Karl Ulrich Smith
Karl Ulrich Smith (1907–1994) - K.U. to friends and colleagues - was born in Zanesville, Ohio. His pivotal contributions to ergonomic/ human factors (E/HF) science have been recognized by the 1994 Founders Award from the International Ergonomics Association (IEA), the 1986 Paul M. Fitts Award from the US Human Factors and Ergonomics Society (HFES) for outstanding contributions to the education and training of human factors specialists, and establishment in 1997 of the IEA Student Award in his name. He has summarized his role in the development of the field with two publications (Smith 1987; 1988). A more recent publication summarizes his contributions to the emergence of E/HF science and the establishment of the IEA (Smith and Smith 2000).
K.U.’s professional career comprised three periods, his prewar graduate and postgraduate years, his service as a civilian scientist in the military during World War II (WWII), and the balance of his career at the University of Wisconsin (UW) in Madison.
K.U. attended the Ohio University in Athens and Miami University of Ohio in Oxford as an undergraduate, receiving his BA in psychology from the latter in 1931. He then moved on to the graduate program in psychology at Brown University, receiving his MA in 1933 and PhD in 1935. K.U. then moved to the University of Rochester, where he assumed responsibility for upgrading the teaching, laboratory facilities, and research program in experimental psychology. K.U. was always proud of future distinguished psychologists who had taken his courses at Rochester, among them Charles Bridgman, Paul Fitts, William Kappauf, Karl Kryter, J.C.R. Licklider, Leonard Mead, and Clifford Morgan. On accepting the HFES Fitts Award in 1986, K.U. opened his remarks by noting, “Paul Fitts was my student.” K.U.’s own research at both Brown and Rochester dealt with vision, audition, and learning and their neurological control in both animal and human subjects.
K.U. was a prodigious writer, authoring 15 textbooks and monographs, and some 165 scientific reports, 120 book chapters and proceedings or technical reports, and 11 research films. Margaret, his wife, played a crucial professional role in reviewing, editing, and reworking many of these writings, and served as coauthor on two major texts (Smith and Smith 1966; 1973).
With the onset of WWII, the US military faced the dual challenge of training many thousands of combat personnel, plus developing and adapting designs of new equipment and operations to fit their needs, thus providing the impetus for development of E/HF science in the US (Smith 1987). In 1943, K.U. joined a group of some 20 psychologists as assistant research director of a radar operator training project at Camp Murphy, Hobe Sound, Florida. A year later he was asked to direct his own project at the School for Flexible Gunnery in Laredo, Texas. K.U.’s key E/HF contributions with the Florida project included one of the first comprehensive behavioral analyses of perceptual performance, and documentation of perceptual fatigue in radar operators. The latter finding anticipated by some three to four decades observations of visual complaints among VDT workers. His analysis of performance problems with feedback delay in servocontrolled gunnery tracking systems represents one of the first systematic studies of the effects of delayed machine feedback on tracking, and stimulated a lifelong interest in performance effects of perturbed sensory feedback that led to development of the field of behavioral cybernetics.
The postwar period saw full flowering of K.U.’s career as an E/HF teacher, researcher, practitioner, and innovator. Spent entirely at UW-Madison, it was broadly concerned with extending wartime research on fitting military equipment to the combat soldier to fitting the job to the worker. In 1947 he joined the faculty of the UW Department of Psychology, ultimately achieving rank of full professor. His research and teaching over the next 30 years focused on E/HF problems, features of human development and aging, and many facets of the human perceptual-motor behavior.
K.U.’s key contributions to E/HF at Wisconsin encompass theoretical, empirical, applied, and teaching influences (see next section), helping to found the IEA (Smith 1988), and originating the field of behavioral cybernetics (Smith 1962, 1972; Smith and Smith 1962, 1966). From 1956 to 1959, the Human Factors Section of the European Productivity Agency (EPA) mounted Project 335 to assess how E/HF might benefit postwar recovery in Europe. The project evaluated E/HF programs in the US and identified K.U.’s laboratory as the only US university installation carrying out nonmilitary research on E/HF issues with work design. As a result, he was invited to attend a seminar on “Fitting the job to the worker” at the University of Leiden in Holland in 1957, which adopted a set of proposals drafted by K.U. to establish an international association of work scientists. He subsequently served as a member of a steering committee set up to implement this plan, and served as the first treasurer of the International Association of Ergonomic Scientists, formally organized at a 1958 meeting in Paris, and renamed the IEA at a meeting in Zurich in 1959. K.U.’s wartime observations of the dramatically negative effects of feedback delay on tracking performance (Smith 1962) inspired his conceptualization of behavior as a closed-loop or cybernetic feedback- and feedforward controlled process, and prompted formulation of an allinclusive theory of behavioral organization termed behavioral cybernetics (Smith and Smith 1962, 1966, 1973; Smith 1972). In the early 1960s he established the Behavioral Cybernetics Laboratory at UW, one of the first in the country to use real-time, computer-controlled techniques, coupled with closed-circuit television methods, for research on the self-regulation of behavioral and physiological functions, emphasizing visual control of motion with delayed and spatially displaced visual feedback (Smith 1962; Smith and Smith 1962).
3 INFLUENCES ON E/HF
K.U.’s diverse conceptual, empirical, applied, and teaching innovations and contributions in the E/HF field were all grounded in a fundamental concern with human work viewed as a behavioral cybernetic process.
One of K.U.’s lasting impacts will rest on the scope and innovativeness of his theoretical ideas, set forth in an extensive body of books and papers. First and foremost, he was a student of human work. He considered work, organized and expressed through our behavior and performance and strongly affected by feedback, to be the engine of human civilization and the human condition, manifest in our life span development and growth, our social and societal relationships, our commerce and culture, our organizations and institutions, our national and ethnic identities, indeed, our origins and emergence in evolution. He advocated a work theory of economic behavior in contrast to classical economic concepts. He conceived of human technological evolution as a self-selective process, mediated through work. More broadly, he conceived and developed a general theory of biological evolution as a self- controlled, behavioral cybernetic process controlled through feedback selection, in contrast to Darwinian dogma of environmental selection.
K.U.’s interpretation of human performance in work was grounded in behavioral cybernetic theory, which assumed a closed-loop coupling of work design and variability in work performance (Smith 1965). As far as he was concerned, any process or operation involving human performance must be understood from a E/HF perspective. To K.U., human factoring the design of tools, equipment, jobs, work teams, organizations, or institutions meant that the design attributes of these different features of the work environment generated modalities of sensory feedback that could be effectively controlled, in a closed-loop fashion, by the behavioral performance of the worker.
These concepts motivated his application of behaviora cybernetic principles of work design in diverse contexts, including instrumental performance with tools and machines, learning, occupational health, safety and hazard management, rehabilitation, and social cybernetics (the study of social and group behavior as a feedback-controlled process). The scientific and/or practical significance of his ideas typically were well ahead of the rest of the E/HF field. For example, the scope and power of social cybernetic theory in accounting for how interpersonal performance in different team, group, organizational or institutional contexts may be influenced by different social design and social feedback factors (Smith 1974) remains unmatched by any other social psychological theory. His seminal paper on E/HF principles of rehabilitation (Smith and Henry 1967) anticipated many rehabilitative systems design concerns addressed by the Americans With Disabilities Act some two decades later. His application of cybernetic concepts to the organizational design of workplace health and safety programs (Smith 1979), based on worker participation in hazard detection and evaluation plus safety decision-making, originated the field of hazard management and has yielded demonstrable occupational safety benefits. His theory of learning as a behavioral cybernetic process influenced principally by educational design factors (Smith and Smith 1958, 1966) is amply supported by a large body of empirical evidence, but has yet to be generally accepted.
K.U. invented many new methodologies and applied new technologies to E/HF research. He made experimental participants part of closed electronic circuits to time their component motions of gait, writing, and other complex motor performances. He and his brother pioneered closed-circuit video techniques to delay and spatially displace visual feedback. He innovated research involving stereoscopic television, audiovisual teaching machines, human-computer closed-loop methods, psychopharmacological methods, and historical studies of human work through audiotape recordings of people’s recollections. In originating and elaborating the field of behavioral cybernetics, K.U. and his students compiled a body of experimental findings on the behavioral and physiological effects of delayed and spatially displaced sensory feedback that still stands as the most extensive in the literature (Smith 1962; 1972; Smith and Smith 1962). His extension of behavioral cybernetic research to the study of social cybernetics generated a body of experimental findings on effects of different social feedback factors on different modes of social tracking performance that has yet to be duplicated. His research also explored performance effects of incorporating E/HF design in many other new and diverse areas, including work organization, rehabilitation, education and learning, community development, athletics, testing, and human–machine interaction. Although such applications of E/HF research are widely accepted today, many were groundbreaking at the time.
Applied E/HF Contributions.
At UW, K.U. operated from the psychology department but loudly believed (he did nothing quietly) in breaking the boundaries of traditional E/HF and psychological research. He continually invented and pioneered applied interdisciplinary research. He was involved in establishing new university departments in industrial psychology, industrial relations, and psychopharmacology. Many of his projects rested upon the behavioral cybernetic premise that those affected by the slings and arrows of societal misfortune should play a direct participatory role in rehabilitation or risk abatement efforts. The International Center for Community Ergonomics at UW represents one of the direct outgrowths of these early projects.
Another of K.U.’s applied E/HF causes was the use and misuse of psychological tests. He was one of the few psychologists who as early as the 1950s helped labor unions fight the use of inappropriate psychological tests in the selection of workers for employment, training, or advancement. In 1965, he testified before a subcommittee on Constitutional Rights of the US Senate Judiciary Committee on inappropriate use of personality tests (the MMPI) in federal agencies and submitted two technical papers, thought to be the first E/HF assessments of use of personality tests in employment. This hearing anticipated a series of US Supreme Court decisions that established both lack of adverse impact and jobrelatedness as key criteria for postemployment use of tests. After his retirement from teaching in 1977, K.U. served as a testing consultant for a series of labor unions, and as an expert witness on testing procedures and their validity in arbitration and court cases.
Influence as a Teacher.
K.U.’s impact on the E/HF field as a teacher (recognized by the HFES Fitts Award) was as dramatic as any of his other accomplishments. At UW he mentored some 60 graduate students during his tenure there. Testimonials from many after his death (e.g. Gould 1996) paid tribute to his goodness and generosity, and to how he had changed their lives, both personally and professionally. Many went on to play a prominent role as educators, researchers and/or practitioners in the E/HF field — an (admittedly incomplete) list includes Robert Arndt (consultant), Pat Coleman (US Center for Disease Control), John D. Gould (IBM, former HFES president), Frank Hatch (Institute for Kinaesthetics), Robert Henning (University of Connecticut), Vern Putz-Anderson and Steve Sauter (NIOSH), Michael Smith (UW), and Harvey Sussman (University of Texas).
Prepared by Thomas J. Smith
Coleman, P., Ruff, C., & Smith, K. U. (1970). Effects of feedback delay on eye-hand synchronism in steering behavior. The Journal of Applied Psychology, 54(3), 271–7. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/5431194
Smith, T. J., & Smith, K. U. (1985). Cybernetic factors in motor performance and development. Advances in Psychology, 27, 239-283. Retrieved from https://books.google.at/books?hl=de&lr=&id=I2Qu2jQj1nsC&oi=fnd&pg=PA239&dq=Cybernetic+factors
Gould, J. D., & Smith, K. U. (1964). Sensory feedback analysis of stereotelevision pursuit tracking. Journal of Applied Psychology, 48(3), 152. Retrieved from http://psycnet.apa.org/record/1965-06139-001
Harris, S., & Smith, K. U. (1953). Dimensional analysis of motion: V. An analytic test of psychomotor ability. Journal of Applied Psychology, 37(2), 136. Retrieved from http://psycnet.apa.org/record/1954-00405-001
Harris, S. J., & Smith, K. U. (1954). Dimensional analysis of motion: VII. Extent and direction of manipulative movements as factors in defining motions. Journal of Applied Psychology, 38(2), 126. Retrieved from http://psycnet.apa.org/record/1955-03200-001
Hecker, D., Green, D., & Smith, K. U. (1956). Dimensional analysis of motion: X. Experimental evaluation of a time-study problem. Journal of Applied Psychology, 40(4), 220. Retrieved from http://psycnet.apa.org/record/1957-06762-001
Henry, J. P., Junas, R., & Smith, K. U. (1967). Experimental Cybernetic Analysis of Delayed Feedback of Breath-Pressure Control. American Journal of Physical Medicine & Rehabilitation, 46(4), 1317-1331. Retrieved from http://journals.lww.com/ajpmr/Abstract/1967/08000/Experimental_Cybernetic_Analysis_of_Delayed.1.aspx
Jones, O. R., & Smith, K. U. (1951). Measurement of supervisory ability. Journal of Applied Psychology, 35(3), 146. Retrieved from http://psycnet.apa.org/record/1952-01126-001
KU Smith. (1973). Physiological and sensory feedback of the motor system: neural metabolic integration for energy regulation in behavior. In J. Maser (Ed.), Efferent Organization and the Integration of Behavior. (pp. 19–66). New York: Academic Press. Retrieved from https://www.sciencedirect.com/science/article/pii/B9780124769502500087
Lincoln, R. S., & Smith, K. U. (1951). Transfer of training in tracking performance at different target speeds. Journal of Applied Psychology, 35(5), 358. http://psycnet.apa.org/record/1952-03863-001
Lincoln, R. S., & Smith, K. U. (1952). Visual tracking: II. Effects of brightness and width of target. Journal of Applied Psychology, 36(6), 417. Retrieved from http://psycnet.apa.org/record/1953-06839-001
McDermid, C., & Smith, K. U. (1964). Compensatory reaction to angularly displaced visual feedback in behavior. Journal of Applied Psychology, 48(1), 63. Retrieved from http://psycnet.apa.org/record/1964-07046-001
Nesberg, L. S., & Smith, K. U. (1950). Measurement of a complex psychomotor performance by means of a printed test. Journal of Applied Psychology, 34(5), 309. Retrieved from http://psycnet.apa.org/record/1952-00558-001
Pearl, B. E., Simon, J. R., & Smith, K. U. (1955). Visual tracking: IV. Interrelations of target speed and aided-tracking ratio in defining tracing accuracy. Journal of Applied Psychology, 39(4), 209. Retrieved from http://psycnet.apa.org/record/1956-05388-001
Putz, V., & Smith, K. (1971). Pearl, B. E., Simon, J. R., & Smith, K. U. (1955). Visual tracking: IV. Interrelations of target speed and aided-tracking ratio in defining tracing accuracy. Journal of Applied Psychology, 39(4), 209. Retrieved from http://psycnet.apa.org/record/1956-05388-001
Simon, J., & Smader, R. (1955). Simon, J. R., & Smader, R. C. (1955). Dimensional analysis of motion: VIII. The role of visual discrimination in motion cycles. Journal of Applied Psychology, 39(1), 5. Retrieved from http://psycnet.apa.org/record/1956-01789-001
Simon, J. R., & Smith, K. U. (1956). Theory and analysis of component errors in aided pursuit tracking in relation to target speed and aided-tracking time constant. Journal of Applied Psychology, 40(6), 367. Retrieved from http://psycnet.apa.org/record/1958-02228-001
Smader, R., & Smith, K. U. (1953). Dimensional analysis of motion: VI. The component movements of assembly motions. Journal of Applied Psychology, 37(4), 308. Retrieved from http://psycnet.apa.org/record/1954-05550-001
Smith, K. U., & Putz, V. (1970). Feedback factors in steering and tracking behavior. The Journal of Applied Psychology, 54(2), 176–83. Retrieved from http://www.safetylit.org/citations/index.php?fuseaction=citations.viewdetails&citationIds%5B%5D=citjournalarticle_112309_38
Smith, K. U. (1966). Cybernetic theory and analysis of learning. Acquisition of skill, 425-482. Retrieved from https://scholar.google.at/scholar?hl=de&as_sdt=0%2C5&q=Cybernetic+theory+and+analysis+of+learning.
Smith, K. (1990). Hazard management: Principles, applications and evaluation. … of the Human Factors and Ergonomics Society Annual …. Retrieved from http://pro.sagepub.com/content/34/14/1020.short
Smith, K. (1941). Experiments on the neural basis of movement vision. Journal of Experimental Psychology. Retrieved from http://scholar.google.at/scholar?q=Experiments+on+the+neural+basis+of+movement+vision.&btnG=&hl=de&as_sdt=0#0
Smith, K. (1972). Cybernetic psychology. The Psychomotor Domain. Retrieved from http://scholar.google.at/scholar?q=Cybernetic+psychology.&btnG=&hl=de&as_sdt=0#0
Smith, K. (1940). The neural centers concerned in the mediation of apparent movement vision. Journal of Experimental Psychology. Retrieved from http://scholar.google.at/scholar?q=The+neural+centers+concerned+in+the+mediation+of+apparent+movement+vision.&btnG=&hl=de&as_sdt=0#0
Smith, K. (1972). Social tracking in the development of educational visual skills. American Journal of Optometry and Archives of …. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/4500612
Sensory feedback analysis in medical research. I. Delayed sensory feedback in behavior and neural function. American Journal of Physical …. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/14084957
Smith, K., & Arndt, R. (1970). Self-generated control mechanisms in posture. American Journal of Physical Medicine & …. Retrieved from http://journals.lww.com/ajpmr/Abstract/1970/08000/Self_Generated_Control_Mechanisms_in_Posture.2.aspx
Smith, K., & Bloom, R. (1956). The electronic handwriting analyzer and motion study of writing. Journal of …. Retrieved from http://scholar.google.at/scholar?q=The+electronic+Handwriting+analyzer+and+motion+study+of+writing.&btnG=&hl=de&as_sdt=0#0
Smith, K. U., & Bojar, S. (1938). The nature of optokinetic reactions in mammals and their significance in the experimental analysis of the neural mechanisms of visual functions. Psychological Bulletin, 35(4), 193. Retrieved from http://psycnet.apa.org/record/1938-03405-001
Smith, K., Cambria, R., & Steffan, J. (1964). Sensory-feedback analysis of reading. Journal of …. Retrieved from http://scholar.google.at/scholar?q=Sensory-feedback+analysis+of+reading.&btnG=&hl=de&as_sdt=0#0
Smith, K., & Gould, J. (1964). Sensory-feedback analysis of behavior in stereotelevised visual fields. Journal of …. Retrieved from http://scholar.google.at/scholar?q=Sensory-feedback+analysis+of+behavior+in+stereotelevised+visual+fields.&btnG=&hl=de&as_sdt=0#0
Smith, K., & Henry, J. (1967). Cybernetic foundations for rehabilitation. … of Physical Medicine & Rehabilitation. Retrieved from http://journals.lww.com/ajpmr/Abstract/1967/02000/Cybernetic_Foundations_for_Rehabilitation.30.aspx
Smith, K., & Kao, H. (1971). Social feedback: determination of social learning. The Journal of Nervous and Mental Disease. Retrieved from http://journals.lww.com/jonmd/Abstract/1971/04000/Social_Feedback__Determination_of_Social_Learning.5.aspx
Smith, K., Lingh, G., & Eischens, R. (1970). Effects of sound on postural control. The Journal of Applied …. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/5431191
Smith, K., & Putz, V. (1970). Feedback analysis of learning and performance in steering and tracking behavior. The Journal of Applied Psychology. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/5431192
Smith, K., Putz, V., & Molitor, K. (1970). Delayed retinal feedback of eye movements: a dynamic basis of perceptual disabilities. The Journal of Applied Psychology. Retrieved from http://europepmc.org/abstract/MED/5496371
Smith, K., & Ramana, D. (1970). Feedback Analysis of Posture As A Body Tracking Mechanism. American Journal of Physical …. Retrieved from http://journals.lww.com/ajpmr/Abstract/1970/04000/Feedback_Analysis_of_Posture_As_A_Body_Tracking.2.aspx
Smith, K., Schremser, R., & Putz, V. (1971). Binocular coordination in reading. Journal of Applied Psychology. Retrieved from http://scholar.google.at/scholar?cluster=12330922818320533379&hl=de&as_sdt=0#2
Smith, K., & Smith, M. (1973). Psychology: an introduction to behavior science. Retrieved from http://www.getcited.org/pub/101325984
Smith, K., & Smith, M. (1966). Cybernetic principles of learning and educational design. Retrieved from http://www.eric.ed.gov/ERICWebPortal/recordDetail?accno=ED032750
Smith, K., & Smith, T. (1970). Feedback mechanisms of athletic skill and learning. Psychology of Motor Learning. Chicago: Athletic …. Retrieved from http://scholar.google.at/scholar?q=Feedback+mechanisms+of+athletic+skill+and+learning.&btnG=&hl=de&as_sdt=0#0
Smith, K., & Smith, W. (1958). The behavior of man: Introduction to psychology. Retrieved from http://psycnet.apa.org/psycinfo/2009-16543-000/
Smith, K., Smith, W., & Smith, M. (1962). Perception and motion: an analysis of space-structured behavior. Retrieved from http://scholar.google.at/scholar?hl=de&q=Perception+and+motion%3A+an+analysis+of+space-structured+behavior.&btnG=&lr=#0
Smith, K., & Sussman, H. (1969). Cybernetic theory and analysis of motor learning and memory. Principles of Skill Acquisition. New York, NY, Academic …. Retrieved from http://scholar.google.at/scholar?q=Cybernetic+theory+and+analysis+of+motor+learning+and+memory.&btnG=&hl=de&as_sdt=0#0
Smith, K., & Sussman, H. (1970). Delayed feedback in steering during learning and transfer of learning(Steering behavior during learning as function of self generated stimuli by movement. Journal of Applied Psychology. Retrieved from http://scholar.google.at/scholar?q=Delayed+Feedback+in+steering+during+learning+and+transfer+of+learning&btnG=&hl=de&as_sdt=0#0
Smith, T., Henning, R., & Smith, K. (1994). Sources of performance variability. Design of Work and …. Retrieved from http://books.google.at/books?hl=de&lr=&id=FEPf-loPPuYC&oi=fnd&pg=PA273&dq=Interactive+performance+in+space+–+The+role+of+perturbed+sensory+feedback.&ots=BdFZX86s-K&sig=AGXTSn5B-iUyT5XHBNUByRhTBl4
Smith, T., & Smith, K. (1988). The social cybernetics of human interaction with automated systems. … on Ergonomics of Hybrid Automated Systems I. Retrieved from http://dl.acm.org/citation.cfm?id=58290
Smith, T. J., & Smith, K. U. (1987). Feedback-control mechanisms of human behavior. In G. Salvendy (Ed.), Handbook of human factors (pp. 251-293). Oxford, England: John Wiley. Retrieved from http://psycnet.apa.org/record/1987-97061-011
Smith, T. J., Smith, R. L., Stuart, M. A., Smith, S. T., & Smith, K. U. (1989, September). Interactive performance in space—the role of perturbed sensory feedback. In Proceedings of the third international conference on human-computer interaction, Vol. 1 on Work with computers: organizational, management, stress and health aspects (pp. 484-495). Elsevier Science Inc.. Retrieved from http://dl.acm.org/citation.cfm?id=92252
Sussman, H., & Smith, K. U. (1970). Sensory-feedback persistence in determining memory. Journal of Applied Psychology, 54(6), 503. Retrieved from http://psycnet.apa.org/record/1971-03472-001
Ting, T., Smith, M., & Smith, K. U. (1972). Social feedback factors in rehabilitative processes and learning. American Journal of Physical Medicine & Rehabilitation, 51(2), 86-101. Retrieved from http://journals.lww.com/ajpmr/Abstract/1972/04000/Social_Feedback_Factors_in_Rehabilitative.4.aspx
Von Trebra, P., & Smith, K. U. (1952). The dimensional analysis of motion: IV. Transfer effects and direction of movement. Journal of Applied Psychology, 36(5), 348. Retrieved from http://psycnet.apa.org/record/1953-04893-001
Wehrkamp, R., & Smith, K. U. (1952). Dimensional analysis of motion: II. Travel-distance effects. Journal of Applied Psychology, 36(3), 201. Retrieved from http://psycnet.apa.org/record/1953-03096-001
Davis, R., Wehrkamp, R., & Smith, K. U. (1951). Dimensional analysis of motion: I. Effects of laterality and movement direction. Journal of Applied Psychology, 35(5), 363. Retrieved from http://psycnet.apa.org/record/1952-04216-001
Smith, K. U., Kaplan, R., & Kao, H. (1970). Experimental systems analysis of simulated vehicle steering and safety training. Journal of Applied Psychology, 54(4), 364. Redtrieved from http://psycnet.apa.org/record/1970-21722-001
Rubin, G., Von Trebra, P., & Smith, K. U. (1952). Dimensional analysis of motion: III. Complexity of movement pattern. Journal of Applied Psychology, 36(4), 272. Retrieved from http://psycnet.apa.org/record/1953-03833-001