Mammals

The common marmoset

The common marmoset, Callithrix jacchus, belongs to the Callitrichidae family (New World Monkeys). Endemic in the Northeast forest of Brazil, they have conspicuous large white ear tufts and an annulled tail that changes between black and grey bars. The weight of an adult common marmoset vary between 300 gm to 450 gm, and the average body measurement of an adult common marmoset are neck to tail base 25 cm, tail 28 cm. Common marmosets normally live in extended family groups varying in size between 5-15 individuals. Typically, groups contain only one breeding pair, the dominant male and its mate. The breeding female suppresses reproduction in the other adult females. Breeding females show a high reproductive rate resulting from a biannual twinning and postpartum ovulation.

Humans

Humans (Homo sapiens) are primates that have unusual cognitive abilities - we can communicate in an open-ended, flexible fashion using language (spoken, written or signed). Furthermore, humans have elaborate cultural traditions, with visual and musical creativity being a hallmark of human cultures around the world.

We are interested in the computational complexity of human language, using artificial grammars to model the learning process that may underlie the acquisition and development of syntax. We also study perceptual and productive mechanisms in the auditory and visual domain, with a focus on music and art as well as language. We use a comparative approach in all the research we do, that is, we always try to identify to what extent human cognitive abilities might be shared with other species.

Elephants

Elephants have the largest absolute brain size of any land animal and larger brains should provide greater information processing power. High metabolic cost of brain tissue, however, requires that animals only invest in large brains if they need to overcome some serious cognitive challenges. (Bates et al. 2008)

African and Asian elephants are long-lived, terrestrial mammals with a complex social organization. Although the multi-level structure differs between Asian and African elephants, both species exhibit fission-fusion dynamics, where individuals possess different levels of association, from ephemeral to close, long-term affiliates. Elephants are non-specialist browser and do not experience considerable pressure from natural predators due to their size. Thus, the elephants biggest cognitive challenges are most likely to be social.

Elephants are very communicative, and of special interest is the acoustic communication. Elephants communicate using low-frequency vocalizations, and due to their complex social structure, seem to have an extensive network of vocal recognition (McComb et al. 2003). Elephants are capable of vocal learning (Poole et al. 2005, Stoeger et al. 2012), a cognitive trait, which among mammals, is only shared with humans, certain marine mammals and bats. This is an additional reason to study elephant vocal behaviour. In addition, elephants are more closely related to aardvarks and manatees, than to primates, and thus represent a vulnerable species for any comparative research approach.

At our department we study African savannah (Loxodonta africana) and Asian elephants (Elephas maximus) kept under human care (zoos and sanctuaries) combined with research on free-ranging elephants.