Journal of Gerontology 1975, Vol. 30, No. 6, 668-673
Gerontological Research in Psychology Published in the Journal of Gerontology 1963-1974: Perspectives and Progress1
Psychological research on human subjects published in the Journal of Gerontology from 1963 through 1974 was summarized along a variety of dimensions, including subject selection procedures, sample characteristics, data analysis techniques, research design, author characteristics, and area of psychological research. Comparison of 1963-1968 with 1969-1974 showed a dramatic increase in the number of studies analyzing data for sex differences and a lessened concern for the health status of subjects. Studies of intellectual/cognitive functioning clearly dominated, while those measuring a physiological variable increased the most over the 12-year span. Discussion focused on variations among studies on definitions of age, concerns with sample description with respect to health, and sex differences.
to maintain or improve the quality Iit Nisoforder research in adult development and aging occasionally necessary to describe the nature of past research terms of its objectives, context, and current directions. This purpose is served to some extent in the present investigation by sampling research included in the Journal of Gerontology. The scope of the survey is limited to the past 12 years of published papers because it was felt that this was a period of much maturation and increased sophistication within the field of gerontological psychology. The specific focus was to describe the methodological characteristics of the investigations rather than substantive research findings. Previous reviews of aging research have varied along several dimensions. Grofman (1970) reviewed the history of gerontology in Germany, and Adler (1958) focused on the history of the Gerontological Society. Birren (1961) has examined the contributions of various eminent researchers and the influence of various academic and governmental institutions on the field of gerontological
psychology. The work of Riegel (1973) was of importance because it provided an historical perspective and a theoretical and prescriptive framework. Also, chapters which have appeared in the Annual Review of Psychology(Birren, 1960; Botwinick, 1970; Shock, 1951; Chown & Herron, 1965; Lorge, 1956; Schaie & Gribbin, 1975) as well as numerous books, have provided substantive reviews of research in gerontological psychology. Unlike previous reviews, the focus of this study was on the demographic and methodological features of research in gerontological psychology. The Journal of Gerontology was chosen as the data source because of its concern with aging research, including gerontological psychology, and its recognition as one of the most prominent publications in the field of gerontology. The results of this survey are generalizable only to the extent that the articles appearing in the Journal of Gerontology are generalizable to the field of gerontological psychology research as a whole. METHOD
'This research was supported, in part, by a research grant to M.F.E. from NICHD(HD 08220). 'Psychology Dept., Syracuse Univ., 150 Marshall St., Syracuse, NY 13210.
668
The Journal of Gerontology was searched from 1963 through 1974 for articles which were psychological and behavioral in focus and for
Downloaded from http://geronj.oxfordjournals.org/ at Purdue University Libraries ADMN on June 29, 2015
Joel Peter Abrahams, PhD, 2 William J. Hoyer, PhD, 2 Merrill F. Elias, PhD, 2 and Bruce Bradigan, MA2
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY
RESULTS
When the first 6-year period (1963-1968) was compared with the second 6-year period (19691974) several interesting trends were noted. The number of studies employing sex differences analyses increased dramatically during the second 6-year period. In fact, they increased at a greater rate than did the number of studies which used subjects of both sexes. In the first 6 years, 38 of the 105 studies used both male and
female subjects; of these, only 39% (15 studies) analyzed sex differences. During the second 6year period, 43 of the 67 studies used subjects of both sexes; of these, 67.4% (29) analyzed sex differences. The percentage of studies which used both male and female subjects increased from 36.2% during the first 6-year period to 64.2% during the second 6-year period. The health status of the subjects was categorized based on whether it was treated statistically as an independent variable, controlled by the investigator(s), mentioned in terms of the state of the subject, or not mentioned at all. The percentage of studies directly concerned with health as a variable of interest declined slightly from 12.4% (13) in the first 6year period to 10.4% (7) in the second 6-year period. The percentage of studies which attempted to control for health status showed virtually no change (17.1% to 16.4%). However, the percentage of studies stating that the subjects were in "good" or "reasonably good" health declined from 41.9% to 35.8%, and the percentage of studies which failed to mention the health status of the subjects increased from 28.6% to 37.3%. Several trends were also observed for the various content categories of research. Studies of intellectual and cognitive functioning clearly dominated research in gerontological psychology during the past 12 years. This content area increased from 48.6% of the studies in the first 6-year period to 50.7% in the second period. Studies of learning showed a similar increase in the second 6-year period; 21% compared to 19% in the first 6-years. Studies which measured a physiological variable showed the greatest increase. This research category increased from 13.3% during the first 6 years to 21% during the second 6 years. However, studies of perception decreased sharply from 21.9% to 13.4% and clinical studies decreased slightly from 12.4% to 10.4% from the first 6year period to the second. With regard to research design, the crosssectional approach showed a marked increase during the second 6-year period. During the second period, cross-sectional designs accounted for 67.2% of the studies; this compares to 55.2% during the first period. The percentage of studies using a single sample at a single occasion decreased from 38.1% during the first period to only 17.9% during the second period. The use of the longitudinal design increased slightly from 7.6% in the first 6 years to
Downloaded from http://geronj.oxfordjournals.org/ at Purdue University Libraries ADMN on June 29, 2015
which individual response measures were collected on human subjects. Thus, demographic, attitudinal, and theoretical articles were omitted from this survey. Each investigation which met the criteria was then examined for the following information: (a) treatment of health status of subjects; (b) treatment of sex differences; (c) the categories which best described the content of the study; (d) research design and statistical analyses performed; (e) number, sex, and age characteristics of the sample; and (f) number and sex of authors, degrees, and institutional affiliation. Studies were assigned to content categories by extracting key terms from either title or results section. Key words were then used as a guide for the final categories. The nine categories were methodological, physiological (e.g., EEG, GSR, drugs), social (interpersonal behavior), clinical (e.g., organic brain syndrome), intellectual/cognitive (e.g., intelligence, memory, problem solving), learning (e.g., verbal learning, conditioning), psychomotor, perceptual, and industrial. Three methods were used to assign studies to appropriate categories. When the categories were considered orthogonal, only 110 of the studies could be meaningfully assigned. This left 62 studies which could not be classified using an orthogonal system without the intent of the investigators being lost. A double classification system successfully categorized all 172 studies but resulted in 20 separate groups, e.g., clinical-intellectual, physiologicalintellectual, learning-physiological, etc. These groups ranged in size from 1 to 51. Since comparisons between 1963-1968 and 1969-1974 were uninterpretable using a doubleclassification system, a nonorthogonal multiple classification system was used. Thus the categories were not mutually exclusive and many studies did fit into more than one or two groups.
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Table 1. Percentage Comparison of Selected Characteristics of Published Research Between 1963-1968 and 1969-1974.
1963-1968 1969-1974 HEALTH STATUS OF SUBJECTS Studies concerned with health Studies controlling Studies mentioning health of subjects Studies not mentioning health of subjects
12.4% 17.1% 41.9% 28.6%
10.4% 16.4% 35.8% 37.3%
SEX DIFFERENCES Analysis of sex differences Studies using both male and female subjects
39.0% 36.2%
67.4% 64.2%
CONTENT CATEGORIES OF RESEARCH Intellectual/cognitive studies Learning studies Physiological studies Perception studies Clinical studies
48.6% 19.0% 13.3% 21.9% 12.4%
50.7% 21.0% 21.0% 13.4% 10.4%
DESIGN STRATEGIES Cross-sectional studies Longitudinal studies Single sample-single occasion studies
55.2% 7.6% 38.1%
67.2% 10.4% 17.9%
STATISTICAL PROCEDURES Studies using multiple t-tests Studies using multiple ANOVAs
22.9% 10.5%
11.9% 35.8%
AUTHOR CHARACTERISTICS Female Authors Doctoral degrees Academic Institution (Senior author only)
21.5% 78.3% 57.0%
29.5% 74.1% 77.0%
authorships. There were 256 authors of Doctoral status (76.6%), 39 at Masters level (11.6%), and 38 with Bachelors degrees (11.4%). A degree was not reported for one author. Keeping in mind that the content categories were nonorthogonal, there were 85 studies measuring intellectual/cognitive functioning (44.9%), 34 studies concerned with learning (19.8%), 28 studies measuring a physiological variable (16.3%), 31 clinical studies (18%), 32 studies of perception (19.6%), 20 studies of psychomotor performance (11.6%), 11 studies concerned with social variables (6.4%), 9 methodological studies (5.2%), and 3 industrial studies (1.7%). Using the single classification system, there were 51 studies of intellectual/cognitive functioning, 21 learning studies, 18 perception studies, 11 studies of psychomotor performance, 5 clinical studies, 4 social studies, and none that were methodological or industrial. The most common double-classification groups were clinicalintellectual (14 studies), physiologicalintellectual (12), methodological-intellectual (5), and learning-intellectual (5). In 46 of the 83 studies in which both men and women participated, sex differences were statistically analyzed. Additionally, in 6 studies the possibility of sex differences was mentioned but not tested. In 57 studies men only were used; women only were subjects in 11 studies. Only 20 of the 172 investigations analyzed the data for ethnic differences, while 6 mentioned ethnicity as a possible source of variance. Curiously, "old" subjects, i.e., those who comprised the oldest subject sample within a study, ranged in age from as young as 35 to over 100. "Middle-aged" subjects ranged in age from 40 to 70 years of age, while the "young" subjects ranged from 18 to 49 years of age. For example, in 1973 the "old" group in one study ranged from 65 to 80 years, while in another study the "old" group ranged from 51 to 80. With regard to research methodology, there were 52 studies (30.2%) that measured only one group of subjects at one point in time. Only 12 of these occurred during the last 6 years. There were 103 cross-sectional studies (59.8%), 14 longitudinal studies (8.1%), and 3 studies (1.7%) used a cross-sequential strategy. Statistical procedures used by the researchers to analyze the data were grouped into categories. Thirty-eight studies used a single
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10.4% in the second 6 years. No sequential design studies were reported during the first 6 years, but three studies (4.5%) in the second 6 years used these types of data collection strategies. Statistical procedures used during the second 6-year period appeared to demonstrate a higher level of sophistication. In the first period 22.9% of the studies (24) used multiple /-tests to analyze data involving more than two experimental or classificatory conditions. Only 11.9% (8) did so in the second period. There was a corresponding increase in the percentage of studies using multiple univariate analyses of variance; 10.5% (11) in the first 6 years compared to 35.8% (24) in the second 6 years. Author characteristics showed several changes between the first and second 6-year periods. The frequency of female (co)authorship increased from 21.5% in the first period to 29.5% in the second period. There was an increasing trend for the senior author to be from an academic rather than a government or service delivery institution. For the first 6-year period the academic/nonacademic ratio was 57/43. This ratio increased sharply during the econd 6-year period to 77/23. Percentage comparison of selected characteristics are shown in Table 1. Analyzing across years, there were 172 studies by a total of 334 authors; 64 were singleauthor studies, the remaining studies had from 2 to 6 authors. Women comprised 25% of the total author sample and 26.5% of the 64 single
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY
DISCUSSION
Several broad issues are raised by the survey of the past 12 years of human behavioral research in gerontological psychology as respresented by publications in the Journal of Gerontology. One issue is the composition and the characteristics of the samples. There has been little consensus regarding the definition of "old," "middle-aged," and "young." Obviously when "middle-aged" as an age range in one investigation falls completely within the older age range of another study, the terms young, middle-aged, and old become useless as absolute descriptive classes. Even if the age ranges were mutually exclusive, in certain instances their usefulness would be limited. This is particularly true where cohort-specific differences were more important than maturation. However, it would be quite useful if some minimal criteria were to be established for age grouping and for age labels, particularly at the upper end of the life-span. Authors should specify clearly the age characteristics of the samples under investigation, e.g., in figures, tables, and text, by descriptive statistics, e.g., median ages, rather than by labels such as "young" and "old." A second issue is the apparent lack of adequate control of the health status of the subjects. Health status is a most potent subject characteristic influencing age-associated psychological performance (Spieth, 1965). Birren, Butler, Greenhouse, Sokoloff, and Yarrow (1963), Wilkie and Eisdorfer (1973), and others have clearly demonstrated the negative effect of the presence of even mild chronic disease or sensory impairment on a variety of psychological measures, particularly psychomotor performance and intellectual functioning. A failure to consider accurately health status can lead to over-estimation of the fluence of chronological age on a dependent variable.
Only \6°7o-ll% of the 172 studies surveyed controlled for health variables. Excluding the 20 studies directly concerned with health status, only 19.1% of the remaining studies controlled for health of subjects. Equally disquieting was the observation of a decrease in the percentage of studies mentioning that the subjects were in "good" or "reasonably good" health and the concomitant increased percentage of studies which failed to make any mention of health of subjects. Assuming that participants in those studies which did not even mention health status were in good or reasonably good health, there would still be a large variation in health status from study to study and within a single study. This problem increases when subjects are recruited from a variety of settings. Researchers have demonstrated a relationship between speed of response and the coronary-prone behavior pattern in healthy middle-aged males (Abrahams & Birren, 1973) and self-report of cardiovascular symptoms in ostensively healthy elderly subjects (Botwinick & Storandt, 1974). While the ideal situation would involve the medical screening of middle-aged and elderly subjects, screening is probably not practical for most investigators. However, some form of health assessment should be undertaken where it is known or suspected that disease states influence age-associated performance. For example, the relationship between speed and timing of behavior and measurement of intellectual performance abilities would appear to necessitate some control or at least comparison of health status in intellectual/cognitive studies. Unfortunately, in the second 6-year period only five of the 32 studies of intellectual/cognitive functioning controlled for health status of subjects. A third issue was the analysis of sex differences. During the second 6-year period the percentage of studies which tested for sex differences increased more than did the percentage of studies which used both male and female subjects. However, one-third of the studies using subjects of both sexes failed to analyze the data for any sex differences. Since certain intellectual abilities may be sex-linked, e.g., spatial relations (Nash, 1970) or the result of sex-related stereotypes and differences in experience, the question of gender differences would seem to be quite important. Thus, it is recommended that gender differences be treated, conceptually and statistically, as
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univariate analysis of variance, or covariance, or contrast; 6 studies used a multivariate analysis of variance; 28 studies used some form of nonparametric procedures; 32 used multiple analyses of variance; 21 used correlational or regression techniques; and 7 used factor analytic procedures. Additionally, only 11 studies (7 in the last 6 years) provided an estimate of the proportion of variance accounted for in the dependent variable by the independent variable, e.g., omega squared (Hays, 1963).
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Another point which became apparent was the infrequent use of multivariate analysis of variance (MANOVA) and multivariate procedures in general. The MANOVA may be used as a protection against chance differences resulting from application of univariate ANOVAs to multiple dependent variables and as a means of constructing meaningful composite scores (Elias, in press; Tatsuoka, 1971). Compared to the number of studies which used multiple ANOVAs, the percentage which used MANOVA was very small. Undoubtedly, the unavailability of computer programs for multivariate procedures severely limited the number of applications of MANOVA designs and analyses during the first 6-year period. However, this cannot be said of the second period. MANOVA and other multivariate programs (e.g., Clyde Computing Service) have become increasingly available, and it is suggested that where appropriate, future authors make greater use of multivariate procedures. Although statistics may be the bane of existence for many researchers, appropriate use of multivariate procedures could prove to be a most useful research tool. It was quite encouraging to note that the over-all statistical sophistication of investigators in gerontological psychology has risen decidedly during the past 12 years. The great reduction in the use of multiple /-tests in the absence of over-all ANOVAs, the increased use of factorial designs, the increased use of omega squared, and to a significantly lesser ex-
tent, increased use of MANOVA procedures attest to a higher level of sophistication. Intellectual/cognitive functioning has continued as the dominant area of research interest in gerontological psychology. This no doubt reflects the large number of abilities and skills included by the term intellectual/cognitive functioning, the large number of measurement instruments available, and the large number of variables known to affect intellectual and cognitive performance. As the data base and the level of methodological sophistication have increased, the parameters of adult intellectual performance, memory, and problem solving have become more clearly delineated; but in view of increased knowledge, there has also been a need to re-examine previous assumptions (e.g., irreversible decrement) regarding intellectual/cognitive functioning. The results obtained with regard to gender and the academic degrees of authors were not surprising. As is the case in other areas of psychology, journal contributors are predominantly male and hold Doctoral degrees. However, it was quite surprising to observe what could only be termed an exodus of researchers publishing behavioral studies on humans away from governmental and service delivery organizations to academic institutions. This movement clearly began with studies published in 1969 and has continued since. The origin of this change in senior author affiliation could not be determined from the data. However, this shift may have resulted from the establishment of gerontology centers at universities and a movement of some well-established researchers from government to academia. During the past 12 years the entire field of gerontological psychology has grown tremendously. There has been a vast increase in the data base and level of methodological sophistication. This trend is evidenced by changes in several areas. There was a sharp drop in the frequency of the single samplesingle occasion studies during the second 6-year period. The field of gerontological psychology apparently has moved away from simply describing the psychological characteristics of aged samples toward the task of explaining observed age-associated differences or changes in psychological functioning. Even within the behavioral sciences, the psychology of adult development and aging is a relatively new discipline. As is true with any newly evolved area that cannot draw directly from existing
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sources of variance in future gerontological research in psychology. With respect to the statistical methods employed by the investigators, several points became apparent. First, only 11 studies during the entire 12 years estimated the proportion of varience accounted for by the independent variable (omega squared). In some instances this may be of greater importance than statistical significance. Achieving statistical significance does not indicate the strength of association between the independent and the dependent variables. This becomes increasingly crucial as the size of the sample increases. Considering the number of studies which employed ANOVA designs, the failure to report an estimate of variance accounted for is indeed surprising. One could only urge that future authors who employ designs amenable to estimates of proportion of variance accounted for, do so.
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY knowledge bases, there is of necessity a descriptive phase. As knowledge accrues, explanation becomes a more major concern. SUMMARY
REFERENCES
Abrahams, J. P., & Birren, J. E. Reaction time as a function of age and behavioral predisposition to coronary heart disease. Journal of Gerontology, 1973, 28, 471478. Adler, M. History of the Gerontological Society. Journal of Gerontology, 1958,13, 94-100. Birren, J. E. Psychological aspects of aging. In P. R. Farnsworth and Q. McNemar (Eds.), Annual Review of Psychology, 1960,11, 161-198. Birren, J. E. A brief history of the psychology of aging. Gerontologist, 1961,1, 69-77,127-139. Birren, J. E., Butler, R. N., Greenhouse, S. W., Sokoloff, L., & yarrow, M. R. (Eds.), Human Aging. Public Health Service, Washington, 1963. Botwinick, J. Gero-psychology. In P. H. Mussen & M. R. Rosenzweig (Eds.), Annual Review of Psychology, 1970,27,239-272.
Botwinick, J. & Storandt, M. Cardiovascular status, depressive affect, and other factors in reaction time. Journal of Gerontology, 1974,29, 543-548. Chown, S. M., & herron, A. Psychological aspects of aging in man. In P. R. Fransworth, O. McNemar, & Q. McNemar (Eds.), Annual Review of Psychology, 1965, 16, 417-450. Clyde, D. J. Multivariate analysis of variance on large computers. Clyde Computing Service, Miami, 1969. Elias, M. F. Potential applications of multivariate analysis of variance to psychopharmacological research. In B. E. Elftheriou (Ed.), Psychopharmicogenetics. Plenum Press, New York, (in press) Groffman, K. J. Life-span developmental psychology in Germany: Past and present. In L. R. Goulet & P. B. Bakes (Eds.), Life-span developmental psychology: Research and theory. Academic Press, New York, 1970. Hays, W. L. Statistics for psychologists. Holt, New York, 1963. Lorge, I. Gerontology (Later Maturity). In P. R. Farnsworth & Q. McNemar (Eds.), Annual Review of Psychology, 1956, 7, 349-364. Nash, J. Sex differences and their origins. In J. Nash (Ed.), Deverlopmental psychology: A psychobiological approach. Prentice-Hall, Englewood Cliffs, 1970. Riegel, K. F. On the history of psychological gerontology. In C. Eisdorfer & M. P. Lawton (Eds.), Psychology of adult development and aging. American Psychological Assn., Washington, 1973. Schaie, K. W., & Gribbin, K. Adult development and aging. In M. R. Rosenzweig & L. W. Porter (Eds.), Annual Review of Psychology, 1975,26, 65-96. Shock, N. W. Gerontology (Later Maturity). In C. P. Stone & D. W. Taylor (Eds.), Annual Review of Psychology, 1951,2,353-370. Spieth, W. Slowness of task performance and cardiovascular disease. In A. T. Welford & J. E. Birren (Eds.), Behavior, aging and the nervous system. Charles C Thomas, Springfield, 1965. Tatsuoka, M. M., Multivariate analysis: Techniques for educational and psychological research. Wiley, New York, 1971. Wilkie, F. & Eisdorfer, C. Systemic disease and behavioral correlates. In L. F. Jarvik, C. Eisdorfer, & J. E. Blum (Eds.), Intellectual functioning in adults. Springer, New York, 1973.
Downloaded from http://geronj.oxfordjournals.org/ at Purdue University Libraries ADMN on June 29, 2015
Psychological research measuring overt behavioral responses from human subjects published in the Journal of Gerontology from 1963 through 1974 were surveyed. The studies were summarized along a variety of dimensions including subject selection procedures and sample characteristics, statistical procedures, design strategies, area of psychological research, and author characteristics. Discussion focused on trends in regard to the treatment of sex differences and health status of the subjects. Finally, recommendations were made concerning the treatment of health status, gender, and age as variables, and the use of omega squared or other estimates of proportion of variance accounted for in gerontological research in psychology.
673
Gerontological Research in Psychology Published in the Journal of Gerontology 1963-1974: Perspectives and Progress1
Psychological research on human subjects published in the Journal of Gerontology from 1963 through 1974 was summarized along a variety of dimensions, including subject selection procedures, sample characteristics, data analysis techniques, research design, author characteristics, and area of psychological research. Comparison of 1963-1968 with 1969-1974 showed a dramatic increase in the number of studies analyzing data for sex differences and a lessened concern for the health status of subjects. Studies of intellectual/cognitive functioning clearly dominated, while those measuring a physiological variable increased the most over the 12-year span. Discussion focused on variations among studies on definitions of age, concerns with sample description with respect to health, and sex differences.
to maintain or improve the quality Iit Nisoforder research in adult development and aging occasionally necessary to describe the nature of past research terms of its objectives, context, and current directions. This purpose is served to some extent in the present investigation by sampling research included in the Journal of Gerontology. The scope of the survey is limited to the past 12 years of published papers because it was felt that this was a period of much maturation and increased sophistication within the field of gerontological psychology. The specific focus was to describe the methodological characteristics of the investigations rather than substantive research findings. Previous reviews of aging research have varied along several dimensions. Grofman (1970) reviewed the history of gerontology in Germany, and Adler (1958) focused on the history of the Gerontological Society. Birren (1961) has examined the contributions of various eminent researchers and the influence of various academic and governmental institutions on the field of gerontological
psychology. The work of Riegel (1973) was of importance because it provided an historical perspective and a theoretical and prescriptive framework. Also, chapters which have appeared in the Annual Review of Psychology(Birren, 1960; Botwinick, 1970; Shock, 1951; Chown & Herron, 1965; Lorge, 1956; Schaie & Gribbin, 1975) as well as numerous books, have provided substantive reviews of research in gerontological psychology. Unlike previous reviews, the focus of this study was on the demographic and methodological features of research in gerontological psychology. The Journal of Gerontology was chosen as the data source because of its concern with aging research, including gerontological psychology, and its recognition as one of the most prominent publications in the field of gerontology. The results of this survey are generalizable only to the extent that the articles appearing in the Journal of Gerontology are generalizable to the field of gerontological psychology research as a whole. METHOD
'This research was supported, in part, by a research grant to M.F.E. from NICHD(HD 08220). 'Psychology Dept., Syracuse Univ., 150 Marshall St., Syracuse, NY 13210.
668
The Journal of Gerontology was searched from 1963 through 1974 for articles which were psychological and behavioral in focus and for
Downloaded from http://geronj.oxfordjournals.org/ at Purdue University Libraries ADMN on June 29, 2015
Joel Peter Abrahams, PhD, 2 William J. Hoyer, PhD, 2 Merrill F. Elias, PhD, 2 and Bruce Bradigan, MA2
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY
RESULTS
When the first 6-year period (1963-1968) was compared with the second 6-year period (19691974) several interesting trends were noted. The number of studies employing sex differences analyses increased dramatically during the second 6-year period. In fact, they increased at a greater rate than did the number of studies which used subjects of both sexes. In the first 6 years, 38 of the 105 studies used both male and
female subjects; of these, only 39% (15 studies) analyzed sex differences. During the second 6year period, 43 of the 67 studies used subjects of both sexes; of these, 67.4% (29) analyzed sex differences. The percentage of studies which used both male and female subjects increased from 36.2% during the first 6-year period to 64.2% during the second 6-year period. The health status of the subjects was categorized based on whether it was treated statistically as an independent variable, controlled by the investigator(s), mentioned in terms of the state of the subject, or not mentioned at all. The percentage of studies directly concerned with health as a variable of interest declined slightly from 12.4% (13) in the first 6year period to 10.4% (7) in the second 6-year period. The percentage of studies which attempted to control for health status showed virtually no change (17.1% to 16.4%). However, the percentage of studies stating that the subjects were in "good" or "reasonably good" health declined from 41.9% to 35.8%, and the percentage of studies which failed to mention the health status of the subjects increased from 28.6% to 37.3%. Several trends were also observed for the various content categories of research. Studies of intellectual and cognitive functioning clearly dominated research in gerontological psychology during the past 12 years. This content area increased from 48.6% of the studies in the first 6-year period to 50.7% in the second period. Studies of learning showed a similar increase in the second 6-year period; 21% compared to 19% in the first 6-years. Studies which measured a physiological variable showed the greatest increase. This research category increased from 13.3% during the first 6 years to 21% during the second 6 years. However, studies of perception decreased sharply from 21.9% to 13.4% and clinical studies decreased slightly from 12.4% to 10.4% from the first 6year period to the second. With regard to research design, the crosssectional approach showed a marked increase during the second 6-year period. During the second period, cross-sectional designs accounted for 67.2% of the studies; this compares to 55.2% during the first period. The percentage of studies using a single sample at a single occasion decreased from 38.1% during the first period to only 17.9% during the second period. The use of the longitudinal design increased slightly from 7.6% in the first 6 years to
Downloaded from http://geronj.oxfordjournals.org/ at Purdue University Libraries ADMN on June 29, 2015
which individual response measures were collected on human subjects. Thus, demographic, attitudinal, and theoretical articles were omitted from this survey. Each investigation which met the criteria was then examined for the following information: (a) treatment of health status of subjects; (b) treatment of sex differences; (c) the categories which best described the content of the study; (d) research design and statistical analyses performed; (e) number, sex, and age characteristics of the sample; and (f) number and sex of authors, degrees, and institutional affiliation. Studies were assigned to content categories by extracting key terms from either title or results section. Key words were then used as a guide for the final categories. The nine categories were methodological, physiological (e.g., EEG, GSR, drugs), social (interpersonal behavior), clinical (e.g., organic brain syndrome), intellectual/cognitive (e.g., intelligence, memory, problem solving), learning (e.g., verbal learning, conditioning), psychomotor, perceptual, and industrial. Three methods were used to assign studies to appropriate categories. When the categories were considered orthogonal, only 110 of the studies could be meaningfully assigned. This left 62 studies which could not be classified using an orthogonal system without the intent of the investigators being lost. A double classification system successfully categorized all 172 studies but resulted in 20 separate groups, e.g., clinical-intellectual, physiologicalintellectual, learning-physiological, etc. These groups ranged in size from 1 to 51. Since comparisons between 1963-1968 and 1969-1974 were uninterpretable using a doubleclassification system, a nonorthogonal multiple classification system was used. Thus the categories were not mutually exclusive and many studies did fit into more than one or two groups.
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Table 1. Percentage Comparison of Selected Characteristics of Published Research Between 1963-1968 and 1969-1974.
1963-1968 1969-1974 HEALTH STATUS OF SUBJECTS Studies concerned with health Studies controlling Studies mentioning health of subjects Studies not mentioning health of subjects
12.4% 17.1% 41.9% 28.6%
10.4% 16.4% 35.8% 37.3%
SEX DIFFERENCES Analysis of sex differences Studies using both male and female subjects
39.0% 36.2%
67.4% 64.2%
CONTENT CATEGORIES OF RESEARCH Intellectual/cognitive studies Learning studies Physiological studies Perception studies Clinical studies
48.6% 19.0% 13.3% 21.9% 12.4%
50.7% 21.0% 21.0% 13.4% 10.4%
DESIGN STRATEGIES Cross-sectional studies Longitudinal studies Single sample-single occasion studies
55.2% 7.6% 38.1%
67.2% 10.4% 17.9%
STATISTICAL PROCEDURES Studies using multiple t-tests Studies using multiple ANOVAs
22.9% 10.5%
11.9% 35.8%
AUTHOR CHARACTERISTICS Female Authors Doctoral degrees Academic Institution (Senior author only)
21.5% 78.3% 57.0%
29.5% 74.1% 77.0%
authorships. There were 256 authors of Doctoral status (76.6%), 39 at Masters level (11.6%), and 38 with Bachelors degrees (11.4%). A degree was not reported for one author. Keeping in mind that the content categories were nonorthogonal, there were 85 studies measuring intellectual/cognitive functioning (44.9%), 34 studies concerned with learning (19.8%), 28 studies measuring a physiological variable (16.3%), 31 clinical studies (18%), 32 studies of perception (19.6%), 20 studies of psychomotor performance (11.6%), 11 studies concerned with social variables (6.4%), 9 methodological studies (5.2%), and 3 industrial studies (1.7%). Using the single classification system, there were 51 studies of intellectual/cognitive functioning, 21 learning studies, 18 perception studies, 11 studies of psychomotor performance, 5 clinical studies, 4 social studies, and none that were methodological or industrial. The most common double-classification groups were clinicalintellectual (14 studies), physiologicalintellectual (12), methodological-intellectual (5), and learning-intellectual (5). In 46 of the 83 studies in which both men and women participated, sex differences were statistically analyzed. Additionally, in 6 studies the possibility of sex differences was mentioned but not tested. In 57 studies men only were used; women only were subjects in 11 studies. Only 20 of the 172 investigations analyzed the data for ethnic differences, while 6 mentioned ethnicity as a possible source of variance. Curiously, "old" subjects, i.e., those who comprised the oldest subject sample within a study, ranged in age from as young as 35 to over 100. "Middle-aged" subjects ranged in age from 40 to 70 years of age, while the "young" subjects ranged from 18 to 49 years of age. For example, in 1973 the "old" group in one study ranged from 65 to 80 years, while in another study the "old" group ranged from 51 to 80. With regard to research methodology, there were 52 studies (30.2%) that measured only one group of subjects at one point in time. Only 12 of these occurred during the last 6 years. There were 103 cross-sectional studies (59.8%), 14 longitudinal studies (8.1%), and 3 studies (1.7%) used a cross-sequential strategy. Statistical procedures used by the researchers to analyze the data were grouped into categories. Thirty-eight studies used a single
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10.4% in the second 6 years. No sequential design studies were reported during the first 6 years, but three studies (4.5%) in the second 6 years used these types of data collection strategies. Statistical procedures used during the second 6-year period appeared to demonstrate a higher level of sophistication. In the first period 22.9% of the studies (24) used multiple /-tests to analyze data involving more than two experimental or classificatory conditions. Only 11.9% (8) did so in the second period. There was a corresponding increase in the percentage of studies using multiple univariate analyses of variance; 10.5% (11) in the first 6 years compared to 35.8% (24) in the second 6 years. Author characteristics showed several changes between the first and second 6-year periods. The frequency of female (co)authorship increased from 21.5% in the first period to 29.5% in the second period. There was an increasing trend for the senior author to be from an academic rather than a government or service delivery institution. For the first 6-year period the academic/nonacademic ratio was 57/43. This ratio increased sharply during the econd 6-year period to 77/23. Percentage comparison of selected characteristics are shown in Table 1. Analyzing across years, there were 172 studies by a total of 334 authors; 64 were singleauthor studies, the remaining studies had from 2 to 6 authors. Women comprised 25% of the total author sample and 26.5% of the 64 single
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY
DISCUSSION
Several broad issues are raised by the survey of the past 12 years of human behavioral research in gerontological psychology as respresented by publications in the Journal of Gerontology. One issue is the composition and the characteristics of the samples. There has been little consensus regarding the definition of "old," "middle-aged," and "young." Obviously when "middle-aged" as an age range in one investigation falls completely within the older age range of another study, the terms young, middle-aged, and old become useless as absolute descriptive classes. Even if the age ranges were mutually exclusive, in certain instances their usefulness would be limited. This is particularly true where cohort-specific differences were more important than maturation. However, it would be quite useful if some minimal criteria were to be established for age grouping and for age labels, particularly at the upper end of the life-span. Authors should specify clearly the age characteristics of the samples under investigation, e.g., in figures, tables, and text, by descriptive statistics, e.g., median ages, rather than by labels such as "young" and "old." A second issue is the apparent lack of adequate control of the health status of the subjects. Health status is a most potent subject characteristic influencing age-associated psychological performance (Spieth, 1965). Birren, Butler, Greenhouse, Sokoloff, and Yarrow (1963), Wilkie and Eisdorfer (1973), and others have clearly demonstrated the negative effect of the presence of even mild chronic disease or sensory impairment on a variety of psychological measures, particularly psychomotor performance and intellectual functioning. A failure to consider accurately health status can lead to over-estimation of the fluence of chronological age on a dependent variable.
Only \6°7o-ll% of the 172 studies surveyed controlled for health variables. Excluding the 20 studies directly concerned with health status, only 19.1% of the remaining studies controlled for health of subjects. Equally disquieting was the observation of a decrease in the percentage of studies mentioning that the subjects were in "good" or "reasonably good" health and the concomitant increased percentage of studies which failed to make any mention of health of subjects. Assuming that participants in those studies which did not even mention health status were in good or reasonably good health, there would still be a large variation in health status from study to study and within a single study. This problem increases when subjects are recruited from a variety of settings. Researchers have demonstrated a relationship between speed of response and the coronary-prone behavior pattern in healthy middle-aged males (Abrahams & Birren, 1973) and self-report of cardiovascular symptoms in ostensively healthy elderly subjects (Botwinick & Storandt, 1974). While the ideal situation would involve the medical screening of middle-aged and elderly subjects, screening is probably not practical for most investigators. However, some form of health assessment should be undertaken where it is known or suspected that disease states influence age-associated performance. For example, the relationship between speed and timing of behavior and measurement of intellectual performance abilities would appear to necessitate some control or at least comparison of health status in intellectual/cognitive studies. Unfortunately, in the second 6-year period only five of the 32 studies of intellectual/cognitive functioning controlled for health status of subjects. A third issue was the analysis of sex differences. During the second 6-year period the percentage of studies which tested for sex differences increased more than did the percentage of studies which used both male and female subjects. However, one-third of the studies using subjects of both sexes failed to analyze the data for any sex differences. Since certain intellectual abilities may be sex-linked, e.g., spatial relations (Nash, 1970) or the result of sex-related stereotypes and differences in experience, the question of gender differences would seem to be quite important. Thus, it is recommended that gender differences be treated, conceptually and statistically, as
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univariate analysis of variance, or covariance, or contrast; 6 studies used a multivariate analysis of variance; 28 studies used some form of nonparametric procedures; 32 used multiple analyses of variance; 21 used correlational or regression techniques; and 7 used factor analytic procedures. Additionally, only 11 studies (7 in the last 6 years) provided an estimate of the proportion of variance accounted for in the dependent variable by the independent variable, e.g., omega squared (Hays, 1963).
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Another point which became apparent was the infrequent use of multivariate analysis of variance (MANOVA) and multivariate procedures in general. The MANOVA may be used as a protection against chance differences resulting from application of univariate ANOVAs to multiple dependent variables and as a means of constructing meaningful composite scores (Elias, in press; Tatsuoka, 1971). Compared to the number of studies which used multiple ANOVAs, the percentage which used MANOVA was very small. Undoubtedly, the unavailability of computer programs for multivariate procedures severely limited the number of applications of MANOVA designs and analyses during the first 6-year period. However, this cannot be said of the second period. MANOVA and other multivariate programs (e.g., Clyde Computing Service) have become increasingly available, and it is suggested that where appropriate, future authors make greater use of multivariate procedures. Although statistics may be the bane of existence for many researchers, appropriate use of multivariate procedures could prove to be a most useful research tool. It was quite encouraging to note that the over-all statistical sophistication of investigators in gerontological psychology has risen decidedly during the past 12 years. The great reduction in the use of multiple /-tests in the absence of over-all ANOVAs, the increased use of factorial designs, the increased use of omega squared, and to a significantly lesser ex-
tent, increased use of MANOVA procedures attest to a higher level of sophistication. Intellectual/cognitive functioning has continued as the dominant area of research interest in gerontological psychology. This no doubt reflects the large number of abilities and skills included by the term intellectual/cognitive functioning, the large number of measurement instruments available, and the large number of variables known to affect intellectual and cognitive performance. As the data base and the level of methodological sophistication have increased, the parameters of adult intellectual performance, memory, and problem solving have become more clearly delineated; but in view of increased knowledge, there has also been a need to re-examine previous assumptions (e.g., irreversible decrement) regarding intellectual/cognitive functioning. The results obtained with regard to gender and the academic degrees of authors were not surprising. As is the case in other areas of psychology, journal contributors are predominantly male and hold Doctoral degrees. However, it was quite surprising to observe what could only be termed an exodus of researchers publishing behavioral studies on humans away from governmental and service delivery organizations to academic institutions. This movement clearly began with studies published in 1969 and has continued since. The origin of this change in senior author affiliation could not be determined from the data. However, this shift may have resulted from the establishment of gerontology centers at universities and a movement of some well-established researchers from government to academia. During the past 12 years the entire field of gerontological psychology has grown tremendously. There has been a vast increase in the data base and level of methodological sophistication. This trend is evidenced by changes in several areas. There was a sharp drop in the frequency of the single samplesingle occasion studies during the second 6-year period. The field of gerontological psychology apparently has moved away from simply describing the psychological characteristics of aged samples toward the task of explaining observed age-associated differences or changes in psychological functioning. Even within the behavioral sciences, the psychology of adult development and aging is a relatively new discipline. As is true with any newly evolved area that cannot draw directly from existing
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sources of variance in future gerontological research in psychology. With respect to the statistical methods employed by the investigators, several points became apparent. First, only 11 studies during the entire 12 years estimated the proportion of varience accounted for by the independent variable (omega squared). In some instances this may be of greater importance than statistical significance. Achieving statistical significance does not indicate the strength of association between the independent and the dependent variables. This becomes increasingly crucial as the size of the sample increases. Considering the number of studies which employed ANOVA designs, the failure to report an estimate of variance accounted for is indeed surprising. One could only urge that future authors who employ designs amenable to estimates of proportion of variance accounted for, do so.
GERONTOLOGICAL RESEARCH IN PSYCHOLOGY knowledge bases, there is of necessity a descriptive phase. As knowledge accrues, explanation becomes a more major concern. SUMMARY
REFERENCES
Abrahams, J. P., & Birren, J. E. Reaction time as a function of age and behavioral predisposition to coronary heart disease. Journal of Gerontology, 1973, 28, 471478. Adler, M. History of the Gerontological Society. Journal of Gerontology, 1958,13, 94-100. Birren, J. E. Psychological aspects of aging. In P. R. Farnsworth and Q. McNemar (Eds.), Annual Review of Psychology, 1960,11, 161-198. Birren, J. E. A brief history of the psychology of aging. Gerontologist, 1961,1, 69-77,127-139. Birren, J. E., Butler, R. N., Greenhouse, S. W., Sokoloff, L., & yarrow, M. R. (Eds.), Human Aging. Public Health Service, Washington, 1963. Botwinick, J. Gero-psychology. In P. H. Mussen & M. R. Rosenzweig (Eds.), Annual Review of Psychology, 1970,27,239-272.
Botwinick, J. & Storandt, M. Cardiovascular status, depressive affect, and other factors in reaction time. Journal of Gerontology, 1974,29, 543-548. Chown, S. M., & herron, A. Psychological aspects of aging in man. In P. R. Fransworth, O. McNemar, & Q. McNemar (Eds.), Annual Review of Psychology, 1965, 16, 417-450. Clyde, D. J. Multivariate analysis of variance on large computers. Clyde Computing Service, Miami, 1969. Elias, M. F. Potential applications of multivariate analysis of variance to psychopharmacological research. In B. E. Elftheriou (Ed.), Psychopharmicogenetics. Plenum Press, New York, (in press) Groffman, K. J. Life-span developmental psychology in Germany: Past and present. In L. R. Goulet & P. B. Bakes (Eds.), Life-span developmental psychology: Research and theory. Academic Press, New York, 1970. Hays, W. L. Statistics for psychologists. Holt, New York, 1963. Lorge, I. Gerontology (Later Maturity). In P. R. Farnsworth & Q. McNemar (Eds.), Annual Review of Psychology, 1956, 7, 349-364. Nash, J. Sex differences and their origins. In J. Nash (Ed.), Deverlopmental psychology: A psychobiological approach. Prentice-Hall, Englewood Cliffs, 1970. Riegel, K. F. On the history of psychological gerontology. In C. Eisdorfer & M. P. Lawton (Eds.), Psychology of adult development and aging. American Psychological Assn., Washington, 1973. Schaie, K. W., & Gribbin, K. Adult development and aging. In M. R. Rosenzweig & L. W. Porter (Eds.), Annual Review of Psychology, 1975,26, 65-96. Shock, N. W. Gerontology (Later Maturity). In C. P. Stone & D. W. Taylor (Eds.), Annual Review of Psychology, 1951,2,353-370. Spieth, W. Slowness of task performance and cardiovascular disease. In A. T. Welford & J. E. Birren (Eds.), Behavior, aging and the nervous system. Charles C Thomas, Springfield, 1965. Tatsuoka, M. M., Multivariate analysis: Techniques for educational and psychological research. Wiley, New York, 1971. Wilkie, F. & Eisdorfer, C. Systemic disease and behavioral correlates. In L. F. Jarvik, C. Eisdorfer, & J. E. Blum (Eds.), Intellectual functioning in adults. Springer, New York, 1973.
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Psychological research measuring overt behavioral responses from human subjects published in the Journal of Gerontology from 1963 through 1974 were surveyed. The studies were summarized along a variety of dimensions including subject selection procedures and sample characteristics, statistical procedures, design strategies, area of psychological research, and author characteristics. Discussion focused on trends in regard to the treatment of sex differences and health status of the subjects. Finally, recommendations were made concerning the treatment of health status, gender, and age as variables, and the use of omega squared or other estimates of proportion of variance accounted for in gerontological research in psychology.
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