningless material have stood the test of time.

The Ebbinghaus experimental procedures established standards for memory research that were followed for many years. At about the same time, other scientists who were trained as physicists and/or physiologists pioneered experimental methods that documented generic characteristics of sensory experiences, reaction time and learning. Based on earlier work by Weber (1834), Fechner (1912) developed the methods of psychophysics. His experimental procedures showed that the ability to detect changes in the intensity of sensory stimuli depends upon relative, not absolute, amounts of stimulus change. For example, we can detect the difference between weights of 10 grams and 11 grams, but not the difference between 100 grams and 101 grams. A weight of 110 grams would be required for the latter difference to be equally detectable. Individual differences again had minor impact in this domain, and Fechner's general conclusions were valid over a wide range of stimulus intensities, not only for the tactual sensitivity, but also for vision, hearing and other sense modalities.

Helmholtz, the most distinguished physiologist and physicist of his time, was able to measure the speed of nerve conduction by stimulating the nerve of a frog at various distances from the attached leg muscle. When he stimulated the nerve at longer distances from the muscle, more time elapsed before the muscle contracted. He attributed the time differential to the increased distance the impulse travelled along the nerve. Based on these data, he was able to calculate the speed of nerve conduction. Although the speed did not differ greatly for the nerves of frogs and humans, the time required by humans to react voluntarily to a simple stimulus was much longer than could be accounted for by the speed of nerve conduction. Follow-up experiments on human reaction time showed that most of the additional time required to react involved central processes in the brain, and a series of subsequent experiments explored the timing associated with a variety of mental processes. The emphasis in this early work on reaction time was again on identifying common human characteristics as opposed to sources of individual differences.

Philosophers had long theorized about how we acquire knowledge. British empiricist philosophers (Locke, 1975; Mill, 1875) concluded that knowledge consists of associations and those associations are formed when sensory experiences repeatedly occur either simultaneously or in close temporal succession. These philosophers saw associations as the basic units of knowledge and the formation of associations as the fundamental process of learning. Pavlov, a physiologist, was well aware of the key role philosophers had assigned to associations, and he realized the potential importance of finding a scientific method to study the acquisition of associations. His seminal experiments with dogs demonstrated how associations can be strengthened or weakened, and his conditioning procedures opened the legacy of associationist theories to scientific exploration.

Notably, the Ebbinghaus procedures, Fechner's psychophysical methods, the research on reaction time and Pavlovian conditioning all focused on generic findings, not on individual differences. In the tradition of the established sciences, these pioneer investigators regarded individual differences as relatively unimportant. This focus on experimental methods and on generic findings became fundamental to the new discipline appropriately named experimental psychology.

☐ The Psychology of Individual Differences

A very different scientific approach to exploring human nature began in England at about the same time during the 19^th century, and it was based on Darwin's theory of evolution. Darwin was a naturalist who developed his theory by careful observations of nature as opposed to performing experiments. He was an independent investigator, not a professor in a university, and he was unencumbered by the traditions of academia. He had no direct interest in founding psychological science, but his work had an enormous influence on the development of psychological science.

During his long voyage, Darwin observed similarities and differences among species, and his goal was to explain how such differences came about. In contrast to the founders of experimental psychology, his theory of natural selection focused on individual differences among the members of each species, not on the generic characteristics common to all members of a species. His observations led him to conclude that certain characteristics of individuals were adaptive in the sense that they improved the chances of surviving in particular environments. Organisms that possessed adaptive characteristics were likely to live long enough to reproduce and to pass their adaptive characteristics to their offspring. By doing so, they increased the chances that their offspring would live long enough to reproduce. This process of natural selection was the primary basis for the evolution of new species.

It was Darwin's younger cousin, Sir Francis Galton, who focused on human individual differences in the context of Darwinian Theory. Galton's goal was to gain control of evolution. Based on Darwinian principles, he wanted to create a superior race of human beings (Galton, 1901). To accomplish that, he advocated what he called eugenic principles. These principles involved promoting progeny of individuals who possess adaptive characteristics, such as superior intelligence, and diminishing progeny of non-adaptive characteristics, such as inferior intelligence.

We must note that Galton's eugenic ideas inspired sinister consequences. In the United States, the eugenic movement influenced the enactment of ethnically and racially selective immigration policies intended to diminish the influx of allegedly genetically inferior individuals. Eugenicists also promoted legislation for involuntary sterilization of individuals designated as feebleminded. Several states, including California, sterilized a substantial number of individuals under that program. Eugenic ideology was part of Nazi Germany's plan to develop a superior Aryan race. To accomplish their goal, the Nazi regime committed genocide of millions, practiced mass sterilization and was responsible for the most devastating atrocities in recorded history.

Galton's ideas would certainly be considered racist and sexist by contemporary standards. He excluded women from his investigations, and he believed in the superiority of the Nordic race. It is not likely, however, that Galton could have anticipated the catastrophic consequences of eugenic ideology. In the history of psychology, he will be remembered mostly for his pioneering research on individual differences.

Galton began by measuring individual differences he expected to be adaptive. His early attempts included measuring the volume of brains and other anthropological characteristics. However, these measures turned out to be unrelated to the achievements of individuals. He then began to investigate human accomplishments directly, by focusing on what he called the inheritance of genius (Galton, 1880). He identified a large number of English men who were recognized for their outstanding accomplishments (including members of his own family), and he developed a primitive rating scale to evaluate the magnitude of their contributions. He also evaluated the accomplishments of their male offspring. He found that men of outstanding accomplishment produced sons who tended to achieve far more than the average English male, but generally less than their outstanding fathers. Based on these data, he devised a simple mathematical index of regression to the mean that led successive incumbents of the Galton chair of eugenics at London University College (Pearson, Spearman) to develop contemporary correlational statistics.

Darwin's theory, as well as Galton's focus on individual differences in human achievement, had a great impact on the world and on American culture in particular. Organized religion generally rejected evolutionary theory because it was seen as conflicting with the Biblical account of creation. That opposition remains formidable in the United States 150 years after the theory was first advanced. At the same time, core aspects of evolutionary theory appealed strongly to American culture. The United States had an historic tradition of idolizing strong, self-made men and sometimes women. This tradition dates back to the heroic pioneers who survived under challenging conditions and succeeded in conquering the wilderness. The evolutionary emphasis on competition and on survival of the fittest was congruent with that view of American history.

Evolutionary theory also inspired the American philosophy of pragmatism, a movement that examined the adaptive values of social institutions. Pragmatists had a pervasive influence on education in the United States. They promoted the change from a classical curriculum to one with a more adaptive focus, designed to prepare students for their adult roles as citizens, parents, workers and consumers. Functional psychologists collaborated closely with pragmatists. Thorndike's (1906) programmatic research on learning provided the empirical basis for profound changes in American schools. The emphasis in pedagogy shifted from discipline and punishment to reward as a way of motivating students. The traditional, passive role of students in the classroom changed to having students actively involved, interacting with teachers and with each other, and the classic curriculum in which “one size fits all” was replaced with curricular options responsive to the varying interests and abilities of students.

As a 14-year-old immigrant from Austria, I experienced the transition from a Viennese gymnasium to an American high school. The contrast between pedagogy based on discipline and fear, to the friendly, supportive atmosphere of an American school was dramatic and liberating, and it motivated me to become an academic. Ultimately, American principles of education and child rearing profoundly influenced most of the western world.

The most direct influence of Galton's work on psychological science was the impetus it provided for measuring individual differences (Hothersall, 2004). Psychologists became experts in measurement. Cattell (1890), Binet (1903) and their successors developed tests of intelligence, aptitudes, abilities, personality and interests. Testing became an integral part of education, of psychological diagnosis, of counseling and guidance, and of selecting workers in industry. Constructing and administering tests led to the development of specialized psychological professions. These included school and educational psychology, developmental psychology, clinical psychology, counseling psychology, sport psychology, military psychology and industrial psychology. Beyond giving rise to specialized applied professions, the study of individual differences led to the development of psychological theories and methods in each of the above psychological domains. Examples are theories of personality, of creativity, of abnormalities, of therapy, of intelligence, of development and of cognitive aging.

☐ The failure to Integrate Experimental Psychology and the Psychology of Individual Differences

Memory research remained focused on generic principles for over 100 years. To be sure, Ebbinghaus' successors involved more than single participants in their experiments, and the saving scores he used as an indicant of memory were replaced by more reliable indicants of recall and recognition (Bahrick, 1967). However, the prevailing experimental paradigm relegates individual differences in the outcome of experiments to the error terms of hypotheses testing statistics. Within the experimental paradigm, individual differences serve only as noise, complicating our ability to identify statistically significant effects. Memory experiments are designed to test hypothesis regarding the effects of treatments on the average performance of groups; they generally do not examine differential effects on individuals within the groups. The neglect of individual difference variables and their interaction with treatment variables continues to limit most memory experiments. This limitation has been deplored by others (Bauer, 2011).

The experimental approach also limits memory research to effects that occur over short time intervals that can be monitored in experiments, and to the effects of variables that can be manipulated by an experimenter. These restrictions preclude investigating a wide range of memory phenomena that are of great societal interest. For example, the content, the durability and the accuracy of autobiographical memories are of interest to developmental psychologists, to clinical psychologists, to novelists, etc. Autobiographical memories are likely to be unique to the individual, and they are formed and often maintained over long periods. Autobiographical memories are often established under conditions that are difficult to duplicate experimentally, and neither long term maintenance nor accuracy of such memories can be investigated within the constraints imposed by experiments.

These limitations also reduce the utility of psychological science in applied domains. The durability of knowledge acquired in schools is a critical concern of teachers, students and of society. However, the time involved in acquiring and maintaining knowledge is far too long to lend itself to experimental research. Kintsch (1974, p. 4) stated the issue clearly over 35 years ago:

Most of the experimental research concerning memory has never really dealt with problems of the acquisition and retention of knowledge, but with episodic memory which is not at all the problem of interest in education … An educational technology squarely based upon psychological research needs research concerned with problems of knowledge.

For another example, the judicial system depends heavily on the validity of eyewitness testimony. The time elapsed between witnessing events and testifying about them is usually much longer than can be accommodated in experiments. Beyond these temporal limitations, experimental controls are not available when critical memories are formed, and it is difficult to simulate these conditions experimentally.

Control is the essence of the scientific method, and experiments generally afford the best opportunities of control. Therefore, scientists sensibly continue to view experiments as the method of choice. However, topics that are of great significance to society should not be ignored or neglected simply because the relevant phenomena cannot be accommodated under a prevailing paradigm (Bahrick, 2005).

☐ Scientific Progress as a function of Methodology and Sociology

Scientific advances depend on methodological innovation. New methods allow previously elusive phenomena to be investigated, and they often yield scientific breakthroughs. For a few examples, the invention of the telescope, the microscope, the technology of classical conditioning and neuroimaging methods each enabled important questions to be explored empirically.

Social influences on scientific progress are also significant, and these influences can be obvious or subtle. Political ideology and policy can prohibit and/or punish publication o...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• About the Authors
• Preface
• Chapter 1 An Historical Perspective
• Chapter 2 The Ohio Wesleyan Memory Research Program
• Chapter 3 Acquisition and Maintenance of Knowledge
• Chapter 4 Experimental and Quasi-Experimental Investigations of Overlearning
• Chapter 5 Fluctuations of Access to Marginal Knowledge
• Chapter 6 Initial Investigations of Age-Related Access to Knowledge
• Chapter 7 Larger Scale Investigations of Age-related Access to Naturalistically Acquired Knowledge
• Chapter 8 Distortions of Knowledge
• Chapter 9 Summing Up
• Appendix A Stabilization of Preventive and Corrective Interventions for Younger and Older Adults
• Appendix B The Effects of Cognitive Aging on Recalling Familiar Memory Content: The Role of Contextual Cues
• Appendix C Metacognitive Judgment and Age-Related Access to Marginal Content
• Appendix D The Accessibility/Availability Ratio: A Metric to Compare Access to Knowledge Across Age Groups and Content Domains
• Appendix E The Effect of Cognitive Aging on Access to Foreign Language Vocabulary
• Appendix F The Effect of Cognitive Aging on Access to Names of Prominent People
• References
• Author Index
• Subject Index