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THE WORLD OF BIOLOGICAL RESEARCH A small insight into the changing dynamics of the life sciences is pro- vided by observation of the fraction of the total population within each research area under 34 years of age. This fraction is remarkably close to 21 percent for virtually all research areas, with a few interesting exceptions. Only 11 percent of those engaged in the study of disease mechanisms are within this age group, presumably reflecting the long period of residency training for physicians. In contrast, 23 percent of those in developmental biology and 28 percent of those in molecular biology and biochemistry were under the age of 34 at the time ot this survey, ~na~caung anal In one recent past these two fields, as compared with the other research areas, have be- come increasingly attractive to young scientists. Only 18 percent of all those attracted into the life sciences from the physical sciences were within this age group, indicating that there has been no dramatic upsurge of interest in the life sciences among young chemists or physicists. The reverse situation is in accord with the same suggestions. For the entire population, 18 percent were 50 years of age or older, but only 12 percent of those in molecular biology and biochemistry fell within that age range, in contrast with 25-28 percent in the areas of disease mechanisms evolutionary and systematic biology, morphology, and nutrition. Of some interest are the attributes of the group of investigators origi- nally trained only as M.D.'s or in the other health professions. They are older, with only 15 percent under 34 years of age, but 42 percent within the age span 40-49. Logically, disease mechanisms constitute their prin- cipal single interest (27 percent of the total), but they are also represented in every other research area with the exception of systematic biology, major interests being physiology (22 percent), molecular biology and biochem- is*y (15 percent), cellular biology (9 percent), and pharmacology (8 per- cent) . The 456 women showed only a few distinct tendencies to differ from the distribution of the men. Women tended to avoid physiology, ecology, and systematic and behavioral biology, and 28 percent of all female re- spondents work in molecular biology and biochemistry. . . .. ~.. . _ ~ , , ~, ~ 1~ POSTDOCTORAL TRAINING Prior to World War II, postdoctoral research training experience was a privilege granted very few young scientists. Fellowships were scarce, and only the most highly talented could aspire to such opportunity. Since avail- able research grants were decidedly limited in size, few senior academic investigators commanded the means to support eligible new M.D.'s or Ph.D.'s desirous of embarking upon the apprentice training characteristic 239

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240 THE LIFE SCIENCES of the postdoctoral experience. That situation no longer obtains. Post- doctoral experience has become almost the norm rather than the exception, and we are entirely convinced that this is in the national interest. However, the situation has given rise to concern among those less closely associated with research in these disciplines. For example, agencies that provide support for postdoctoral training are uncertain of its value. Edu- cational institutions in which postdoctoral fellows abound are uncertain of their institutional responsibility for this enterprise. Institutions that, per- haps until 1969, have had difficulty in recruiting sufficient staff to meet teaching obligations largely the four-year colleges and junior colleges, but also a significant number of medical schools, as well as industry and some federal laboratories have complained that the postdoctoral system is a holdup in the pipeline that, in the steady state, keeps a substantial number of bright young investigators out of the regular job market. We appreciate these problems, but consider that the benefits of postdoctoral education far outweigh these transient difficulties. Let us consider here the postdoctoral training experience of our responding population of life scien- tists. In the following chapter there is a summary of the numbers and activities of postdoctoral fellows in training in 1967-1968, as well as an analysis of the contribution of postdoctoral education to the operation of the entire endeavor. Of the 12,151 investigators in the study, 5,041 had had at least one postdoctoral appointment, including 1,402 M.D.'s who had had postdoctoral experience in which research was their major responsibility. Three fourths of those who had had postdoctoral experience are now in academic life. Indeed, 45 percent of the 8,143 scientists now employed by universities had enjoyed postdoctoral experience, compared with 21 percent of the scientists in industry and 31 percent of those in the federal establishment. Taken across all disciplines, postdoctoral experience somewhat enhances the opportunity for employment in the federal government and markedly enhances the opportunity for employment in the universities. It is our impression that in universities with major commitments to graduate educa- tion and research, measured in supporting dollars and number of graduate students, faculty appointments for individuals who have not had postdoctoral experience are probably rare indeed. According to a National Academy of Sciences study of postdoctorals,* 74 percent of all new appointees to the rank of instructor or assistant professor in 21 departments of biological sciences in 10 "leading" institutions either came from other university faculties or had just held postdoctoral appointments. * The Invisible University: Postdoctoral Education in the United States, Report of a Study Conducted under the Auspices of the National Research Council, National Academy of Sciences, Washington, D.C., 1969.

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THE WORLD OF BIOLOGICAL RESEARCH However, the trend to postdoctoral education is not universal across all biological fields. For example, of the 855 individuals with graduate train- ing in agricultural fields, only 35 had had postdoctoral appointments. In contrast, postdoctoral training was commonplace among M.D.'s since it has become the conventional medium for obtaining research training among this group. As shown in Table 13, postdoctoral training was less frequent among botanists (29 percent) than among biochemists (53 percent), with the other disciplines ranging in between. Postdoctoral training was frequently taken in fields other than those in which scholars had their initial doctoral experience. Thus, of the zoologists and botanists who did take postdoctoral training, less than half did so in zoology and botany departments. Again, the biochemists appear as the other extreme. Not only did a larger fraction of biochemists than other life scientists take postdoctoral training, but a decidedly larger fraction remained within biochemistry for their postdoctoral experiences. Since an additional 540 individuals who had taken their original graduate education in fields other than biochemistry sought post- doctoral training in biochemistry, postdoctoral education is a major aspect of life in biochemistry departments. Large numbers of those trained in biochemistry in graduate school later work in other disciplinary areas, while many individuals enrich their original disciplinary education by a one- or two-year postdoctoral experience in biochemistry and then, when they become independent investigators, return to their original disciplines and research areas or enter yet other research areas. These data uphold one of the primary arguments in support of the trend toward postdoctoral experience as a normal component of the education of those who later will espouse careers in which research is a major activity, viz., that this constitutes a unique opportunity to broaden one's horizons, learn new techniques, and become familiar with the style of other sub- disciplines, while profiting by the examples of different master scientists. The overall situation is reflected in the totals of Table 13. Of 5,765 Ph.D.'s in this file, 2,395 undertook postdoctoral experience, of whom 1,463, or 61 percent, extended their experience in the same disciplines in which they had studied in graduate school. But the impression that post- doctoral experience is a continuation of graduate education in 61 percent of all cases is misleading, since it is weighted by the fact that more than half of all of those who did experience this continuation were biochemists. If the biochemists are excluded, only 50 percent of the remaining scientists who undertook postdoctoral training did so in their graduate disciplines. Moreover, such an experience is but rarely a mere continuation of graduate education. This is borne out by the following consideration: In a subtile of 3,234 postdoctoral fellows, only 14 percent had taken postdoctoral edu 241

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THE LIFE SCIENCES TABLE 13 Postdoctoral Experience of Scientists in a Limited Group of Biological Disciplines POSTDOCTORAL EXPERIENCE FIELD OF NUMBER IN FIELD OF GRADUATE OF POSTDOCTORAL GRADUATE STUDY Ph.D.'s EXPERIENCE STUDY Number Percent Number Percent ALL BIOLOGY5,7652,395 411,463 61 Anatomy19674 3730 41 Biochemistry1,834968 53752 77 Botany365108 2940 37 Genetics408157 38116 73 Microbiology1,010359 35198 55 Pharmacology374131 3584 64 Physiology805329 40167 50 Zoology773269 3576 28 Source: Survey of Individual Life Scientists, National Academy of Sciences Committee on Research in the Life Sciences. cation in the same university in which they had obtained their doctoral degrees, and only 6 percent in the same departments that had awarded their doctoral degrees. This migratory pattern is particularly evident among the M.D. population. However, about one third of all Ph.D.'s in agriculture and forestry who undertook their postdoctoral training a rather small group-did so in their original universities and, indeed, in the departments that had awarded their degrees. The rather small proportion of students who remained in the same department for postdoctoral study was almost twice as great in public universities as in private universities. In sum, it is clear that the norm for postdoctoral experience, by a wide measure, consists of apprenticeship to a different set of investigators in an environment different from that in which graduate education has been com- pleted. Further, in the experience of our panelists, the current internal heterogeneity of the classical disciplines assured that even the postdoctoral trainee who remains within his original discipline is likely to engage in a problem remote from his graduate research experience. The biochemist who studied intermediary metabolism may later become preoccupied with the mechanism of enzyme action; the physiologist who traced neural path- ways as a graduate student may focus upon ion transport across the nerve membrane during his postdoctoral years. The botanist who was concerned with nutritional requirements for plant growth may later become involved

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THE WORLD OF BIOLOGICAL RESEARCH in the ecology of a cornfield, while the entomologist concerned with pat- terns of insect distribution may switch to a study of insect sex attractants. Intellectual inbreeding is rare in the life sciences community, and the post- doctoral experience is among the chief means of assuring the hybrid vigor of the entire enterprise. A few notes comparing the bioscience subculture with the subcultures of the physical and social sciences may be warranted. The data in support of the following statements are derived largely from the recent National Research Council study of postdoctoral education, The Invisible Univer- sity.* In the nation's leading academic institutions, postdoctoral experience has become the expected prelude to faculty appointment. In recent times, 70 to 80 percent of all initial faculty appointments at such institutions in physics, in chemistry, in biology departments of faculties of arts and sciences, and in the preclinical departments of medical schools have been made to individuals with postdoctoral experience either at the same or at some other institution. In contrast, initial faculty appointments in the social sciences, the humanities, and engineenug relatively rarely require post- doctoral experience. The play of the academic marketplace is such that the frequency of postdoctoral experience among initial appointees to the faculty decreases with the general academic status of the institution. Postdoctoral experience is less frequent among the faculties of "developing" universities, is rare for scientists who are appointed to the faculties of liberal arts col- leges, and is. even less common among those who enter industry. The converse is equally evident; 30 to 40 percent of all relatively young faculty at all universities who have not had postdoctoral experience feel this lack in their current professional lives. In all branches of natural science, promotion up the academic ladder occurs somewhat less rapidly for those who have not had postdoctoral experience, although this may reflect similar appraisal of human potential by the committees who select postdoctoral-fellowship recipients and those who recommend academic promotions, rather than the intellectual rewards of postdoctoral study. These trends are undoubtedly enhanced by the advice given to aspiring scientists by their mentors in graduate school, who strongly urge students in the natural sciences to undertake postdoctoral experience if they aspire to academic careers but rarely do so when this is not the case. In general, such mentors recommend a postdoctoral experience of about two years, with a specific senior scientist in a field somewhat different from that in ' The Invisible University: Postdoctoral Education in the United States, Report of a Study Conducted under the Auspices of the National Research Council, National Academy of Sciences, Washington, D.C., 1969. 243

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244 THE LIFE SCIENCES which the student's dissertation research was conducted, thereby broad- ening his understanding of his discipline. When queried, postdoctoral students advance the same general purpose as their reason for undertaking postdoctoral study, but place more emphasis than do their graduate men- tors upon the acquisition of additional research techniques. Attempts by statistical means to assess the influence on subsequent scien- tific productivity of postdoctoral training are not revealing. Differences among those who took postdoctoral training immediately after graduate school, those who deferred such training for several years, and those who had no such training are trivial when measured by counting numbers of scientific publications, reviews, books written, and similar measures. What cannot be assessed by this means is the quality of the work or its signifi- cance to the field. One indicator has been reported in The Invisible Uni- versity*: the fact that papers published by those who have had postdoctoral experience are cited about twice as frequently in the Citation Index ~ as are papers by those who have not had such experience. Statistically, fre- quency of citation of a paper is some measure of its significance or funda- mentality. It is our contention that, in all scientific fields, scientific bold- ness-willingness to venture beyond the frontier or to undertake large and challenging problems is established relatively early. Certainly, if this is not encouraged in graduate school or in the immediate postdoctoral years, it is rarely evident in subsequent careers. But statistical assessment of this all-important quality is not readily feasible; hence, the enhanced oppor- tunity to develop such habits of mind is another argument that we would advance in support of a year or two of postdoctoral study, preferably Ilot in the same institution or with the same mentor that provided the graduate experience. Data purporting to compare the consequences of graduate or post- doctoral study in the 10 or 20 leading academic institutions with those in other institutions are probably not completely valid. The selection process that operates at the level of admission to graduate school and then to post- doctoral study in the most productive academic laboratories already serves as a screen almost sufficient to assure the ultimate outcome. It is not readily possible to distinguish between the consequences of differences in the quality of the educational experiences in such institutions and the con- sequences of the quality of the initial human input. Certainly it must be undeniable that those most highly qualified will benefit most from a stimu : The Invisible University: Postdoctoral Education in tlze United States, Report of a Study Conducted under the Auspices of the National Research Council, National Academy of Sciences, Washington, D.C., 1969. t Science Citation index; An International Interdisciplinary Index to tlze Literature of Science. (Published by Institute for Scientific Information, Philadelphia.)