Physiological Observations on
Sam H. Ridgway Naval Ocean Systems Center, San Diego
Physiological observations can possibly contribute to the understanding of cognition from at least three approaches. First, understanding of biological phenomena often results from correlation of apparently unrelated findings in anatomy, behavioral science, and physiology. Therefore, it seems appropriate to present some findings on the physiology of the dolphin brain in a conference on dolphin cognition and behavior. Second, because our best examples of mental events rest in our own conscious experiences, similarities of brain structure and function between animals and human adults have been suggested as a possible basis for inferring mental process ( Neville & Hillyard, 1982). Third, mental processes must occur within the nervous system and there cause some change. If such changes are measurable, we might be able to assess the dolphin's cognitive ability. These processes, however, are difficult to measure because so much goes on within the nervous system that is not necessarily either conscious, mental, or cognitive--e.g., the regulation of body functions (breathing, circulation, homeostasis), proprioceptive adjustments (posture, balance, orientation), sensory coordination and involuntary reflexes, to name a few. Recently, methods have been devised for measuring "event related potentials" (ERP) from the human brain. Some averaged waves recorded from the scalp such as the "P300" and "N400" appear to be associated with cognition ( Callaway, Tueting, & Koslow, 1978; Kutas & Hillyard, 1980). Work on dolphin ERP is discussed in another chapter ( Woods, Ridgway, Carder, & Bullock).
Physiological methods such as the ERP offer potential as a nonbehavioral means of investigating animal cognition that may be especially valuable if the ERP can be correlated with behavior. Although it has been asserted that cognitive characteristics can only be measured through behavioral experiments and