Testing marine mammal hearing with a vocal response paradigm and the method of free response

Abstract

Behavioral hearing tests with marine mammals often use single interval experiments with a go/no-go paradigm, where the subject pushes a response paddle or similar device to indicate the presence of a hearing test tone. This approach is widely accepted, but the time required for the subject to physically move and/or interact with the response device and the requirement of one trial per reinforcement interval limit the speed at which data can be collected (typically 20–30 minutes for a threshold). An alternative to the single interval/paddle press approach is the use of a vocal response technique and the method of free response, where multiple trials are presented within a single reinforcement interval. An acoustic or vocal response eliminates the need for the subjects to physically move, allowing for faster responses and shorter inter-trial intervals. The method of free response allows multiple tone presentations between reinforcement periods, dramatically increasing the rate at which data may be collected, especially from diving marine mammals. This talk describes the application of these techniques to hearing tests of bottlenose dolphins, white whales, and California sea lions and the advantages and disadvantages compared to the single interval experiment. [Work supported by ONR.]