Summary: Great ape cognition is highly individualized, dynamic, and structurally distinct from human intelligence. Tracking 48 chimpanzees, bonobos, gorillas, and orangutans over 18 months, researchers determined that individual cognitive differences are stable over time and heavily dictated by rearing, sex, and social groups.
Crucially, while human social skills develop in cohesive clusters, an ape’s performance on distinct social tasks showed zero correlation, demonstrating that great apes possess an alternative cognitive architecture that challenges traditional, human-centric evolutionary models.
Key Facts
- Individual Profiles Over Species Averages: Great ape intelligence is not uniform within a species; individual apes possess unique, stable cognitive strengths and weaknesses that persist over time.
- 18-Month Longitudinal Tracking: The study monitored 48 individual primates across four distinct species (chimpanzees, bonobos, gorillas, and orangutans) using a repeat-testing framework over a year and a half.
- Key Performance Predictors: An individual ape’s cognitive performance is strongly predicted by environmental and demographic variables, including their specific social group, sex, rearing history, and past research experience.
- Departure from Human Brain Structure: Unlike humans, whose social cognitive abilities tend to develop symmetrically as a cohesive cluster, great apes showed zero statistical correlation between different social testing tasks.
- Call for Custom Primate Tools: Researchers emphasize that current psychological tests are heavily biased toward human cognitive structures, highlighting an urgent need to design assessment tools tailored specifically to ape biology.
Source: APS
For decades, scientists have been studying the cognition of great apes to understand how our own complex cognitive abilities evolved. Much of the research is based on the idea that if a particular ability—like using gestures to communicate—is found only in species that are closely related to us, then it’s likely that the trait appeared relatively late in our evolutionary history.
But these interpretations see cognition as static—and uniform within a particular species. In reality, great apes, like humans, have cognitive abilities that develop, wax, and wane throughout their lifetimes. These abilities also likely vary between individual apes as different personalities and life experiences shape cognitive ability.
“There’s a lot of experiences that … contribute to the precise nature of how [an individual’s] cognition is structured and organized,” said Manuel Bohn, a developmental psychologist at Leuphana University of Lüneburg. “We very much have these kind of developmental and individual differences perspectives for humans. And so, we thought this was clearly missing in great apes.”
In a new study published in Psychological Science, which builds upon a 2023 study by Bohn and his colleagues, researchers assessed how a range of cognitive abilities differed between individual great apes over an extended period of time.
The research not only found that cognition consistently varied between individuals, it also revealed just how much researchers have yet to understand about the fundamental structure of great ape cognition.
To gain these conclusions, Bohn and colleagues studied 48 individual great apes. This sample comprised four species, ranging in age and sex: bonobos, chimpanzees, gorillas, and orangutans. The apes participated in a series of six cognitive tests over a period of a year and a half, including tasks like seeing if apes could follow the attention of a human experimenter, understand communicative cues, and remember where they searched for food.
These tasks were based on past procedures that comparative psychologists have used in research to test for social cognition, reasoning, and executive function in great apes.
The study found that there was a substantial amount of variation between individual apes, even among the same species. Variables like what group an ape belongs to, its previous experience with research, sex, and rearing were strong predictors of performance. In addition, these individual differences in cognitive performance were relatively stable over the course of the study for most tasks.
“That’s also often the way that we think about individual differences in humans, like they are stable traits or some property of an individual. And we find pretty good evidence that this is the case here in great apes as well,” Bohn said.
Researchers also analyzed how performance on various tasks correlated with one another to understand how parts of ape cognition are related and structured. Interestingly, the results from tasks that relied on social cues (i.e., attention following) were not correlated with one another; high performance on one did not mean high performance on another. By contrast, most results from tasks that were nonsocial (i.e., reasoning) were solidly correlated.
This deviates from the cognitive structure that we know of in humans. “We do not find these clusters that we expect to be there from a human perspective, which I think is really interesting and thought-provoking,” Bohn said. “If it’s not this, then what is the structure of all of this?”
Bohn emphasized that though the sample size of the new research is small, it opens up questions that researchers could continue to investigate. He noted that future research could more rigorously assess the tools that researchers use to measure great ape cognition and seek to understand whether these tools are measuring the appropriate parts of cognition.
“We don’t have assessment tools that have been particularly built to assess the different aspects of great ape cognition,” Bohn said.
He also noted the need for longitudinal studies, although he acknowledged that these studies are often difficult to execute. But taking on the challenge could allow scientists to track and document cognitive development and how developmental progress varies between individuals. By comparing these findings with human development, it may be possible to understand the drivers behind great ape cognition and how it varies from our own.
“Think about these alternative structures of cognition,” Bohn said. “What are the lines along which we can think about cognition being structured, other than the ones that we put in place for humans? [This study] is an invitation to think along those lines.”
Key Questions Answered:
A: Just like humans, individual apes have unique personalities, distinct genetic backgrounds, and varied life experiences that continuously sculpt their neural pathways. Treating an entire species as having a single, fixed level of intelligence ignores how cognitive abilities naturally develop, peak, and change across a lifetime. Factoring in individual differences reveals that an ape’s intelligence is a dynamic, living system rather than a fixed evolutionary snapshot.
A: In human developmental psychology, social skills generally pull in the same direction—if a child is excellent at reading communicative cues, they are usually statistically likely to excel at following attention. In great apes, this link completely vanished. An ape could be exceptional at tracking an experimenter’s gaze but fail entirely at interpreting a direct communicative gesture. This proves that ape social cognition is structured on completely different evolutionary lines than our own.
A: The primary obstacle is sample size and the acute shortage of customized testing equipment. Longitudinal studies tracking primates over long periods are exceptionally difficult to execute. Furthermore, almost all current comparative psychology tools were originally built to measure human milestones. To truly understand ape cognition, scientists must build new, non-anthropocentric assessment tools that measure the mind on the ape’s own evolutionary terms.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this social and evolutionary neuroscience research news
Author: Hannah Brown
Source: APS
Contact: Hannah Brown – APS
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Individual Differences in Great Ape Cognition Across Time and Domains: Stability, Structure, and Predictability” by Bohn, M., Völter, C. J., Hanus. D., Eisbrenner, N., Eckert, J., Holtmann, J., & Haun, D. Psychological Science
DOI:10.1177/09567976261434817
Abstract
Individual Differences in Great Ape Cognition Across Time and Domains: Stability, Structure, and Predictability
Understanding variation in cognitive abilities is critical to understanding both the evolution and development of cognition. In this study, we examined the stability, structure, and predictability of individual differences in cognitive abilities in great apes across a broad range of domains, including social cognition, reasoning about quantities, executive function, and inferential reasoning.
We administered six tasks to 48 individuals from four species, spanning 10 sessions over 1.5 years. Task performance was most strongly predicted by stable, individual-specific characteristics rather than transient or group-level variables. Using additional data from the same individuals in other tasks, we found substantial positive correlations between nonsocial tasks. In contrast, tasks measuring social cognition were not correlated either with each other or with nonsocial measures.
Future studies should work toward mechanistic models of great apes’ cognitive processes to build an understanding of the evolution of cognition based on process-level commonalities across species.
