Memory for individuals: Hamsters (Mesocricetus auratus) require contact to develop multicomponent representations (concepts) of others.

Abstract

In humans, individuals recognize other individuals by numerous types of independent information, such as the quality of the voice, appearance of the face, smell, gait, and posture. Humans also have integrated memories of others--that is, in response to a face or a voice the individual is recognized by name and other information about that individual is remembered. In many nonhuman species, individual recognition also occurs. Although observational studies suggest that individuals of some nonhuman species may be able to use several different cues for individual recognition, little experimental proof for this is available. Golden hamsters have at least 5 individually distinctive odors and they develop integrated, multi-odor memories (concepts) of familiar individuals, as shown by across-odor habituation experiments. Little is known, however, about the conditions that are necessary to develop such integrated memories. In these experiments we investigated what kinds of experiences were necessary for male hamsters to develop multiodor memories of females. The results show that exposure to all of the odors of another individual was not sufficient to develop such multiodor memories but that physical contact between the subjects and stimulus animals was necessary. Multiodor representations were developed after interactions with anesthetized individuals, confirming the finding that physical contact was important but also showing that interaction with an awake, behaving individual was not necessary to form multiodor representations of other individuals. We are not aware of experimental proof for integrated, multicomponant memories in any other nonhuman species.

Cross-modal individual recognition in domestic horses ( Equus caballus )

“…Nonhuman primates can process audiovisual information cross-modally to match indexical cues (20) and number of vocalizers (21), to match and tally quantity across senses (22) and associate the sound of different call types with images of conspecifics and heterospecifics producing these calls (23)(24)(25). Research aimed specifically at investigating the categorization of individuals has shown that hamsters (Mesocricetus auratus) are capable of matching multiple scent cues to the same individual (26) and that certain highly enculturated chimps (Pan troglodytes) can, through intensive training, learn to associate calls from known individuals with images of those individuals (27)(28)(29). Some species have also been shown to spontaneously integrate auditory and visual identity cues from their one highly familiar human caretaker during interspecific, lab-based trials (30,31).…”

Seeing who we hear and hearing who we see

“…Hamsters, they suggest, have an integrated, multiodor memory of other individuals. Recent experiments indicate that direct physical contact with an individual-not just exposure to its odors-is necessary for such memories to develop (12).…”

Cross-modal individual recognition in wild African lions

“…However, while individual recognition is thought to be a widespread ability [3], providing robust scientific support for recognition at the level of the individual has proved difficult [4,5]. 'True' individual recognition strictly constitutes the identification of a specific individual, according to individually distinct cues, and the placement of that individual within a society of many others [6].…”