Gerald H. Jacobs, Distinguished Professor Emeritus at UCSB, passed away in Santa Barbara on October 15, 2025, after a year-long illness. Jerry was a renowned scientist, educator, and mentor, dedicating his life to unraveling the complexities of color vision across the animal kingdom and in elucidating the underpinnings of color blindness. His meticulous research, employing psychophysical, physiological and genetic approaches, rendered him an expert in comparative color vision, garnering international recognition. His legacy is cemented not only through this extensive body of work and the lucidity in his writing, but also through the inspiration he engendered in his students and colleagues, and the enduring impact of his discoveries. Those who knew him will remember him especially for his particular sense of humor.
Jerry was born in 1934, growing up in Wilmington, Vermont. He attended the University of Vermont, majoring in Psychology and Zoology, graduating in 1956. Following military service, he attended Indiana University working in the laboratory of Russell DeValois, completing his PhD in Physiological Psychology in 1963. He was appointed as an Assistant Professor in 1964 at the University of Texas at Austin. He advanced to Associate Professor there, and remained until 1969, when he was recruited to the Department of Psychology at UCSB, where he had remained for the entirety of his subsequent career. He was one of the original founding faculty members of the Neuroscience Research Institute, and subsequently relocated his laboratory space from Psychology to the NRI, a short walk across campus in the Biological Sciences II building.
Jerry’s thesis work set the stage for a theme he pursued through much of his career. That early work demonstrated that the behavior of single cells within the monkey brain code exquisitely for the primary color-opponent axes, red-green and blue-yellow, and predict rather well behavioral performance on various psychophysical tests of color vision ability. Interestingly, different species of monkey (squirrel monkeys versus macaque monkeys) displayed marked differences in their color vision ability and in the behavior of single cells within the brain. The roots of this distinction, and the even more surprising discovery that with the population of squirrel monkeys, there was marked variation in their color vision abilities, provided ample ground for further exploration in the decades to come.
Within the population of squirrel monkeys, Jerry discovered that all males were dichromats, showing red-green color blindness, whereas females were either dichromats or trichromats, evinced both behaviorally and by recording the electrical response of the retina to identify the spectral sensitivities of the photopigments within the cone photoreceptors of the eye. By contrast, old world primates like humans exhibit congenital red-green color-blindness only rarely. Subsequent studies across a large number of old versus new world primate species largely confirmed this generality (with a few notable exceptions), ultimately providing a genetic understanding for the distinctive X chromosome-linked inheritance patterns of red-green color blindness, and implicating distinct evolutionary paths to trichromacy, summarized nicely in a Scientific American article in 2009 by Jerry and his colleague Jeremy Nathans, from Johns Hopkins University.
Within the two groups of dichromats and trichromats among the population of squirrel monkeys, Jerry identified a polymorphism within each group, suggesting distinct genetic variants (alleles) coding for the spectral tuning of each photopigment. Working with Maureen and Jay Neitz at UCSB, Jerry went on to identify those genetic sequence variants, elucidating this uniqueness of most new world primates: one of three different alleles determines the positioning of the spectral absorbance function along the medium-to-long wavelength portion of the spectrum, occupying a single locus on the X chromosome. Some fortunate females acquire different alleles on their two X chromosomes to render them trichromatic, providing their ability to discriminate between wavelengths of light in the red-to-green portion of the visible spectrum.
Jerry and his lab characterized the cone photoreceptor complements underlying the variety of color vision abilities in the eyes of a wide range of species, including a considerable population of UCSB undergraduates, other non-primate mammals including orders as varied as cetaceans, ungulates and rodents, with occasional forays outside mammalia to assess sea turtles, snakes and owls. Many of these studies required extensive trips by Jerry and his lab to visit zoos, animal preserves and marine parks. Using these non-invasive techniques, even some pet dogs were assessed.
One entirely unexpected finding was the discovery that the short wavelength-sensitive photopigment present in the mouse retina is actually tuned to ultraviolet light, providing vision in that portion of the spectrum invisible to most other mammals.
Mice, like nearly all other non-primate mammals, are dichromats, due to the presence of only two photopigment genes. Working again with Jeremy Nathans, Jerry showed that by adding the human long wavelength-sensitive photopigment gene in a transgenic mouse model, these mice could be rendered trichromatic, making color discriminations between red and green lights that no normal mouse could perceive.
These are but a few of his contributions to our understanding of color vision. His book, Comparative Color Vision, published in 1981, spelled out the difficulties in assessing color vision ability behaviorally in non-human species, requiring stringent control over variation in brightness independent of spectral composition. He published in excess of 200 scientific research articles and reviews, many in Science, Nature, and the Proceedings of the National Academy. His scientific contributions have been recognized both locally at UCSB, and internationally.
In 1996, Jerry was awarded the UCSB Faculty Research Lectureship, being the loftiest honor bestowed upon a faculty member by his university peers. In 1988, he was awarded the Rank Prize in Opto-Electronics, an international prize shared with John Mollon at Cambridge University and Jim Bowmaker at the Institute of Ophthalmology in London, for their demonstration that the polymorphic color vision abilities of squirrel monkeys could be traced to the spectral absorbance functions of individual cone photoreceptors measured using microspectrophotometry. In 1998, Jerry was awarded the Proctor Medal, presented by the Association for Research in Vision and Ophthalmology at its annual meeting in recognition of his outstanding research contributions in our understanding vision. In 2009, he was awarded the Verriest Medal by the International Colour Vision Society for his lifetime achievements in understanding color vision. And in 2012, he was given the Tillyer Award from the Optical Society of America, acknowledging his distinguished contributions to the science of vision. Finally, in 2022, he was given the Richard C. Atkinson Lifetime Achievement Award from his alma mater, Indiana University, in recognition of his lasting impact upon the field of vision research.
He was a Fellow of the Optical Society of America and of the American Association for the Advancement of Science, an Honorary Fellow of the International Colour Vision Society, and an Emeritus Fellow of the Association for Research in Vision and Ophthalmology.
Jerry retired from his teaching professorship in 2006, but offered freshman seminars thereafter, and continued as a Research Professor until he closed his lab in 2011. He and a former alumnus of the department, Dr. Steve Foote, together launched the Endowment for Psychological & Brain Sciences Fund in 2021, and Jerry made generous additional donations to the Neuroscience and Behavior Graduate Training Program. Jerry was an avid runner, carefully guarding his time during the lunch hour to go for a run well beyond the limits of campus, competing in shorter races and traveling for the occasional marathon over the years, his last race at the age of 80. Jerry and his wife, Chris Allen (herself a long-standing and cherished staff member on campus, being a former MSO in Sociology), together enjoyed traveling the world for invited lectures and conferencing, and later in retirement on cruises to various locations around the globe. He is survived by Chris, alongside Chris’s brother David and his wife Amy.
