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Theodore Cohn

IN MEMORIAM

Theodore E. Cohn

Professor of Vision Science

Professor of Bioengineering

UC Berkeley

1941 – 2006

  

Theodore E. Cohn, professor of vision science in the School of Optometry and professor of bioengineering, died at age 64 on May 25, 2006, at Alta Bates Hospital in Berkeley, following a three-year battle with lymphoma. He was a leading researcher in signal detection theory and its real-world applications, as well as an outstanding educator and mentor.

 

Born on September 5, 1941 in Highland Park, Illinois, Cohn was the grandson of Lithuanian immigrants. He received a B.S. in electrical engineering from the Massachusetts Institute of Technology (MIT) and then attended the University of Michigan, where he received three degrees: a M.S. in bioengineering in 1965, a M.A. in mathematics in 1966, and a Ph.D. in bioengineering in 1969. In 1970, he was appointed an assistant professor of physiological optics at the University of California, Berkeley, the institution where he would spend his entire professional career. In 1998, Cohn accepted an appointment in the newly-established Department of Bioengineering, while continuing as a professor in the School of Optometry.

 

In his 36 years on the Berkeley faculty, Professor Cohn’s research spanned a range of fields. From studying how people pick signals out of cluttered backgrounds, to elucidating neural responses of visual input, to applying that knowledge to the design of improved traffic safety devices, his work was united by the common theme of visual detection.

 

Cohn’s interest in signal detection theory began in college. Both MIT and the University of Michigan were hotbeds of research in the field, which provides models based on precise language and graphic notation for analyzing how people make decisions in the face of uncertain events. This field of applied science emerged during World War II, when the military began to explore how radar operators could detect signals of incoming airplanes in the clutter of background noise on their screens. One of Cohn’s contributions was to quantify an ideal human observer and how that observer would react when uncertainty is present. He did a number of elegant experiments to show that there were important effects if the observer did not know where, when or for what to look. The key point he stressed is that whether you see something or not, and how reliably you see it, does not depend only on the magnitude of the electrical response, but also on the reproducibility of the response.

 

Though most of his experimental work addressed the limits of human visual performance, Professor Cohn also studied the electrical signals passing from the eye to the brain in frogs, cats and locusts, noting that the eye’s response to repetitions of a visual stimulus—a flash of light, for example—varies from one occurrence to the next. The same light flash presented many times would produce a slightly different electrical signal to the brain each time. He demonstrated both theoretically and by experiment that photon fluctuations could account for the increased visibility of a decrement as opposed to an equal increment of light. In addition, he was a pioneer for using light-emitting diodes (LEDs) for studying human vision. This early research may have inspired his later work on practical applications of LEDs in traffic signals.

 

Ted was most concerned about the impact of his work on people and their world. He derived great pleasure from solving problems in vision science, but he also actively pursued how new knowledge could help people simply and directly.

 

For most of his last 15 years, Ted Cohn worked in the field of transportation engineering, applying his knowledge of vision science to solve practical problems. With his understanding of the way the eye detects visual signals and passes that information to the brain, he was able to develop new warning systems that allow people to react faster. In the late 1990s, Cohn was asked by the California Department of Transportation (Caltrans) to test the effectiveness of LEDs in traffic lights. When he and his laboratory team used large-field flicker photometry to show that diodes were at least as effective visually as standard incandescent lamps, something that one could not conclude with certainty from simple photometry measurements, Caltrans began switching to diodes in traffic signals across the state, resulting in huge energy savings.

 

Other inventions from his laboratory were a cone-shaped emergency warning light for highway work vehicles and a light bar that indicates when a vehicle is braking, both designed to take maximum advantage of the eye’s sensitivity to motion. Before he died, Professor Cohn was investigating methods of making railroad crossings safer.

 

From the beginning of his career, Ted Cohn stood out at Berkeley. Like his peers, he was talented and possessed of powerful drive and intense focus. Yet he did not pursue his research to the exclusion of all else. Ted was first and foremost a good citizen, contributing to the greater cause. He accepted committee assignments that many faculty members prefer to avoid. He was always available to meet with undergraduate, professional and graduate students, and to assist them in any way he could. He devised ways to open opportunities to disadvantaged students and initiated, long before it became policy in some institutions, a process to allow high school students to spend summers in his laboratory, to encourage them on the path toward higher education.

 

Professor Cohn’s career as a teacher goes beyond a mere summary of standard courses in vision science. His teaching plan involved getting everyone involved in the process. He initiated the peer mentoring scheme where graduate students mentored the undergraduates in bioengineering. He initiated a much appreciated course on how to teach and be successful at it. One of his former students has recalled, “Dr. Cohn brought life to the world of visual perception for me. He was also someone who lifted you up to see yourself in a magnificent way. He was a great teacher and person.”

 

Professor Cohn had an admirable record of advancing programs in higher education, including his leadership in bioengineering, where he served as a committed vice chair for graduate affairs in the department and chaired the executive committee of the UC Berkeley/UC San Francisco Joint Graduate Group. The bioengineering graduate program grew tremendously during his tenure, and his leadership and advocacy were essential ingredients in the program’s successful transition. As professor of vision science, he managed the tedious details of the building remodeling program for Minor Hall on the Berkeley campus during the School of Optometry’s 1992 move. Ted was an uncommonly dedicated and effective campus leader.

 

Ted’s generosity extended to his colleagues. As he became a senior faculty member, Professor Cohn sought out new faculty to offer assistance in their early careers. Even in difficult times, Ted always maintained the most positive of attitudes. He interpreted events, and people’s actions and behaviors, in the most generous ways possible. He was firm, logical, and most of all courteous, when arguing a viewpoint that might differ substantially from a colleague’s. Altogether, Ted Cohn’s humane and supportive characteristics were outstanding in the academy and perhaps in the general human condition.

 

Professor Cohn is survived by his wife, Barbara A. Cohn, Ph.D., an epidemiologist with whom he collaborated; sons Avery S. Cohn and Harris S. Cohn, and daughter, Adrienne L. Cohn, all of Berkeley; brother David Cohn of Dobbs Ferry, New York; sisters Anne Cohn Donnelly of Winnetka, Illinois, Amy Cohn Tucker of White Plains, New York, and Julie Cohn Connor, of Houston, Texas; and mother, Marjorie Cohn Pfeffer, of Winnetka, Illinois.

 

We will miss Ted Cohn and remember his work and the future he strove to create.

 

 

Thomas F. Budinger

Stanley Klein

Dennis Levi

Sharmila Majumdar