Bio


Carl Wieman holds a joint appointment as Professor of Physics and of the Graduate School of Education. He has done extensive experimental research in atomic and optical physics. His current intellectual focus is now on undergraduate physics and science education. He has pioneered the use of experimental techniques to evaluate the effectiveness of various teaching strategies for physics and other sciences, and served as Associate Director for Science in the White House Office of Science and Technology Policy.

Academic Appointments


Honors & Awards


  • Carnegie US University Professor of the Year, Carnegie Foundation for the Advancement of Teaching (2003)
  • Nobel Prize in Physics 2001, Nobel Foundation (2001)

Professional Education


  • Ph.D., Stanford University, Physics (1977)
  • B.S., MIT, Physics (1973)

Research Interests


  • Brain and Learning Sciences
  • Higher Education
  • Science Education
  • Teachers and Teaching

Current Research and Scholarly Interests


The Wieman group’s research generally focuses on the nature of expertise in science and engineering, particularly physics, and how that expertise is best learned, measured, and taught. This involves a range of approaches, including individual cognitive interviews, laboratory experiments, and classroom interventions with controls for comparisons. We are also looking at how different classroom practices impact the attitudes and learning of different demographic groups.

Some current projects include:
1. Investigating problem solving strategies. We are examining the detailed components in problem solving to determine how these combine to achieve problem solving success, and how the strengths and weaknesses of a learners strategy can be measured and then improved. This work involves physics based computer simulations where students decide what information to seek, how to interpret the information they get, and then how they choose to act on that information. The goals of this research are, primarily, to identify which aspects of problem solving strategies pave the way to expertise and how to teach these effectively.

2. Cognitive principles for instructional design
Although current “active learning” efforts have been shown to provide better learning outcomes than traditional instructional methods, there is currently little guidance on how to design such materials to best support learning. We are designing, implementing, and studying instructional materials that take into account findings on human cognition, such as the benefits of inventing from a series of contrasting cases (e.g. Schwartz et al., 2011). By studying the efficacy of these materials, we hope to provide instructors, curriculum developers, and researchers with new principles for designing effective instructional materials for typical classroom instruction. A particular focus at this time is the use and learning of mechanistic reasoning, a fundamental component of physic expertise, as well as many other sciences.


3. The assessment and learning of adaptive medical expertise. Although medical education focuses heavily on mastery factual information and procedures under carefully identified conditions, medical practice takes place in a much less controlled environment. There are many other possibly relevant and irrelevant factors a doctor must take into account. This calls for adaptive expertise, the capability to operate in new contexts and learn new things as needed. We are working on the better assessment of such adaptive expertise and ultimately on the improvement of medical teaching to better teach it.

2024-25 Courses


Stanford Advisees


All Publications


  • Characterizing decision-making opportunities in undergraduate physics coursework PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Montgomery, B. J., Price, A. M., Wieman, C. E. 2024; 20 (2)
  • Cognitive framework for blended mathematical sensemaking in science INTERNATIONAL JOURNAL OF STEM EDUCATION Kaldaras, L., Wieman, C. 2023; 10 (1)
  • Equitable approach to introductory calculus-based physics courses focused on problem solving PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E., Salehi, S., Sackeyfio, S., Mohamed-Hinds, N., Wieman, C. 2022; 18 (2)
  • An accurate and practical method for assessing science and engineering problem-solving expertise INTERNATIONAL JOURNAL OF SCIENCE EDUCATION Price, A., Salehi, S., Burkholder, E., Kim, C., Isava, V., Flynn, M., Wieman, C. 2022
  • A Detailed Characterization of the Expert Problem-Solving Process in Science and Engineering: Guidance for Teaching and Assessment. CBE life sciences education Price, A. M., Kim, C. J., Burkholder, E. W., Fritz, A. V., Wieman, C. E. 2021; 20 (3): ar43

    Abstract

    A primary goal of science and engineering (S&E) education is to produce good problem solvers, but how to best teach and measure the quality of problem solving remains unclear. The process is complex, multifaceted, and not fully characterized. Here, we present a detailed characterization of the S&E problem-solving process as a set of specific interlinked decisions. This framework of decisions is empirically grounded and describes the entire process. To develop this, we interviewed 52 successful scientists and engineers ("experts") spanning different disciplines, including biology and medicine. They described how they solved a typical but important problem in their work, and we analyzed the interviews in terms of decisions made. Surprisingly, we found that across all experts and fields, the solution process was framed around making a set of just 29 specific decisions. We also found that the process of making those discipline-general decisions (selecting between alternative actions) relied heavily on domain-specific predictive models that embodied the relevant disciplinary knowledge. This set of decisions provides a guide for the detailed measurement and teaching of S&E problem solving. This decision framework also provides a more specific, complete, and empirically based description of the "practices" of science.

    View details for DOI 10.1187/cbe.20-12-0276

    View details for PubMedID 34388005

  • Expertise in University Teaching & the Implications for Teaching Effectiveness, Evaluation & Training DAEDALUS Wieman, C. 2019; 148 (4): 47–78
  • What do AP physics courses teach and the AP physics exam measure? PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E. W., Wieman, C. E. 2019; 15 (2)
  • Demographic gaps or preparation gaps?: The large impact of incoming preparation on performance of students in introductory physics PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Salehi, S., Burkholder, E., Lepage, G., Pollock, S., Wieman, C. 2019; 15 (2)
  • Enhancing Diversity in Undergraduate Science: Self-Efficacy Drives Performance Gains with Active Learning. CBE life sciences education Ballen, C. J., Wieman, C., Salehi, S., Searle, J. B., Zamudio, K. R. 2017; 16 (4)

    Abstract

    Efforts to retain underrepresented minority (URM) students in science, technology, engineering, and mathematics (STEM) have shown only limited success in higher education, due in part to a persistent achievement gap between students from historically underrepresented and well-represented backgrounds. To test the hypothesis that active learning disproportionately benefits URM students, we quantified the effects of traditional versus active learning on student academic performance, science self-efficacy, and sense of social belonging in a large (more than 250 students) introductory STEM course. A transition to active learning closed the gap in learning gains between non-URM and URM students and led to an increase in science self-efficacy for all students. Sense of social belonging also increased significantly with active learning, but only for non-URM students. Through structural equation modeling, we demonstrate that, for URM students, the increase in self-efficacy mediated the positive effect of active-learning pedagogy on two metrics of student performance. Our results add to a growing body of research that supports varied and inclusive teaching as one pathway to a diversified STEM workforce.

    View details for DOI 10.1187/cbe.16-12-0344

    View details for PubMedID 29054921

    View details for PubMedCentralID PMC5749958

  • Measuring the impact of an instructional laboratory on the learning of introductory physics AMERICAN JOURNAL OF PHYSICS Wieman, C., Holmes, N. G. 2015; 83 (11): 972-978

    View details for DOI 10.1119/1.4931717

    View details for Web of Science ID 000363529400014

  • Teaching critical thinking PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Holmes, N. G., Wieman, C. E., Bonn, D. A. 2015; 112 (36): 11199-11204

    Abstract

    The ability to make decisions based on data, with its inherent uncertainties and variability, is a complex and vital skill in the modern world. The need for such quantitative critical thinking occurs in many different contexts, and although it is an important goal of education, that goal is seldom being achieved. We argue that the key element for developing this ability is repeated practice in making decisions based on data, with feedback on those decisions. We demonstrate a structure for providing suitable practice that can be applied in any instructional setting that involves the acquisition of data and relating that data to scientific models. This study reports the results of applying that structure in an introductory physics laboratory course. Students in an experimental condition were repeatedly instructed to make and act on quantitative comparisons between datasets, and between data and models, an approach that is common to all science disciplines. These instructions were slowly faded across the course. After the instructions had been removed, students in the experimental condition were 12 times more likely to spontaneously propose or make changes to improve their experimental methods than a control group, who performed traditional experimental activities. The students in the experimental condition were also four times more likely to identify and explain a limitation of a physical model using their data. Students in the experimental condition also showed much more sophisticated reasoning about their data. These differences between the groups were seen to persist into a subsequent course taken the following year.

    View details for DOI 10.1073/pnas.1505329112

    View details for Web of Science ID 000360994900034

    View details for PubMedID 26283351

    View details for PubMedCentralID PMC4568696

  • Analyzing the many skills involved in solving complex physics problems AMERICAN JOURNAL OF PHYSICS Adams, W. K., Wieman, C. E. 2015; 83 (5): 459-467

    View details for DOI 10.1119/1.4913923

    View details for Web of Science ID 000353306500010

  • The teaching practices inventory: a new tool for characterizing college and university teaching in mathematics and science. CBE life sciences education Wieman, C., Gilbert, S. 2014; 13 (3): 552-569

    Abstract

    We have created an inventory to characterize the teaching practices used in science and mathematics courses. This inventory can aid instructors and departments in reflecting on their teaching. It has been tested with several hundred university instructors and courses from mathematics and four science disciplines. Most instructors complete the inventory in 10 min or less, and the results allow meaningful comparisons of the teaching used for the different courses and instructors within a department and across different departments. We also show how the inventory results can be used to gauge the extent of use of research-based teaching practices, and we illustrate this with the inventory results for five departments. These results show the high degree of discrimination provided by the inventory, as well as its effectiveness in tracking the increase in the use of research-based teaching practices.

    View details for DOI 10.1187/cbe.14-02-0023

    View details for PubMedID 25185237

    View details for PubMedCentralID PMC4152215

  • Large-scale comparison of science teaching methods sends clear message. Proceedings of the National Academy of Sciences of the United States of America Wieman, C. E. 2014; 111 (23): 8319-8320

    View details for DOI 10.1073/pnas.1407304111

    View details for PubMedID 24853505

    View details for PubMedCentralID PMC4060683

  • Psychological insights for improved physics teaching PHYSICS TODAY Aguilar, L., Walton, G., Wieman, C. 2014; 67 (5): 43-49

    View details for DOI 10.1063/PT.3.2383

    View details for Web of Science ID 000341446300018

  • Use of research-based instructional strategies: How to avoid faculty quitting PHYSICAL REVIEW SPECIAL TOPICS-PHYSICS EDUCATION RESEARCH Wieman, C., Deslauriers, L., Gilley, B. 2013; 9 (2)
  • Employing technology-enhanced feedback and scaffolding to support the development of deep science understanding using computer simulations INTERNATIONAL JOURNAL OF STEM EDUCATION Kaldaras, L., Wang, K. D., Nardo, J. E., Price, A., Perkins, K., Wieman, C., Salehi, S. 2024; 11 (1)
  • Exploring the learning experiences of neurodivergent college students in STEM courses JOURNAL OF RESEARCH IN SPECIAL EDUCATIONAL NEEDS Wang, K. D., Mccool, J., Wieman, C. 2024
  • Examining the potential and pitfalls of ChatGPT in science and engineering problem-solving FRONTIERS IN EDUCATION Wang, K. D., Burkholder, E., Wieman, C., Salehi, S., Haber, N. 2024; 8
  • Can Crowdsourcing Platforms Be Useful for Educational Research? Wang, K. D., Chen, Z., Wieman, C., Assoc Computing Machinery ASSOC COMPUTING MACHINERY. 2024: 416-425
  • Global perspectives of the impact of the COVID-19 pandemic on learning science in higher education. PloS one Salehi, S., Ballen, C. J., Bolander Laksov, K., Ismayilova, K., Poronnik, P., Ross, P. M., Tzioumis, V., Wieman, C. 2023; 18 (12): e0294821

    Abstract

    The COVID-19 pandemic required higher education institutions to rapidly transition to Emergency Remote Instruction (ERI) with little preparation. Discussions are now underway globally to learn the lessons of COVID-19 and to use this knowledge to shape the future of learning science in higher education. In this study, we examined the experiences of instructors and students to ERI in three universities across three continents-America, Europe, and Australia. We measured the instructional strategies used by instructors including assessment types, and interaction opportunities during and outside class schedules. We also measured the learning challenges experienced by students including planning, distractions, technology, learning resources, their views on educational quality and what characterized quality interactions during ERI. Our findings suggest that most instructional strategies used by instructors changed little during ERI, although the nature of instructor and student interactions during class relied more heavily on technology. Students reported significant learning challenges which included distractions from their physical and social media environments and access to technology. Both instructors and students reported that interactions with each other and their peers were concerningly low, albeit similar to pre COVID-19 pandemic levels. There were differences in the perceptions of instructors and students on whether instructor-student interactions were better or worse online. Common among all universities, there was a large proportion of students reporting mental health and work-related stress. Lessons to be learned from the COVID-19 pandemic include ensuring more support for instructors to implement effective and equitable pedagogies and an increased recognition of the importance of practicals, and the social, interactive and hands-on aspects of learning science in higher education. We predict that the incorporation of active learning pedagogies and strategies which increase student engagement and foster a sense of belonging will be ongoing global challenges for learning science in a post COVID-19 campus.

    View details for DOI 10.1371/journal.pone.0294821

    View details for PubMedID 38060473

    View details for PubMedCentralID PMC10703257

  • Instructional model for teaching blended math-science sensemaking in undergraduate science, technology, engineering, and math courses using computer simulations PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Kaldaras, L., Wieman, C. 2023; 19 (2)
  • Impact of Prompting Engineering Undergraduates to Reflect on Their Problem-Solving Skills INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION Salehi, S., Wang, K. D., Flynn, M., Wieman, C. 2023; 39 (2): 653-667
  • How traditional physics coursework limits problem-solving opportunities Montgomery, B. J., Price, A. M., Wieman, C. E., Jones, D., Ryan, Q., Pawl, A. AMER ASSOC PHYSICS TEACHERS. 2023: 230-235
  • How to become a successful physicist PHYSICS TODAY Wieman, C. 2022; 75 (9): 46-52

    View details for DOI 10.1063/PT.3.5082

    View details for Web of Science ID 000860478400011

  • Absence of a COVID-induced academic drop in high-school physics learning PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E. W., Wieman, C. E. 2022; 18 (2)
  • Perspectives on Active Learning: Challenges for Equitable Active Learning Implementation br JOURNAL OF CHEMICAL EDUCATION Nardo, J., Chapman, N. C., Shi, E., Wieman, C., Salehi, S. 2022; 99 (4): 1691-1699
  • Perspectives on Active Learning: Challenges for Equitable Active Learning Implementation JOURNAL OF CHEMICAL EDUCATION Nardo, J., Chapman, N. C., Shi, E., Wieman, C., Salehi, S. 2022
  • Inclusive Instructional Practices: Course Design, Implementation, and Discourse FRONTIERS IN EDUCATION Salehi, S., Ballen, C. J., Trujillo, G., Wieman, C. 2021; 6
  • Evidence-Based Principles for Worksheet Design PHYSICS TEACHER Burkholder, E., Mohamed-Hinds, N., Wieman, C. 2021; 59 (6): 402-403

    View details for DOI 10.1119/5.0020091

    View details for Web of Science ID 000739172900008

  • Validated diagnostic test for introductory physics course placement PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E., Wang, K., Wieman, C. 2021; 17 (1)
  • Importance of math prerequisites for performance in introductory physics PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E. W., Murillo-Gonzalez, G., Wieman, C. 2021; 17 (1)
  • Mixed results from a multiple regression analysis of supplemental instruction courses in introductory physics. PloS one Burkholder, E., Salehi, S., Wieman, C. E. 2021; 16 (4): e0249086

    Abstract

    Providing less prepared students with supplemental instruction (SI) in introductory STEM courses has long been used as a model in math, chemistry, and biology education to improve student performance, but this model has received little attention in physics education research. We analyzed the course performance of students enrolled in SI courses for introductory mechanics and electricity and magnetism (E&M) at Stanford University compared with those not enrolled in the SI courses over a two-year period. We calculated the benefit of the SI course using multiple linear regression to control for students' level of high school physics and math preparation. We found that the SI course had a significant positive effect on student performance in E&M, but that an SI course with a nearly identical format had no effect on student performance in mechanics. We explored several different potential explanations for why this might be the case and were unable to find any that could explain this difference. This suggests that there are complexities in the design of SI courses that are not fully understood or captured by existing theories as to how they work.

    View details for DOI 10.1371/journal.pone.0249086

    View details for PubMedID 33793607

  • Examining the Links between Log Data and Reflective Problem-solving Practices in An Interactive Task Wang, K., Nair, K., Wieman, C., Assoc Comp Machinery ASSOC COMPUTING MACHINERY. 2021: 525-532
  • Response to "Interpret with Caution: COPUS Instructional Styles May Not Differ in Terms of Practices That Support Student Learning," by Melody McConnell, Jeffrey Boyer, Lisa M. Montplaisir, Jessie B. Arneson, Rachel L. S. Harding, Brian Farlow, and Erika G. Offerdahl. CBE life sciences education Wieman, C. 2021; 20 (3): le1

    View details for DOI 10.1187/cbe.21-05-0126

    View details for PubMedID 34283631

  • Impact of Decision-Making in Capstone Design Courses on Students' Ability to Solve Authentic Problems INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION Burkholder, E., Wieman, C. 2021; 37 (3): 650-662
  • Characterizing the mathematical problem-solving strategies of transitioning novice physics students PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Burkholder, E., Blackmon, L., Wieman, C. 2020; 16 (2)
  • Developing scientific decision making by structuring and supporting student agency PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Holmes, N. G., Keep, B., Wieman, C. E. 2020; 16 (1)
  • Evaluating the problem-solving skills of graduating chemical engineering students Education for Chemical Engineers Burkholder, E., Hwang, L. Y., Wieman, C. 2020; 34: 68-77
  • Comparing problem-solving across capstone design courses in chemical engineering Burkholder, E., Wieman, C., IEEE IEEE. 2020
  • What factors impact student performance in introductory physics? PloS one Burkholder, E. n., Blackmon, L. n., Wieman, C. n. 2020; 15 (12): e0244146

    Abstract

    In a previous study, we found that students' incoming preparation in physics-crudely measured by concept inventory prescores and math SAT or ACT scores-explains 34% of the variation in Physics 1 final exam scores at Stanford University. In this study, we sought to understand the large variation in exam scores not explained by these measures of incoming preparation. Why are some students' successful in physics 1 independent of their preparation? To answer this question, we interviewed 34 students with particularly low concept inventory prescores and math SAT/ACT scores about their experiences in the course. We unexpectedly found a set of common practices and attitudes. We found that students' use of instructional resources had relatively little impact on course performance, while student characteristics, student attitudes, and students' interactions outside the classroom all had a more substantial impact on course performance. These results offer some guidance as to how instructors might help all students succeed in introductory physics courses.

    View details for DOI 10.1371/journal.pone.0244146

    View details for PubMedID 33332432

  • Exploring bias in mechanical engineering students' perceptions of classmates. PloS one Salehi, S., Holmes, N. G., Wieman, C. 2019; 14 (3): e0212477

    Abstract

    Gender disparity in science, technology, engineering, and math (STEM) fields is an on-going challenge. Gender bias is one of the possible mechanisms leading to such disparities and has been extensively studied. Previous work showed that there was a gender bias in how students perceived the competence of their peers in undergraduate biology courses. We examined whether there was a similar gender bias in a mechanical engineering course. We conducted the study in two offerings of the course, which used different instructional practices. We found no gender bias in peer perceptions of competence in either of the offerings. However, we did see that the offerings' different instructional practices affected aspects of classroom climate, including: the number of peers who were perceived to be particularly knowledgeable, the richness of the associated network of connections between students, students' familiarity with each other, and their perceptions about the course environment. These results suggest that negative bias against female students in peer perception is not universal, either across institutions or across STEM fields, and that instructional methods may have an impact on classroom climate.

    View details for PubMedID 30845229

  • Experiences in improving introductory physics labs Reply PHYSICS TODAY Holmes, N. G., Wieman, C. E. 2018; 71 (7): 13

    View details for DOI 10.1063/PT.3.3962

    View details for Web of Science ID 000437282800005

  • Tools for Science Inquiry Learning: Tool Affordances, Experimentation Strategies, and Conceptual Understanding JOURNAL OF SCIENCE EDUCATION AND TECHNOLOGY Bumbacher, E., Salehi, S., Wieman, C., Blikstein, P. 2018; 27 (3): 215–35
  • Introductory physics labs: WE CAN DO BETTER PHYSICS TODAY Holmes, N. G., Wieman, C. E. 2018; 71 (1): 38–45

    View details for DOI 10.1063/PT.3.3816

    View details for Web of Science ID 000419142900013

  • Enhancing Diversity in Undergraduate Science: Self-Efficacy Drives Performance Gains with Active Learning CBE-LIFE SCIENCES EDUCATION Ballen, C. J., Wieman, C., Salehi, S., Searle, J. B., Zamudio, K. R. 2017; 16 (4)
  • The Connection Between Teaching Methods and Attribution Errors EDUCATIONAL PSYCHOLOGY REVIEW Wieman, C., Welsh, A. 2016; 28 (3): 645-648
  • Examining and contrasting the cognitive activities engaged in undergraduate research experiences and lab courses PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Holmes, N. G., Wieman, C. E. 2016; 12 (2)
  • Toward instructional design principles: Inducing Faraday's law with contrasting cases PHYSICAL REVIEW PHYSICS EDUCATION RESEARCH Kuo, E., Wieman, C. E. 2016; 12 (1)
  • Concepts First, Jargon Second Improves Student Articulation of Understanding BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION McDonnell, L., Barker, M. K., Wieman, C. 2016; 44 (1): 12-19

    View details for DOI 10.1002/bmb.20922

    View details for Web of Science ID 000373010200002

  • Seeking instructional specificity: An example from analogical instruction PHYSICAL REVIEW SPECIAL TOPICS-PHYSICS EDUCATION RESEARCH Kuo, E., Wieman, C. E. 2015; 11 (2)
  • Educational transformation in upper-division physics: The Science Education Initiative model, outcomes, and lessons learned PHYSICAL REVIEW SPECIAL TOPICS-PHYSICS EDUCATION RESEARCH Chasteen, S. V., Wilcox, B., Caballero, M. D., Perkins, K. K., Pollock, S. J., Wieman, C. E. 2015; 11 (2)
  • Transforming a fourth year modern optics course using a deliberate practice framework PHYSICAL REVIEW SPECIAL TOPICS-PHYSICS EDUCATION RESEARCH Jones, D. J., Madison, K. W., Wieman, C. E. 2015; 11 (2)
  • Comparative Cognitive Task Analyses of Experimental Science and Instructional Laboratory Courses PHYSICS TEACHER Wieman, C. 2015; 53 (6): 349-351

    View details for DOI 10.1119/1.4928349

    View details for Web of Science ID 000365798300009

  • The Similarities Between Research in Education and Research in the Hard Sciences EDUCATIONAL RESEARCHER Wieman, C. E. 2014; 43 (1): 12-14
  • PRECISION-MEASUREMENT OF THE 1S LAMB SHIFT AND OF THE 1S-2S ISOTOPE SHIFT OF HYDROGEN AND DEUTERIUM PHYSICAL REVIEW A Wieman, C., Hansch, T. W. 1980; 22 (1): 192-205
  • DOPPLER-FREE LASER POLARIZATION SPECTROSCOPY PHYSICAL REVIEW LETTERS Wieman, C., Hansch, T. W. 1976; 36 (20): 1170-1173
  • DOPPLER-FREE 2-PHOTON SPECTROSCOPY OF HYDROGEN 1S-2S PHYSICAL REVIEW LETTERS Hansch, T. W., Lee, S. A., Wallenstein, R., Wieman, C. 1975; 34 (6): 307-309
  • HIGH-RESOLUTION MEASUREMENT OF RESPONSE OF AN ISOLATED BUBBLE-DOMAIN TO PULSED MAGNETIC-FIELDS IEEE TRANSACTIONS ON MAGNETICS Brown, B. R., Henry, G. R., KOEPCKE, R. W., Wieman, C. E. 1975; 11 (5): 1391-1393