Cognition in Tamarins and Marmosets, Special Topic by Intern Audra

As much of primate cognitive research is conducted with the goal of determining the development of cognition in humans, a majority of the information available is regarding Old World Monkeys and Apes, as they are more closely related to humans. Because of this, there is a disparity in the amount of cognitive research conducted on New World monkeys, such as Marmosets and Tamarins, due to the unfounded assumption that these species are intrinsically more primitive because of their relatively small brain size. In fact, recent evidence has uncovered that Callitrichid species indeed advance cognitively, and actually possess and display a vast array of adaptive behaviors in response to environmental and social cues alike.

The advances observed in primate cognition are partially explained by the possession of hands, which allow grasping behaviors that permit a vaster range of food sources, and thus a larger repertoire of foraging behaviors. Not only does this involve the necessity of identifying and processing a wider variety of food types, but also the requirement of extracting food supplies from more complex sources, like cracking open nuts. Because of this reliance on varying food sources, more advanced spatial cognition is required in order to recall where these sources are found. According to field studies, food supplies are not found in the wild by chance, but rather by direct routes taken from one source to the next. This information indicates that these monkeys must possess a complex mental representation of their forest habitat in order to forage so efficiently. 

Studies have also shown that Marmosets and Tamarins show advanced cognitive capacities in their ability to display object permanence–the awareness that an object continues to exist despite being out of sight. This is an ability that human children begin to develop at about six months of age. One study conducted on Tamarins found that in a situation involving brief exposure to tasks and foraging opportunities, Tamarins readily expressed the ability to track objects' movements and respond flexibly. In another study, Marmosets were able to locate food rewards which they watched being hidden under various objects, even when these objects were relocated. This ability to display object permanence is just another reminder that while they may not have the same cognitive functioning as humans, there are so many minute ways in which we are cognitively similar.

Social pressures are also thought to play a large role in the advances seen in primate cognition. Not only does the cooperation learned from working within and between groups to find food permit a higher abundance of resources, but it also allows a higher scale of protection to be afforded against predators. This is particularly common among Callitrichids, who are seen to have a uniquely high aptitude for cooperation. Many other primates commonly exhibit regular food aggression toward group members and outsiders, however, Callitrichids do not display these behaviors commonly. Furthermore, as there are generally only two breeding individuals in a group, the other group members are able to help in rearing the offspring. This is another uncommon behavior exhibited by Callitrichids that characterizes their high levels of cooperation, and thus, the vast intricacies of their cognitive abilities. 

At PPS, it is no surprise to the caretakers that these individuals possess advanced cognitive abilities. Due to the garden and orchard maintained on site, the monkeys in our care experience seasonal changes in the foods provided to them, much like they would encounter in the wild. The individuals are seemingly able to recall food items, and appear to have memories of favored foods, as they are heard excitedly chirping upon being presented with a preferred item they haven’t had since the last time it was in season. Additionally, the monkeys sometimes seem somewhat perplexed and surprised when a familiar food item is presented in a manner they do not expect, such as receiving a frozen piece of banana on a sunny day. Caretakers at PPS are fortunate enough to be able to witness innumerable behaviors such as these every day, which serve as daily reminders as to how truly similar we are.

References:

·       Ford, S.M. The Smallest Anthropoids: The Marmoset/Callimico Radiation. New York: 

Springer Science, 2009.

·       Neiworth, J.J. ; Steinmark, E.; Basile, B. M.; Wonders, R.; Steely, F.; DeHart, C. A test of object 

permanence in new-world monkey species, cotton top tamarins (Saguinus oedipus). PubMed, 2003.

·       Rylands, A.B. Marmosets and Tamarins: Systematics, Behaviour, and Ecology. New 

York: Oxford University Press, 1993.

·       Strier, Karen B. Primate Behavioral Ecology. Upper Saddle River, N.J: Prentice Hall, 2011. 

·       Sussman, R.W. Primate Ecology and Social Structure. Pearson Custom Publishing, 2003.