The common marmoset (Callithrix jacchus), a highly vocal New World primate species, has emerged in recent years as a promising animal model for studying brain mechanisms underlying perception, vocal production, and cognition. The present study provides a quantitative acoustic analysis of a large number of vocalizations produced by marmosets in a social environment within a captive colony. Previous classifications of the marmoset vocal repertoire were mostly based on qualitative observations. In the present study a variety of vocalizations from individually identified marmosets were sampled and multiple acoustic features of each type of vocalization were measured. Results show that marmosets have a complex vocal repertoire in captivity that consists of multiple vocalization types, including both simple calls and compound calls composed of sequences of simple calls. A detailed quantification of the vocal repertoire of the marmoset can serve as a solid basis for studying the behavioral significance of their vocalizations and is essential for carrying out studies that investigate such properties as perceptual boundaries between call types and among individual callers as well as neural coding mechanisms for vocalizations. It can also serve as the basis for evaluating abnormal vocal behaviors resulting from diseases or genetic manipulations.

The common marmoset is a small, arboreal, New World primate that has emerged as a promising non-human model system in auditory neuroscience. A complete understanding of the neuroethology of auditory processing in marmosets will include behavioral work examining how sounds are perceived by these animals. However, there have been few studies of the marmoset's hearing and perceptual abilities and the audiogram of this species has not been measured using modern psychophysical methods. The present experiment pairs psychophysics with an operant conditioning technique to examine perception of pure tone stimuli by marmosets using an active behavioral paradigm. Subjects were trained to lick at a feeding tube when they detected a sound. Correct responses provided access to a food reward. Pure tones of varying intensities were presented to subjects using the method of constant stimuli. Behavioral thresholds were calculated for each animal based on hit rate -threshold was defined by the tone intensity that the animal correctly identified 50% of the time. Results show that marmoset hearing is comparable to that of other New World monkeys, with a hearing range extending from about 125 Hz up to 36 kHz and a sensitivity peak around 7 kHz.

The common marmoset (Callithrix jacchus) is a small New World primate that has increasingly been used as a non-human model in the fields of sensory, motor, and cognitive neuroscience. However, little knowledge exists regarding behavioral methods in this species. Developing an understanding of the neural basis of perception and cognition in an animal model requires measurement of both brain activity and behavior. Here we describe an operant conditioning behavioral training method developed to allow controlled psychoacoustic measurements in marmosets. We demonstrate that marmosets can be trained to consistently perform a Go/No-Go auditory task in which a subject licks at a feeding tube when it detects a sound. Correct responses result in delivery of a food reward. Crucially, this operant conditioning task generates little body movement and is well suited for pairing behavior with single-unit electrophysiology. Successful implementation of an operant conditioning behavior opens the door to a wide range of new studies in the field of auditory neuroscience using the marmoset as a model system.