What Sets Humans Apart: The Unique Ability to Remember Order

The capacity for order that sets humans apart from other animals.

Sep 12, 2023

In the grand tapestry of cognitive abilities that distinguish humans from other species on Earth, our capacity to remember the order of information holds a pivotal place. This unique ability shapes our conversations, guides our everyday life, and underpins our educational pursuits. A recent study, featured in the journal PLoS ONE

, has shed light on this distinctive cognitive trait, suggesting that it may be a truly human phenomenon. Even our closest relatives, such as bonobos, appear to lack the capacity to learn and retain order in the same way we do.

Johan Lind, an associate professor in ethology and deputy director at the Center for Cultural Evolution, Stockholm University, emphasizes the significance of this research:

"The study contributes another piece of the puzzle to the question of how the mental abilities of humans and other animals differ, and why only humans speak languages, plan space travel, and have learned to exploit the earth so efficiently that we now pose a serious threat to countless other life forms."

Previous research at Stockholm University had proposed the sequence memory hypothesis, suggesting that only humans possess the ability to recognize and remember sequential information accurately. This capacity, it was theorized, served as a fundamental foundation for our unique cultural abilities. However, this hypothesis had yet to be tested on our closest relatives, the great apes. The recent experiments filled this gap by investigating the memory capabilities of bonobos, a species of great ape.

In a series of experiments, bonobos and humans were tested on their memory abilities, particularly in recognizing sequences. They were tasked with pressing computer screens to distinguish between short sequences, such as identifying whether a yellow square preceded a blue square or vice versa. The results were illuminating.

Vera Vinken, associated with Stockholm University and now a Ph.D. student at the Biosciences Institute, Newcastle University, reports,

"The study shows that bonobos forget that they have seen a blue square already five to 10 seconds after it has disappeared from the screen, and that they have great difficulty learning to distinguish the sequences blue-square-before-yellow-square from yellow-square-before-blue-square, even though they have been trained for thousands of trials."

In stark contrast, humans demonstrated an impressive ability to quickly learn and distinguish these short sequences. However, the exact mechanisms underlying how our closest relatives remember and utilize sequential information remain a topic for further exploration.

Magnus Enquist, professor emeritus and co-founder of the Center for Cultural Evolution, comments,

"We now know that our closest relatives do not share the same sequential mental abilities with humans. But even if the results indicate that their working memory works in principle in the same way as in rats and pigeons, no one has yet demonstrated this in practice."

These findings provide compelling support for the sequence memory hypothesis. They suggest that during the course of human prehistory, our ancestors developed a unique ability to remember and process sequences—a crucial mechanism underpinning various distinctively human phenomena, including language, planning abilities, and sequential thinking.

The study underscores the remarkable cognitive differences that separate humans from even our closest evolutionary relatives. Our ability to remember and utilize the order of information has played a pivotal role in shaping our species' unique cultural and intellectual achievements, highlighting the rich tapestry of human evolution and cognitive development.

Lind, J., Vinken, V., Jonsson, M., Ghirlanda, S., & Enquist, M. (2023). A test of memory for stimulus sequences in great apes. PloS One, 18(9), e0290546. https://doi.org/10.1371/journal.pone.0290546