- Email: [email protected]
Rasmussen number greater than one
Applied Ergonomics xxx (2016) 1e6
Contents lists available at ScienceDirect
Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo
Rasmussen number greater than one Robert L. Wears a, b a b
Department of Emergency Medicine, University of Florida, Jacksonville, FL, USA Clinical Safety Research Unit, Imperial College London, London, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 March 2015 Accepted 25 January 2016 Available online xxx
This essay describes the ramifying influence of Jens Rasmussen, illustrating how his work lives on through people whom he has influenced, even though they may have never directly collaborated. I approach this in three ways: a social network analysis of the ‘Rasmussen number’ (an analogue of the € s number); and two citations network analyses based on different search domains and different Erdo network structures. © 2016 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Keywords: Social networks Citation networks
1. Introduction One way to gauge the influence and legacy of a thought leader is to examine his or her influence on others working in the same or related fields by an examination of their citations of the leader's €s was an influential mathematician in work. For example, Paul Erdo the 20th century whose output of published papers was enormous. €s number” to Mathematicians developed the notion of an “Erdo describe the “collaborative distance” between a given person and € s. In this essay I use an analogue e the “Rasmussen number” e Erdo to describe the influence of Jens Rasmussen, and to illustrate how his work lives on through people whom he has influenced, even though they may have never directly collaborated. I approach this in three ways: a social network analysis of the Rasmussen number; a citations network analysis; and my personal reflections of Rasmussen's strong influence on my own work, despite the lack of direct collaboration or contact with him. 2. Methods and sources I analysed the collection of Rasmussen's works compiled by Henning Boje Andersen (personal communication), and supplemented that with internet searches of Google Scholar and ISI Web of Science. I then analysed the retrieved materials using Web of Science, Harzing's Publish or Perish, Lecy's Citation Network Analysis, and Garfield's HistCite (Garfield, 2014; Harzing, 2015; Lecy, 2014). To the extent possible, I removed possible duplicates (eg, a conference paper or technical report later resulting in a journal paper
E-mail addresses: wears@ufl.edu, [email protected].
with the same co-authors and title); however, I included editors of volumes to which Rasmussen contributed a chapter as collaborators, as I feel that is a legitimate reflection of his influence. Different sources, (eg, Google Scholar vs Web of Science) should be expected to yield different citation numbers and documents. Web of Science indexes only a set of core works, but attempts to compile a comprehensive set of citations in those areas. In contrast, Google Scholar is not limited to a core set of sources, but samples the internet extensively, retrieving potential citations based on Google's page-rank score. Thus, it often includes sources in the popular literature that are not represented in Web of Science, which is limited to academic works. In addition, both Publish or Perish and Citations Network Analysis are limited to probabilistic sampling of Google Scholar's results, although their sampling is also weighted by the page-rank score. Because of these difference, specific numbers of citations, journals and co-authors will differ somewhat by source, but the variety of sources affords a sort of triangulation, and the use of the page-rank score gives some assurance that the most influential papers (ie, most searched-for) are included in these data. I note where the results differ substantively by source and speculate on the reasons for those differences. 3. The Rasmussen number €s number, Jens Rasmussen Following the definition of an Erdo starts the series as the only author with Rasmussen number of 0. Anyone else's Rasmussen number is kþ1, where k is the lowest Rasmussen number of another of his or her co-authors. For example, Richard Cook and Kim Vicente (among others) have Rasmussen numbers of 1 because both have co-authored at least
http://dx.doi.org/10.1016/j.apergo.2016.01.014 0003-6870/© 2016 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
2
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
one publication with Rasmussen (Cook and Rasmussen, 2005; Vicente and Rasmussen, 1992); I have a Rasmussen number of 2, since I have co-authored publications with Cook, but never with Rasmussen (Wears et al., 2006); and so on ad infinitum. 4. Results 4.1. Direct influence Rasmussen's direct output is remarkable for its solitary nature, making his broader influence perhaps even more surprising (see Fig. 1). Of 324 works (papers, chapters, books, reports) from 1955 to 2005 in Andersen's compilation, almost 2/3 s (193) were produced by Rasmussen alone; 131 had 1 co-author, 51 had 2, 15 had 3, 7 had 4, and 1 had 5 co-authors. There were a total of 97 different coauthors; the majority of these had only a single co-authored publication with Rasmussen. Thus I estimate that there are 97 direct collaborators who have Rasmussen number equal to 1, a class that is now sadly closed to new entrants. Six collaborators (Vicente, Pjetersen, Goodstein, Le Plat, Pedersen, and Brehmer) were the most common co-authors, collectively participating in just over 50% of the co-authored publications. 4.2. Indirect influence (legacy)
0
20
Frequency 40
60
80
Although the class of authors with Rasmussen number equal to 1 is small, the numbers grow exponentially for Rasmussen number greater than 1. Thus, a fuller understanding of Rasmussen's influence might be gained from an analysis of the works he did not author, but which cite one or more of his works. Using Google scholar and limiting to the 1000 works with the highest page-rank, after eliminating papers from authors with similar names based on their titles (eg, Udder health in automatically milked cows), and merging potential duplicates, I identified 146 works with a least one citation, for a total of 17,226 citations; roughly half of these were to books, chapters, or reports, so I will use the general term “works” to cover these efforts in addition to traditional academic papers. The number of citations has grown steadily over time, reaching 100 cites per year in 2000 and continuing to grow thereafter (see Fig. 2). Of the academic papers, 28 journals cited Rasmussen over 100 times (see Table 1). The majority of these journals were in the field of human factors and ergonomics, but the range of fields is quite broad, whether considering the sciences, such as ergonomics,
0
5
Number of papers
10
Fig. 1. Distribution of Rasmussen's co-authors.
15
psychology, computer science and informatics, organizational behaviour, and control engineering; or the domains of application, such as healthcare, aviation, nuclear power, management, and business. This wide range of interests is remarkable when one considers that Rasmussen was fundamentally an engineer without a background in these fields, and that he worked primarily in a relatively narrow domain of application (operator performance in nuclear power plants). This breadth of interest and influence speaks to his ability to do three things: to engage deeply and intimately with real work in a specific context; to abstract from that engagement principles of human and system behaviour that are broadly generalizable; and to communicate those principles in a way easily grasped by readers outside his own sphere of work. The distribution of citations is strongly skewed to the right (see Fig. 3): there were 50 works with 50 citations or more (ie, an hindex of 50); four works had over 1000 citations, 2 books on cognitive engineering (Rasmussen, 1986; Rasmussen et al., 1994), and 2 papers: “Skills, rules and knowledge” (Rasmussen, 1983), and “Risk management in a dynamic society” (Rasmussen, 1997). However, we noted a substantial difference between Google Scholar and Web of Science in one respect; Google Scholar reported 3009 citations to Information Processing and Human-Machine Interaction, while Web of Science reported only 11 citations from their Core Collections. The majority of these citations were from a web source (citeulike.org), so their provenance is uncertain, but it seems likely they reflect sources in the popular or grey literature not included in Web of Science's more formal core collections. 4.3. Network influence (legacy) To further explore Rasmussen's legacy, I analysed citation networks from the two most frequently cited papers noted above: “Risk management” (RM) and “Skills, rules, and knowledge” (SRK). I did this separately for our two primary sources (Web of Science and Google Scholar); each lent itself to a slightly different analysis. 4.3.1. Web of science I used Garfield's HistCite to trace the influence of Rasmussen's work over time, using these two papers as seeds. Web of Science reports 859 direct citations by 1791 authors in 313 journals and 44 countries, and a total of 12,050 citations from all sources. Fig. 4 plots influence of these two papers as a historiograph; a representation of the flow of citations over the years, using only citing papers that themselves have at least 50 citations (and thus arguably represent the pathway of greatest influence). One can see that there is remarkably little overlap in the citation ‘descendants’ from these two papers; only one highly referenced paper (Vicente and Rasmussen, 1992) is on the path between SRK and RM, and none of these influential papers cites both. Although citing papers refer to only one of the two works, the distribution of fields among the two branches seems remarkably similar, heavily oriented towards human factors and safety science, but with a reasonable representation of papers from organizational behaviour, computer science, and healthcare. 4.3.2. Google scholar Because citations networks tend to explode combinatorially, I used 3% snowball sampling for 3 citation levels to make the search computationally reasonable and to avoid being shut out from Google Scholar due to overuse. Google Scholar additionally limited the search to the top 1000 papers by page-rank score, so by choosing a lower sampling proportion I could be surer of including more papers in the 2nd and 3rd generations. Probabilistic snowball sampling has huge efficiency advantages and has been shown to perform reasonably well, typically retrieving roughly 70e80% of
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
3
Fig. 2. Annual growth in citations.
Table 1 Most highly citing journals (Web of Science). Journal
Number of citations
Safety Sciencea IEEE Transactions on Systems, Man & Cyberneticsb Human Factors Ergonomics Journal of the American Medical Informatics Association Reliability Engineering & Safety Science Journal of Biomedical Informatics International Journal of Man-Machine Studies
2025 1506 1196 1090 531 457 445 438
a b
Formerly Journal of Occupational Accidents. Now IEEE Trans on SMC, Part A.
Fig. 3. Distribution of citations per Rasmussen paper, book, or report.
important papers in a citations network (Lecy and Beatty, 2012). It does, however, have a potential limitation in that it is possible to get trapped in a local, niche area. Because the preceding analysis
showed the two papers tended to be used separately, I have handled them separately here. The nature of citing journals differed dramatically between RM and SRK in this dataset. Nine of the ten top citing journals for SRK were in healthcare, compared to only three of ten for RM (see Fig. 5). This difference likely reflects differences in the two sampling schemes, and also differences in citation practices between fields; healthcare is known to produce larger numbers of smaller papers, and thus to be over-represented in citation counts involving multiple domains. Using Citation Network Analysis, I plotted citation networks for each paper and identified groups of closely related papers using a community detection algorithm in the CNA package for R (Hornik, 2015; Lecy, 2014). The network for RM showed at least 5 major groups (see Fig. 6). Three groups were highly interconnected, and had rather complex inner structures: a cluster of papers focused on cognitive work analysis and naturalistic decision-making; a cluster focused on engineered approaches to human factors (labelled ‘safety-I’ after Hollnagel (2014)); and a third focused on adaptive approaches to human factors (labelled ‘safety-II). Two other clusters had only sparse connections to the rest of the network and simple, highly centralized inner structures: a cluster focused on organizational behaviour and management; and a cluster in the popular literature initiated by Thaler and Sunstein's Nudge (2009). The network for SRK has a quite different structure (see Fig. 7), with only 3 major groups which are only sparsely connected to one another. Interesting, two groups (medical informatics and healthcare) both deal with different but related aspects of the healthcare domain (information technology; and quality and safety) but are only tenuously connected to each other. The third group, a general human factors and safety cluster, is distantly connected to healthcare but not to medical informatics e somewhat surprising since a major rationale for the introduction of information technology into healthcare is ostensibly to improve quality and safety. 5. Discussion Jens Rasmussen worked most of his life in a narrow domain
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
4
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
Fig. 4. Historiograph showing the flow of citations from RM and SRK. The y-axis represents time (moving downwards moves forward in time). The size of a node is proportional to the number of citations. Arrows show the direction of influence (ie, from the cited to the citing paper).
(nuclear power) in a small country (Denmark); the majority of his
works were not collaborative, but rather singly-authored. In
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
5
Fig. 5. Top citing journals for RM and SRK.
Fig. 6. Citations network for RM, showing major groups.
Fig. 7. Citations network for SRK, showing major groups.
addition, in working for the National Laboratory as Risø he was not expected to produce peer-reviewed publications, so his published output was largely in the form of technical reports, books, and book chapters, with just a smattering of academic papers appeared primarily in the safety engineering literature. Given these conditions, the extent of his influence is remarkable, spanning multiple countries, scientific disciplines, and application domains. He had less than 100 direct collaborators as co-authors; thus, the bulk of his legacy is found in secondary readers of his work, no doubt influenced by the select class of authors whose Rasmussen number is equal to one. This was my personal history e introduced to Rasmussen's work (I believe RM was the first) by two mentorcolleagues (Richard Cook and David Woods), both having Rasmussen numbers of 1. The degree to which Rasmussen's work has resonated with researchers in different countries, domains, scientific disciplines, and languages testifies to his ability to distill the essence of complex phenomena in generalized, compact, and meaningful ways, without losing any of their essential complexity. This capability has made his work directly applicable to domains he doubtless never envisioned (eg, an American emergency department (Wears et al., 2008)). Vicente has remarked that it is hard to think of any other line of work that has had such an extensive influence on theory and practice in industry, psychology, and cognitive science (Vicente, 1997). In the course of performing this analysis, I had the opportunity to sift through many of Rasmussen's works that I have come to rely on, and to examine many others that I had not previously seen. This made it becomes easier for me to understand how his influence became so extensive, as the titles and subject matter of many older works seem just as relevant and applicable today as they were when they were written e perhaps even more so. Our safety and performance problems are not getting any simpler; thus we should hope that his legacy and influence continue to grow.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
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References Cook, R.I., Rasmussen, J., 2005. “Going solid”: a model of system dynamics and consequences for patient safety. Qual. Saf. Health Care 14 (2), 130e134. Garfield, E., 2014, August 2014. Eugene Garfield. Retrieved 24 March 2015, from. http://www.garfield.library.upenn.edu/. Harzing, A.-W., 2015. Publish or Persish. Retrieved 24 March 2015, from. http:// www.harzing.com/pop.htm. Hollnagel, E., 2014. Safety-i and Safety-ii: the Past and Future of Safety Management. Ashgate, Farnham, UK. Hornik, K., 2015, 4 March 2015. R FAQ. Retrieved 27 March 2015, from. http://CRAN. R-project.org/doc/FAQ/R-FAQ.html. Lecy, J.D., 2014. Citation Network Analysis. Retrieved 24 March 2015, from. http:// lecy.info/resources/CNA%20Overview.pdf. Lecy, J.D., Beatty, K.E., 2012. Representative literature reviews using constrained snowball sampling and citation network analysis. SSRN Electron. J. Retrieved from http://ssrn.com/abstract¼1992601. Rasmussen, J., 1983. Skills, rules and knowledge; signals, signs and symbols and other distinctions in human performance models. IEEE Trans. Syst. Man Cybern. 13 (3), 257e266.
Rasmussen, J., 1986. Information Processing and Human-machine Interaction: an Approach to Cognitive Engineering (Amsterdam: North Holland). Rasmussen, J., 1997. Risk management in a dynamic society: a modeling problem. Saf. Sci. 27 (2/3), 183e213. Rasmussen, J., Pejtersen, A.M., Goodstein, L.P., 1994. Cognitive Systems Engineering. John Wiley & Sons, Inc, New York. Thaler, R., Susstein, C.R., 2009. Nudge: Improving Decisions about Health, Wealth, and Happiness. Penguin Books, London, UK. Vicente, K.J., 1997. A history of cognitive engineering research at Risø (1962e1979). Proc. Hum. Factors Ergon. Soc. Annu. Meet. 41 (1), 210e214. http://dx.doi.org/ 10.1177/107118139704100148. Vicente, K.J., Rasmussen, J., 1992. Ecological interface design: theoretical foundations. Syst. Man Cybern. … 22 (4), 589e606. Wears, R.L., Cook, R.I., Perry, S.J., 2006. Automation, interaction, complexity, and failure: a case study. Reliab. Eng. Syst. Saf. 91 (12), 1494e1501. http://dx.doi.org/ 10.1016/j.ress.2006.01.009. Wears, R.L., Perry, S.J., Anders, S., Woods, D.D., 2008. Resilience in the emergency department. In: Hollnagel, E., Nemeth, C.P., Dekker, S.W.A. (Eds.), Resilience Engineering: Remaining Sensitive to the Possibility of Failure. Ashgate, Aldershot, UK, pp. 193e210.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
Contents lists available at ScienceDirect
Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo
Rasmussen number greater than one Robert L. Wears a, b a b
Department of Emergency Medicine, University of Florida, Jacksonville, FL, USA Clinical Safety Research Unit, Imperial College London, London, UK
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 March 2015 Accepted 25 January 2016 Available online xxx
This essay describes the ramifying influence of Jens Rasmussen, illustrating how his work lives on through people whom he has influenced, even though they may have never directly collaborated. I approach this in three ways: a social network analysis of the ‘Rasmussen number’ (an analogue of the € s number); and two citations network analyses based on different search domains and different Erdo network structures. © 2016 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Keywords: Social networks Citation networks
1. Introduction One way to gauge the influence and legacy of a thought leader is to examine his or her influence on others working in the same or related fields by an examination of their citations of the leader's €s was an influential mathematician in work. For example, Paul Erdo the 20th century whose output of published papers was enormous. €s number” to Mathematicians developed the notion of an “Erdo describe the “collaborative distance” between a given person and € s. In this essay I use an analogue e the “Rasmussen number” e Erdo to describe the influence of Jens Rasmussen, and to illustrate how his work lives on through people whom he has influenced, even though they may have never directly collaborated. I approach this in three ways: a social network analysis of the Rasmussen number; a citations network analysis; and my personal reflections of Rasmussen's strong influence on my own work, despite the lack of direct collaboration or contact with him. 2. Methods and sources I analysed the collection of Rasmussen's works compiled by Henning Boje Andersen (personal communication), and supplemented that with internet searches of Google Scholar and ISI Web of Science. I then analysed the retrieved materials using Web of Science, Harzing's Publish or Perish, Lecy's Citation Network Analysis, and Garfield's HistCite (Garfield, 2014; Harzing, 2015; Lecy, 2014). To the extent possible, I removed possible duplicates (eg, a conference paper or technical report later resulting in a journal paper
E-mail addresses: wears@ufl.edu, [email protected].
with the same co-authors and title); however, I included editors of volumes to which Rasmussen contributed a chapter as collaborators, as I feel that is a legitimate reflection of his influence. Different sources, (eg, Google Scholar vs Web of Science) should be expected to yield different citation numbers and documents. Web of Science indexes only a set of core works, but attempts to compile a comprehensive set of citations in those areas. In contrast, Google Scholar is not limited to a core set of sources, but samples the internet extensively, retrieving potential citations based on Google's page-rank score. Thus, it often includes sources in the popular literature that are not represented in Web of Science, which is limited to academic works. In addition, both Publish or Perish and Citations Network Analysis are limited to probabilistic sampling of Google Scholar's results, although their sampling is also weighted by the page-rank score. Because of these difference, specific numbers of citations, journals and co-authors will differ somewhat by source, but the variety of sources affords a sort of triangulation, and the use of the page-rank score gives some assurance that the most influential papers (ie, most searched-for) are included in these data. I note where the results differ substantively by source and speculate on the reasons for those differences. 3. The Rasmussen number €s number, Jens Rasmussen Following the definition of an Erdo starts the series as the only author with Rasmussen number of 0. Anyone else's Rasmussen number is kþ1, where k is the lowest Rasmussen number of another of his or her co-authors. For example, Richard Cook and Kim Vicente (among others) have Rasmussen numbers of 1 because both have co-authored at least
http://dx.doi.org/10.1016/j.apergo.2016.01.014 0003-6870/© 2016 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
2
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
one publication with Rasmussen (Cook and Rasmussen, 2005; Vicente and Rasmussen, 1992); I have a Rasmussen number of 2, since I have co-authored publications with Cook, but never with Rasmussen (Wears et al., 2006); and so on ad infinitum. 4. Results 4.1. Direct influence Rasmussen's direct output is remarkable for its solitary nature, making his broader influence perhaps even more surprising (see Fig. 1). Of 324 works (papers, chapters, books, reports) from 1955 to 2005 in Andersen's compilation, almost 2/3 s (193) were produced by Rasmussen alone; 131 had 1 co-author, 51 had 2, 15 had 3, 7 had 4, and 1 had 5 co-authors. There were a total of 97 different coauthors; the majority of these had only a single co-authored publication with Rasmussen. Thus I estimate that there are 97 direct collaborators who have Rasmussen number equal to 1, a class that is now sadly closed to new entrants. Six collaborators (Vicente, Pjetersen, Goodstein, Le Plat, Pedersen, and Brehmer) were the most common co-authors, collectively participating in just over 50% of the co-authored publications. 4.2. Indirect influence (legacy)
0
20
Frequency 40
60
80
Although the class of authors with Rasmussen number equal to 1 is small, the numbers grow exponentially for Rasmussen number greater than 1. Thus, a fuller understanding of Rasmussen's influence might be gained from an analysis of the works he did not author, but which cite one or more of his works. Using Google scholar and limiting to the 1000 works with the highest page-rank, after eliminating papers from authors with similar names based on their titles (eg, Udder health in automatically milked cows), and merging potential duplicates, I identified 146 works with a least one citation, for a total of 17,226 citations; roughly half of these were to books, chapters, or reports, so I will use the general term “works” to cover these efforts in addition to traditional academic papers. The number of citations has grown steadily over time, reaching 100 cites per year in 2000 and continuing to grow thereafter (see Fig. 2). Of the academic papers, 28 journals cited Rasmussen over 100 times (see Table 1). The majority of these journals were in the field of human factors and ergonomics, but the range of fields is quite broad, whether considering the sciences, such as ergonomics,
0
5
Number of papers
10
Fig. 1. Distribution of Rasmussen's co-authors.
15
psychology, computer science and informatics, organizational behaviour, and control engineering; or the domains of application, such as healthcare, aviation, nuclear power, management, and business. This wide range of interests is remarkable when one considers that Rasmussen was fundamentally an engineer without a background in these fields, and that he worked primarily in a relatively narrow domain of application (operator performance in nuclear power plants). This breadth of interest and influence speaks to his ability to do three things: to engage deeply and intimately with real work in a specific context; to abstract from that engagement principles of human and system behaviour that are broadly generalizable; and to communicate those principles in a way easily grasped by readers outside his own sphere of work. The distribution of citations is strongly skewed to the right (see Fig. 3): there were 50 works with 50 citations or more (ie, an hindex of 50); four works had over 1000 citations, 2 books on cognitive engineering (Rasmussen, 1986; Rasmussen et al., 1994), and 2 papers: “Skills, rules and knowledge” (Rasmussen, 1983), and “Risk management in a dynamic society” (Rasmussen, 1997). However, we noted a substantial difference between Google Scholar and Web of Science in one respect; Google Scholar reported 3009 citations to Information Processing and Human-Machine Interaction, while Web of Science reported only 11 citations from their Core Collections. The majority of these citations were from a web source (citeulike.org), so their provenance is uncertain, but it seems likely they reflect sources in the popular or grey literature not included in Web of Science's more formal core collections. 4.3. Network influence (legacy) To further explore Rasmussen's legacy, I analysed citation networks from the two most frequently cited papers noted above: “Risk management” (RM) and “Skills, rules, and knowledge” (SRK). I did this separately for our two primary sources (Web of Science and Google Scholar); each lent itself to a slightly different analysis. 4.3.1. Web of science I used Garfield's HistCite to trace the influence of Rasmussen's work over time, using these two papers as seeds. Web of Science reports 859 direct citations by 1791 authors in 313 journals and 44 countries, and a total of 12,050 citations from all sources. Fig. 4 plots influence of these two papers as a historiograph; a representation of the flow of citations over the years, using only citing papers that themselves have at least 50 citations (and thus arguably represent the pathway of greatest influence). One can see that there is remarkably little overlap in the citation ‘descendants’ from these two papers; only one highly referenced paper (Vicente and Rasmussen, 1992) is on the path between SRK and RM, and none of these influential papers cites both. Although citing papers refer to only one of the two works, the distribution of fields among the two branches seems remarkably similar, heavily oriented towards human factors and safety science, but with a reasonable representation of papers from organizational behaviour, computer science, and healthcare. 4.3.2. Google scholar Because citations networks tend to explode combinatorially, I used 3% snowball sampling for 3 citation levels to make the search computationally reasonable and to avoid being shut out from Google Scholar due to overuse. Google Scholar additionally limited the search to the top 1000 papers by page-rank score, so by choosing a lower sampling proportion I could be surer of including more papers in the 2nd and 3rd generations. Probabilistic snowball sampling has huge efficiency advantages and has been shown to perform reasonably well, typically retrieving roughly 70e80% of
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
3
Fig. 2. Annual growth in citations.
Table 1 Most highly citing journals (Web of Science). Journal
Number of citations
Safety Sciencea IEEE Transactions on Systems, Man & Cyberneticsb Human Factors Ergonomics Journal of the American Medical Informatics Association Reliability Engineering & Safety Science Journal of Biomedical Informatics International Journal of Man-Machine Studies
2025 1506 1196 1090 531 457 445 438
a b
Formerly Journal of Occupational Accidents. Now IEEE Trans on SMC, Part A.
Fig. 3. Distribution of citations per Rasmussen paper, book, or report.
important papers in a citations network (Lecy and Beatty, 2012). It does, however, have a potential limitation in that it is possible to get trapped in a local, niche area. Because the preceding analysis
showed the two papers tended to be used separately, I have handled them separately here. The nature of citing journals differed dramatically between RM and SRK in this dataset. Nine of the ten top citing journals for SRK were in healthcare, compared to only three of ten for RM (see Fig. 5). This difference likely reflects differences in the two sampling schemes, and also differences in citation practices between fields; healthcare is known to produce larger numbers of smaller papers, and thus to be over-represented in citation counts involving multiple domains. Using Citation Network Analysis, I plotted citation networks for each paper and identified groups of closely related papers using a community detection algorithm in the CNA package for R (Hornik, 2015; Lecy, 2014). The network for RM showed at least 5 major groups (see Fig. 6). Three groups were highly interconnected, and had rather complex inner structures: a cluster of papers focused on cognitive work analysis and naturalistic decision-making; a cluster focused on engineered approaches to human factors (labelled ‘safety-I’ after Hollnagel (2014)); and a third focused on adaptive approaches to human factors (labelled ‘safety-II). Two other clusters had only sparse connections to the rest of the network and simple, highly centralized inner structures: a cluster focused on organizational behaviour and management; and a cluster in the popular literature initiated by Thaler and Sunstein's Nudge (2009). The network for SRK has a quite different structure (see Fig. 7), with only 3 major groups which are only sparsely connected to one another. Interesting, two groups (medical informatics and healthcare) both deal with different but related aspects of the healthcare domain (information technology; and quality and safety) but are only tenuously connected to each other. The third group, a general human factors and safety cluster, is distantly connected to healthcare but not to medical informatics e somewhat surprising since a major rationale for the introduction of information technology into healthcare is ostensibly to improve quality and safety. 5. Discussion Jens Rasmussen worked most of his life in a narrow domain
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
4
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
Fig. 4. Historiograph showing the flow of citations from RM and SRK. The y-axis represents time (moving downwards moves forward in time). The size of a node is proportional to the number of citations. Arrows show the direction of influence (ie, from the cited to the citing paper).
(nuclear power) in a small country (Denmark); the majority of his
works were not collaborative, but rather singly-authored. In
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
R.L. Wears / Applied Ergonomics xxx (2016) 1e6
5
Fig. 5. Top citing journals for RM and SRK.
Fig. 6. Citations network for RM, showing major groups.
Fig. 7. Citations network for SRK, showing major groups.
addition, in working for the National Laboratory as Risø he was not expected to produce peer-reviewed publications, so his published output was largely in the form of technical reports, books, and book chapters, with just a smattering of academic papers appeared primarily in the safety engineering literature. Given these conditions, the extent of his influence is remarkable, spanning multiple countries, scientific disciplines, and application domains. He had less than 100 direct collaborators as co-authors; thus, the bulk of his legacy is found in secondary readers of his work, no doubt influenced by the select class of authors whose Rasmussen number is equal to one. This was my personal history e introduced to Rasmussen's work (I believe RM was the first) by two mentorcolleagues (Richard Cook and David Woods), both having Rasmussen numbers of 1. The degree to which Rasmussen's work has resonated with researchers in different countries, domains, scientific disciplines, and languages testifies to his ability to distill the essence of complex phenomena in generalized, compact, and meaningful ways, without losing any of their essential complexity. This capability has made his work directly applicable to domains he doubtless never envisioned (eg, an American emergency department (Wears et al., 2008)). Vicente has remarked that it is hard to think of any other line of work that has had such an extensive influence on theory and practice in industry, psychology, and cognitive science (Vicente, 1997). In the course of performing this analysis, I had the opportunity to sift through many of Rasmussen's works that I have come to rely on, and to examine many others that I had not previously seen. This made it becomes easier for me to understand how his influence became so extensive, as the titles and subject matter of many older works seem just as relevant and applicable today as they were when they were written e perhaps even more so. Our safety and performance problems are not getting any simpler; thus we should hope that his legacy and influence continue to grow.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014
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References Cook, R.I., Rasmussen, J., 2005. “Going solid”: a model of system dynamics and consequences for patient safety. Qual. Saf. Health Care 14 (2), 130e134. Garfield, E., 2014, August 2014. Eugene Garfield. Retrieved 24 March 2015, from. http://www.garfield.library.upenn.edu/. Harzing, A.-W., 2015. Publish or Persish. Retrieved 24 March 2015, from. http:// www.harzing.com/pop.htm. Hollnagel, E., 2014. Safety-i and Safety-ii: the Past and Future of Safety Management. Ashgate, Farnham, UK. Hornik, K., 2015, 4 March 2015. R FAQ. Retrieved 27 March 2015, from. http://CRAN. R-project.org/doc/FAQ/R-FAQ.html. Lecy, J.D., 2014. Citation Network Analysis. Retrieved 24 March 2015, from. http:// lecy.info/resources/CNA%20Overview.pdf. Lecy, J.D., Beatty, K.E., 2012. Representative literature reviews using constrained snowball sampling and citation network analysis. SSRN Electron. J. Retrieved from http://ssrn.com/abstract¼1992601. Rasmussen, J., 1983. Skills, rules and knowledge; signals, signs and symbols and other distinctions in human performance models. IEEE Trans. Syst. Man Cybern. 13 (3), 257e266.
Rasmussen, J., 1986. Information Processing and Human-machine Interaction: an Approach to Cognitive Engineering (Amsterdam: North Holland). Rasmussen, J., 1997. Risk management in a dynamic society: a modeling problem. Saf. Sci. 27 (2/3), 183e213. Rasmussen, J., Pejtersen, A.M., Goodstein, L.P., 1994. Cognitive Systems Engineering. John Wiley & Sons, Inc, New York. Thaler, R., Susstein, C.R., 2009. Nudge: Improving Decisions about Health, Wealth, and Happiness. Penguin Books, London, UK. Vicente, K.J., 1997. A history of cognitive engineering research at Risø (1962e1979). Proc. Hum. Factors Ergon. Soc. Annu. Meet. 41 (1), 210e214. http://dx.doi.org/ 10.1177/107118139704100148. Vicente, K.J., Rasmussen, J., 1992. Ecological interface design: theoretical foundations. Syst. Man Cybern. … 22 (4), 589e606. Wears, R.L., Cook, R.I., Perry, S.J., 2006. Automation, interaction, complexity, and failure: a case study. Reliab. Eng. Syst. Saf. 91 (12), 1494e1501. http://dx.doi.org/ 10.1016/j.ress.2006.01.009. Wears, R.L., Perry, S.J., Anders, S., Woods, D.D., 2008. Resilience in the emergency department. In: Hollnagel, E., Nemeth, C.P., Dekker, S.W.A. (Eds.), Resilience Engineering: Remaining Sensitive to the Possibility of Failure. Ashgate, Aldershot, UK, pp. 193e210.
Please cite this article in press as: Wears, R.L., Rasmussen number greater than one, Applied Ergonomics (2016), http://dx.doi.org/10.1016/ j.apergo.2016.01.014