Primate brain size does not predict their intelligence
Scientists from Go"ttingen compare cognitive skills of different primate species

Date:
September 25, 2020
Source:
Deutsches Primatenzentrum (DPZ)/German Primate Center
Summary:
A research team has systematically investigated the cognitive
abilities of lemurs, which have relatively small brains compared
to other primates.

Conducting systematic tests with identical methods revealed that
cognitive abilities of lemurs hardly differ from those of monkeys
and great apes. Instead, this study revealed that the relationship
between brain size and cognitive abilities cannot be generalized
and it provides new insights into the evolution of primates.



FULL STORY ========================================================================== Chimpanzees, gorillas and orangutans are our closest relatives, and like
us they have relatively large brains and they are very intelligent. But
do animals with larger brains really perform better in cognitive tests? A research team from the German Primate Center (DPZ) -- Leibniz Institute
for Primate Research in Go"ttingen has for the first time systematically investigated the cognitive abilities of lemurs, which have relatively
small brains compared to other primates. Conducting systematic tests
with identical methods revealed that cognitive abilities of lemurs hardly differ from those of monkeys and great apes. Instead, this study revealed
that the relationship between brain size and cognitive abilities cannot be generalized and it provides new insights into the evolution of cognitive abilities in primates.


========================================================================== Humans and non-human primates are among the most intelligent living
beings.

Their brain size may underly their intelligence as primates have
relatively large brains in relation to their body size. For example, it
is assumed that larger brains enable faster learning and better memory capacities. Within primates, however, species can differ up to 200-fold
in brain size. A team of researchers from the German Primate Center (DPZ)
has now investigated whether the cognitive performances of lemurs with
their relatively small brains differ from those of other primates.

Using a comprehensive standardized test series of cognitive experiments,
the so-called "Primate Cognition Test Battery" (PCTB), small children,
great apes as well as baboons and macaques have already been tested for
their cognitive abilities in the physical and social domain. Cognitive
skills in the physical domain include the understanding of spatial,
numerical and causal relationships between inanimate objects, while
cognitive skills in the social domain deal with intentional actions, perceptions and the understanding of the knowledge of other living
beings. Initial studies have shown that children possess a better social intelligence than non-human primates. In the physical domain, however,
the species hardly differed even though they show great variation in
their relative brain sizes.

For the first time, researchers of the "Behavioral Ecology and
Sociobiology Unit" of the DPZ have now tested three lemur species with
the PCTB. Lemurs are the most basal living primates and represent the evolutionary link between primates and other mammals, which is why they
serve as a living model of primates' origin of cognitive abilities. The
study examined ring-tailed lemurs, black-and-white ruffed lemurs and grey
mouse lemurs, which differ in their social system, diet and brain size,
not only among each other, but also compared to the previously tested
Old World monkeys and great apes.

The results of the new study show that despite their smaller brains
lemurs' average cognitive performance in the tests of the PCTB was
not fundamentally different from the performances of the other primate
species. This is even true for mouse lemurs, which have brains about 200
times smaller than those of chimpanzees and orangutans. Only in tests
examining spatial reasoning primate species with larger brains performed better. However, no systematic differences in species performances were
neither found for the understanding of causal and numerical relationships
nor in tests of the social domain. Neither diet, nor social system or
brain size could explain the results from the PCTB experiments. "With our
study we show that cognitive abilities cannot be generalized, but that
species instead differ in domain-specific cognitive skills," says Claudia Fichtel, one of the two first authors of the study funded by the German Research Foundation. "Accordingly, the relationship between brain size
and cognitive abilities cannot be generalized." The study represents the
first systematic and comparative investigation of cognitive abilities in
lemurs and provides important insights into the evolution of cognitive abilities in primates. However, the research team also emphasizes that
further comparative studies in a variety of other species are essential
to answer the many questions about the relationship between brain size,
diet, social life and cognition.


========================================================================== Story Source: Materials provided by Deutsches_Primatenzentrum_(DPZ)/German_Primate_Center.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Claudia Fichtel, Klara Dinter, Peter M. Kappeler. The lemur
baseline: how
lemurs compare to monkeys and apes in the Primate Cognition Test
Battery.

PeerJ, 2020; 8: e10025 DOI: 10.7717/peerj.10025 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200925113353.htm

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