Physiology& Behavior. Vol. 53, pp. 89-95, 1993 0031-9384/93 $6.00+ .00 Printedin the USA. Copyright© 1993PergamonPressLtd. Assessing Olfactory Performance in a New World Primate, Saimiri sciureus MATTHIAS LASKA ~ AND ROBYN HUDSON Institut fiir Medizinische Psychologie, Ludwig-Maximilians-Universitdt, Goethestr. 31, D-8000 Miinchen 2, Germany Received 1 June 1992 LASKA, M. AND R. HUDSON. Assessing olfactoryperformance in a New World primate, Saimiri sciureus. PHYSIOL BEHAV 53(1) 89-95, 1993.--Using a task designed to simulate olfactory-guidedforagingbehavior, this study demonstrates .for the first time that olfactory performance can be reliably assessed in squirrel monkeys. Small flip-top vials were fixed in random order to the arms of a climbing frame and equipped with odorized strips signallingeither that they contained a peanut food reward (S+) or that they did not (S-), and three adult female monkeys were allowed 1 min to harvest as many baited nuts from this tree as possible. Given five l-min trials per day, animals took between 15 and 25 days to reach the criterion of 80% correct choices, could readily transfer to new S+ or S- stimuli, and could remember the task even after a l-month break. The precision and consistency of the monkeys' performance in tests of discrimination ability and sensitivity demonstrate the suitability of this paradigm for assessingolfactory function, and a first test of human subjects using the same cups and odorants showed that it may also be used to directly compare olfactory performance in human and nonhuman primates. Squirrel monkeys Odor learning Olfactory performance Behavioral testing Human subjects PRIMATES are typically regarded as visual animals and it is, therefore, hardly surprising that investigations of primate sensory perception and processing should have concentrated on this modality. Although considerable attention has also been given to acoustic and somatosensory function, olfaction has been tra- ditionally considered of only minor importance. However, it is becoming increasingly clear from studies of both human and nonhuman primates that olfaction may, in fact, play a significant part in the regulation of a wide variety of primate behaviors. In addition to its more obvious role in food identification and selection, there is now evidence from a number of species for olfactory involvement in social behaviors such as the estab- lishment and maintenance of rank (4), territorial defence (16), identification of sexual partners (14,17), and recognition of group members (7). This is particularly true for the prosimians and New World monkeys, many of which possess odor-producing skin glands (6) and demonstrate conspicuous marking behaviors (5). In the squirrel monkey, Saimiri sciureus, for example, hand- washing with urine (3), nasal rubbing and sneezing (22), back rubbing (9), and anogenital inspection (19) all appear to be as- sociated with olfactory communication, and olfactory recogni- tion of mothers by infants has also been demonstrated (13). Despite such observations, there have been few systematic studies of olfactory-guided behavior in nonhuman primates, and to our knowledge, no investigations at all of olfactory perfor- mance using psychophysical procedures. However, if we wish to understand olfactory function and appreciate the role odor cues may play in regulating a species' behavior, it is necessary to have a knowledge of the animals' basic perceptual capacities. It was, therefore, our aim in this study to develop a means of reliably assessing olfactory performance in a primate. Squirrel monkeys were chosen because of their broad repertoire of ol- factory-mediated behaviors, and the considerable information available on their visual and acoustic capabilities (2,12,20), cog- nitive performance (8), and social behavior (1,10). In this study we demonstrate for the first time that by using an ethologically based behavioral test, olfactory threshold and discrimination ability can be accurately and reproducibly de- termined in squirrel monkeys. We also present data from human subjects tested on the same tasks demonstrating the performance of the two species to be similar. METHODS Animals Testing was carried out using three adult female squirrel monkeys maintained as part of an established breeding colony of 13 animals; one adult male, six adult females, and six juveniles. The colony was housed in a double enclosure comprising a 23 m 3 home cage joined to a 7 m 3 test cage by two tunnels which could be closed by sliding doors to allow the temporary sepa- ration of animals for individual testing. Animals were fed mar- moset pellets (Altromin®) and fresh fruit and vegetables ad lib. ' Request for reprints should be addressed to Dr. Matthias Laska. 89