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Library Philosophy and Practice 2010

ISSN 1522-0222

Citations in Psychology PhD Theses: An Obsolescence Study

Dr. N. Zafrunnisha
Librarian, CVR College of Engineering
Hyderabad, Andhra Pradesh, India

Prof. V. Pulla Reddy
Dept. of Library and Information Science
S.V. University
Tirupati, Andhra Pradesh, India

 

Introduction

Obsolescence studies are one of the main areas of bibliometrics and infometrics. Obsolescence is a vital aspect of scientific literature. Growth and obsolescence are usually considered together, because they represent the initial and final stages of the information cycle. Growth studies investigate patterns in the creation of literature over time.

An obsolescence study could be treated as an aspect of citation analysis for journal articles. Obsolescence studies are useful for researchers, librarians, and decision-makers in information centers. They are also helpful for pioneers in a scientific discipline to know how far they must go back to obtain material in their field of interest.

Scope

The present study attempts to discover the obsolescence rate of psychology literature cited in the doctoral theses awarded from 1963 to 2005, at S.V. University, Tirupati, Osmania University, Hyderabad, and Andhra University, Visakhapattanam. The study focuses on the citations included in doctoral theses awarded in psychology.

Objectives

The objectives of the present study are to discover:

The objectives of the present study are to discover:

  • Chronological distribution of journal citations
  • Obsolescence and half-life of psychology journals
  • Chronological distribution of book citations
  • Obsolescence and half-life of psychology book citations.

Material and Methods

The doctoral theses which are the products of research activity were examined for the study: 141 theses in psychology, accepted between 1963-2005 by Sri Venkateswara University,Tirupati, Osmania University, Hyderabad, and Andhra University, Visakhapattanam. The total number of journal and book citations found in those theses is 14,374 and 7,110.

The analysis of different characteristics of the literature was carried out on the citations. Number of authors, bibliographic format, year of publication, journal name, subject, country, language, and publisher's name were recorded.

The data was analyzed using Microsoft Excel and the Statistical Package for the Social Sciences (SPSS).

Review of Literature

Obsolescence is defined as the decline over time in the validity or utility of information. Studies of aging or obsolescence of documents commonly assess the decline in the use of a representative set of documents over time. Growth in the literature of a particular field plays an important role in age distribution.

Such studies help librarians decide which documents to keep or discard. To compare the speed of decay in different subjects, “half-life” is used as a measure. Half-life refers to the time during which one half of the current active literature was published.

The study of age of literature basing on citations has a long history. The age of the literature has been analysed in physics (Hooker 1935), speech literature (Brodus 1953), physiology (Lowler 1963), sociology (Lin and Nelson 1969), English literature (Heinzkill 1980), and mathematics (Line 1972). Other studies include chemistry (Brown 1980, Aruna 1999), biological sciences (Vimala 1997), and geology (Mahapatra and Bhagavan 2000).

Results and Discussion

Table 1 presents the obsolescence rate of literature in psychology.

Table: 1: Citation frequency of journals and books in psychology

JOURNALS BOOKS
Age (t) No. of citations Cumulative no. of citations Cumulative Percentage No. of Citations Cumulative no. of citations Cumulative percentage
1 2 3 4 5 6 7
0 61 61 0.42 43 43 0.60
1 163 224 1.56 50 93 1.31
2 323 547 3.81 84 177 2.49
3 406 953 6.63 133 310 4.36
4 569 1522 10.59 156 466 6.55
5 530 2052 14.28 178 644 9.06
6 582 2634 18.32 144 788 11.08
7 614 3248 22.60 192 980 13.78
8 598 3846 26.76 235 1215 17.09
9 586 4432 30.83 221 1436 20.20
10 571 5003 34.81 232 1668 23.46
11 593 5596 38.93 257 1925 27.07
12 601 6197 43.11 229 2154 30.30
13 545 6742 46.90 211 2365 33.26
14 541 7283 50.67 265 2630 36.99
15 577 7860 54.68 207 2837 39.90
16 503 8363 58.18 211 3048 42.87
17 435 8798 61.21 194 3242 45.60
18 449 9247 64.33 222 3464 48.72
19 410 9657 67.18 191 3655 51.41
20 375 10032 69.79 239 3894 54.77
21 333 10365 72.11 209 4103 57.71
22 344 10709 74.50 206 4309 60.60
23 309 11018 76.65 208 4517 63.53
24 236 11254 78.29 190 4707 66.20
25 270 11524 80.17 233 4940 69.48
26 248 11772 81.90 154 5094 71.65
27 186 11958 83.19 134 5228 73.53
28 198 12156 84.57 132 5360 75.39
29 180 12336 85.82 124 5484 77.13
30 160 12496 86.93 126 5610 78.90
31 155 12651 88.01 118 5728 80.56
32 145 12796 89.02 103 5831 82.01
33 135 12931 89.96 90 5921 83.28
34 107 13038 90.71 59 5980 84.11
35 116 13154 91.51 72 6052 85.12
36 110 13264 92.28 90 6142 86.39
37 90 13354 92.90 62 6204 87.26
38 79 13433 93.45 52 6256 87.99
39 68 13501 93.93 46 6302 88.64
40 62 13563 94.36 44 6346 89.25
41 41 13604 94.64 43 6389 89.86
42 58 13662 95.05 37 6426 90.38
43 54 13716 95.42 34 6460 90.86
44 43 13759 95.72 29 6489 91.27
45 47 13806 96.05 29 6518 91.67
46 41 13847 96.33 28 6546 92.07
47 33 13880 96.56 27 6573 92.45
48 31 13911 96.78 20 6593 92.73
49 45 13956 97.09 33 6626 93.19
50 31 13987 97.31 21 6647 93.49
51 33 14020 97.54 26 6673 93.85
52 27 14047 97.73 23 6696 94.18
53 15 14062 97.83 19 6715 94.44
54 26 14088 98.01 25 6740 94.80
55 31 14119 98.23 19 6759 95.06
56 25 14144 98.40 21 6780 95.36
57 17 14161 98.52 21 6801 95.65
58 15 14176 98.62 21 6822 95.95
59 9 14185 98.69 8 6830 96.06
60 17 14202 98.80 15 6845 96.27
61 5 14207 98.84 27 6872 96.65
62 17 14224 98.96 15 6887 96.86
63 19 14243 99.09 12 6899 97.03
64 13 14256 99.18 8 6907 97.14
65 10 14266 99.25 8 6915 97.26
66 26 14292 99.43 10 6925 97.40
67 1 14293 99.44 2 6927 97.43
68 6 14299 99.48 9 6936 97.55
69 7 14306 99.53 8 6944 97.67
70 6 14312 99.57 6 6950 97.75
71 7 14319 99.62 10 6960 97.89
72 9 14328 99.68 2 6962 97.92
73 5 14333 99.71 6 6968 98.00
74 2 14335 99.73 10 6978 98.14
75 1 14336 99.74 7 6985 98.24
76 1 14337 99.74 2 6987 98.27
77 4 14341 99.77 8 6995 98.38
78 1 14342 99.78 6 7001 98.47
79 1 14343 99.78 7 7008 98.57
80 0 14343 99.78 3 7011 98.61
81 0 14343 99.78 2 7013 98.64
82 0 14343 99.78 4 7017 98.69
83 0 14343 99.78 6 7023 98.78
84 2 14345 99.80 3 7026 98.82
85 0 14345 99.80 2 7028 98.85
86 1 14346 99.81 3 7031 98.89
87 0 14346 99.81 6 7037 98.97
88 2 14348 99.82 2 7039 99.00
89 1 14349 99.83 6 7045 99.09
90 1 14350 99.83 2 7047 99.11
91 3 14353 99..85 2 7049 99.14
92 0 14353 99.85 1 7050 99.16
93 0 14353 99.85 2 7052 99.18
94 0 14353 99.85 0 7052 99.18
95 0 14353 99.85 1 7053 99.20
96 5 14358 99.89 1 7054 99.21
97 0 14358 99.89 0 7054 99.21
98 0 14358 99.89 1 7055 99.23
99 4 14362 99.92 3 7058 99.27
100 3 14365 99.94 1 7059 100
100-252 9 14374 100 51 7110 100
TOTAL 14374 14374 100 7110 7110 100

More than one-quarter of journal citations are 8 years old or less. Fifty percent of journal citations are 14 years old or less. About 75 percent are 22 years old or less.

More than one quarter of book citations are 11 years old or less, slightly over half are 19 years old or less, and. Seventy five percent are 28 years old or less.

Age Distribution of Book and Journal Citations

The Kolmogorov-Smirnov (K-S) test was used to test the exponentiality of the distribution. The Observed (F(x)) and Estimated (E(x)) cumulative percentages and the absolute differences between the observed and estimated cumulative percentages were calculated.

[D N = [1F(x)-E(x)1] are calculated and are shown in Figures 1 and 2.

Under the assumption that the data follow a negative exponential distribution, the estimated cumulative percentages are calculated using the formula of exponential distribution

E(X) =1-e d x

Where d =1/mean and X = 0, 1, 2, 3… n

Significance at 0.01 levels: The K-S statistic (the critical value of D) is equal to 1.63/n 0.5. In this case n= 252 and hence the critical value of D from table it is observed that the maximum value of D does not exceed this critical value (0.0129) and hence it confirms statistically that the age distribution of citations in both bibliographic forms viz., journals and books, follows a negative exponential distribution in all the fields under study.

Half-Life of Journal Citations

A graph is plotted taking the age of citations (in years) on X-axis and cumulative percentage of citations on Y-axis to find out half-life of citations. A line parallel to the X-axis is drawn from a point say "A" representing the half of the citations to meet the curve say "B". Then perpendicular to X-axis (BC) is drawn from point B to meet the X-axis at C. "C" represents the half-life period of citations.

The half-life value obtained by Brown (1980) for chemical Literature is 9.3 years. Vimala (1997) obtained a half-life value of 16.22 years for biological sciences. Aruna Prasad Reddy (1999) obtained a half-life value of 17.84 years for chemistry and Mahapatra and Bhagavan Das (2000) obtained a half-life value of 17 years for geography. In general literature relating to descriptive aspects like properties of matter, basic methodology etc., basic laws and basic concepts decline more slowly compared to empirical matter. The above figures indicate that the obsolescence rate differs from one subject to another and also from one bibliographic form to another one. It is noticed that the half-life period is longer for books than for journals.

Figure 1. Citation frequency of journals in psychology

Figure 2. Citation frequency of books in psychology

Findings and Conclusion

  1. Nearly 27 percent of journal citations are 8 years old or less, 50 percent are 14 years old or less, and 75 percent are 22 years old or less.
  2. Twenty-seven percent of book citations are 11 years old or less. Fifty-one percent are 19 years old or less. Seventy-five percent are 28 years old or less.
  3. The results of K-S test confirmed statistically that the obsolescence (distribution) rate of journal and book citations follows a negative exponential distribution.
  4. Half-life of journal citations in psychology is 14 years, while it is 19 years for book citations.
  5. Psychology researchers prefer to refer to current journals.
  6. There is a significant difference between the obsolescence of psychology journals and books.

Obsolescence studies play a vital role for librarians, researchers, and information managers as a decision support tool for the retention of the most frequently-used literature, and is also useful for weeding out unused or less-used literature.

References

HOOKER (R H). A study of scientific periodicals. Rev Scient Instrum. 6; 1935; 333-338.

BRODUS (R N).The research literature of the field of speech. Chicago, ACRL (ACRL monograph no.7) 1953.

LOWLER (E). Physiology of the scientists: Age and authorship of citations in selected physiological journals. Physiological Reports. 13; 1963; 537.

LIN (N) and NELSON (C E). Bibliographic reference pattern in core Sociological journals, 1965-66. American Sociology. 4; 1969; 47-50.

HEINZKILL (J R). Characteristics of references in selected scholarly English literature journals. Library Quarterly. 50; 1980; 352-365.

LINE (M B), etc. Pattern of citations to articles with journals: A preliminary test of scatter, concentration and obsolescence. 1972. Bath, Bath University Library.

BROWN (P). The half-life of the chemical literature. Journal of the American Society for Information Science. 31; 1980; 61-65.

VIMALA (V). Bibliometric study of citations in PhD theses in Biological Sciences. Tirupati. S. V. University, PhD. 1997 (Unpublished).

ARUNA PRASAD REDDY (C). Bibliometric study of citations in PhD theses in Chemistry 1964-1997 accepted by Sri Venkateswara University, Tirupati. Visakhapattanam. Andhra University, Ph.1999 (Unpublished).

MAHAPATRA (M) and BHAGAVAN DAS. Impact of research collaboration on growth of literature in Geology: A bibliometric study. SRELS Journal of Information Management. 37; 2000; 95-105.

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