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1. 1. Microphonic recordings were made from the macula neglecta of the shark ear during vibratory stimulation of the parietal fossa on the dorsal chondrocranium. 2. 2. It is shown that the most direct path for vibration to the inner ear is through this fossa and the associated posterior vertical canal. 3. 3. The macula neglecta is a sensitive vibrational detector and may possibly be involved in underwater sound detection.

Microphonic potentials were recorded from the ears of the goldfish during acoustic stimulation in a situation where sound pressure and particle displacement could be varied. Microphonic potentials from fishes with the swim bladder intact were proportional to sound pressure. After removal of the swim bladder, sound pressure sensitivity declined by 20-35 dB and the response was generated in proportion to particle displacement. The ear's sensitivity to direct vibration of the head increases at between -3 and -6 dB/octave between 70 and 1500 Hz and is not affected by the removal of the swim bladder. It is concluded that the peripheral auditory system of the goldfish may function as a pressure detector or as a displacement detector, depending upon the impedance of the applied signal.

The behavioral responses of goldfish to a variety of amplitude‐modulated (AM) acoustic signals were studied using a stimulus generalization paradigm in combination with a classical conditioning method. Measurements were thus allowed of the equivalence among various complex and simple signals in controlling the conditioned respiration response. The goldfish's conditioned response to AM signals were found to be controlled by carrier frequency, modulation depth, and to a lesser extent, by modulation frequency in the 40‐Hz range. On the other hand, pure‐tone frequency exerted minimal behavioral control for subjects conditioned to AM signals. Subjects conditioned to a 40‐Hz pure tone tended to generalize maximally to an AM signal having a 40‐Hz modulation rate. The results indicate the degree to which the goldfish can use much of the information present in complex periodic acoustic signals and suggest the existence of periodicity pitch in fish.

Auditory frequency generalization in the goldfish was studied at five points within the best hearing range through the use of classical respiratory conditioning. Each experimental group received single-stimulus conditioning sessions at one of five stimulus frequencies (100, 200, 400, 800, and 1600 Hz), and were subsequently tested for generalization at eight neighboring frequencies. All stimuli were presented 30 db above absolute threshold. Significant generalization decrements were found for all subjects. For the subjects conditioned in the range between 100 and 800 Hz, a nearly complete failure to generalize was found at one octave above and below the training frequency. The subjects conditioned at 1600 Hz produced relatively more flat gradients between 900 and 2000 Hz. The widths of the generalization gradients, expressed in Hz, increased as a power function of frequency with a slope greater than one.

1. 1. Saccular potentials were recorded from two locations in the endolymphatic system of the carp to sound stimulation. 2. 2. The frequency response function recorded from the sacculus is essentially identical with the behavioral function for the goldfish, confirming that the sacculus is the primary acoustic detector of the ostariophysine ear. 3. 3. Measurements of the non-linearities in the saccular potentials illustrate the complex organization of the saccular macula, and a possible mechanism for signal-to-noise improvement and frequency analyzing capability is suggested which is independent of a cochlear-like spatial analysis.

Four experiments were conducted on auditory sensitivity and discrimination of goldfish within the acoustic near field. Experiment I studies the effects of the near field on sound pressure thresholds. The sensitivity of goldfish in terms of sound pressure appeared to vary with distance from the sound source. Experiment II studied stimulus generalization and frequency discrimination within the near field. A generalization gradient was observed which indicated that goldfish can discriminate a frequency change as small as 12.5% without explicit differential training. Experiment III studied the effects of far field noise on near field thresholds. A masking effect was observed which appeared to be a negatively accelerated function of masker spectrum level. Experiment IV tested the ability of goldfish to localize a sound source within the near field. It was shown that goldfish could discriminate between right 45 degrees and left 45 degrees stimulus directions. Implications of the results of the four experiments are discussed.

The purpose of this critical review is to reevaluate the current experimental literature on fish audition based upon evaluation of structural, physiological and behavioral studies. The specific emphasis of the paper will be to (1) review the recent literature on the psychophysiology of hearing in fishes; (2) look at the subject of fish hearing from the standpoint of auditory mechanisms and their relationship to what is known about hearing in terrestrial vertebrates; and (3) emphasize some questions and areas of research which we feel require more investigation. Based on the data reviewed in the paper we have tentatively concluded that the teleost auditory system is well adapted as a temporal analyzer.

This report describes a simple technique and restraining device for investigating classically conditioned inhibition of respiration in the fish. The restraining device is seen as having wide applicability for investigations which necessitate the immobilization of the S.

Judgments of stimulus similarity between AM signals and other simple and complex tones were obtained from goldfish using a stimulus generalization paradigm in combination with a classical respiratory conditioning technique. Several groups of fish were conditioned in inhibit respiration upon the presentation of an AM signal (400 Hz modulated at 100% by 40 Hz), and subsequently tested for generalization to other signals differing in degree of complexity, carrier frequency (fc), and modulating frequency (fm). All stimuli were presented at approximately 30 dB above threshold. Obvious generalization decrements occurred to test signals differing in fc while no decrements occurred to test signals differing only in fm. For subjects trained to AM signals and tested with pure tones, little generalization occurred to any test frequency in the range including fc and fm. Thus, while there is a great perceptual difference between an AM signal and a pure tone at fc, the major sensation evoked in fish by these AM signals...