Robert R. Capranica

Excerpt from letter written by ER Lewis in 2004

When they published their landmark work-- "Comparative Hearing: Fish and Amphibians" in 1998, RR Fay and AN Popper dedicated the volume to two hearing researchers-- Robert R. Capranica (amphibians) and William N. Tavolga (fish). This was a thoroughly fitting tribute to two pioneers in bioacoustics.

Bob Capranica's entry to the field occurred 35 years earlier. In the late 1950's and early 1960's Lettvin and Maturana gave the world a new perspective on vision when they carried out neurophysiological studies that suggested that signal-processing in the frog 's eye may be directly related to the frog's behavior (see "What the frog's eye tells the frog's brain," Proc. I.R.E. 47: 1940-1951). At nearly the same time, Frishkopf and Goldstein were carrying out neurophysiological studies on the frog's ear- discovering three broad classes of primary auditory afferent fiber. Two of these classes were attributable to one auditory sensor-- the amphibian papilla, the third class was attributable to another sensor, the basilar papilla. At this point, Bob Capranica entered the picture. He decided that if one really wished to link behavior directly to neurophysiology, he would have to examine the behavior at least as carefully as he examined the neurophysiology. He used the American bullfrog as his animal subject and evoked calls as his behavioral assay. He carefully categorized the animal's vocalizations (e.g., advertisement call, territorial call, warning call, distress call) and dissected each of them spectrographically (see RR Capranica, "The vocal repertoire of the bullfrog," Behaviour 31: 302-325, 1968). He showed that each acoustic element of each vocalization excited a specific subset of the three classes of bullfrog auditory fibers. This was followed by his demonstration, with natural and synthetic stimuli, that there was a direct mapping from excited subset to behavioral response (see RR Capranica, "Vocal response of the bullfrog to natural and synthetic mating calls," J. Acoust. Soc. Am. 40: 1131-1139, 1966). When the behavioral results were thoroughly integrated with the neurophysiology, they brought astounding new clarity to our understanding of amphibian audition. The resulting paper (LS Frishkopf, RR Capranica, MH Goldstein Jr, "Neural coding in the bullfrog's auditory system-- a teleological approach," Proc. I.E.E.E 56:969-980, 1968) stands as a pioneering classic in the field of neuroethology. It took a bold step beyond the Lettvin-Maturana approach, and it established Bob Capranica as a founding father of that field. Subsequent generations of researchers in neuroethology have, directly or indirectly, modeled their paradigms on his.

When he left his physiological collaborators in the late 1960s, and took a position at Cornell, Bob, of necessity, became more directly involved in the physiological side of frog hearing-- integrating it carefully with his continuing behavioral work, both in the lab and in the field. For the next twenty years, he and his graduate students and postdocs extended the neuroethological studies to a full evolutionary spectrum of frog species. Bob pioneered studies in the roles of advertisement calls and hearing in speciation, examining geographical covariations of call dialects and peripheral tuning in single species. Having shown, in his earlier work, the importance temporal structure (in addition to spectral structure) in bullfrog vocalizations, he pioneered studies of temporal signal processing at the frog's auditory periphery and in the frog's brainstem and midbrain. In the mid 1970s Bob was selected to follow Donald Kennedy as the American editor of the Journal of Comparative Physiology A, the premier neuroethology journal. Bob's former students and postdocs now compose the Who's Who of frog bioacoustics. Furthermore, although there are a few of us who have worked on frog bioacoustics who were not students or postdocs of Bob, there are none of us who were not profoundly influenced by his work; and most of us were influenced by him directly-- through collaboration of one sort or another. For myself, it was Bob's pioneering work that initially attracted me to the frog's ear, and it was that work that provided the platform on which my own research was built.

I feel no hesitation in saying two things: (1) our understanding of frog bioacoustics has made huge advances since the publication in 1968 of "... a teleological approach," and (2) Bob is the well from which that understanding has sprung. It is no accident that one of his former graduate students is the current American editor for the Journal of Comparative Physiology A (now the official journal of the International Society for Neuroethology) and another of his former graduate students is the current president of that Society.

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