In 2007, researchers Sana Inoue and Tetsuro Matsuzawa at the Primate Research Institute of Kyoto University designed a study with one precise goal: to compare visual working memory for numerals between chimpanzees and humans under identical, controlled conditions. This was not a test of general intelligence but of a specific, fleeting cognitive skill.

The experiment emerged from decades of primate cognition research at Kyoto University, where scientists had already demonstrated chimpanzees’ ability to learn Arabic numerals and sequence them. However, this study aimed to push further — to test the speed and accuracy of visual memory when time became the critical constraint.

What the “Limited-Hold Memory Task” Actually Measured

The experiment isolated the transition from iconic memory (a sub-second visual snapshot) to visual working memory (active holding of that information). For more on different memory types, see our guide on working memory vs short-term memory. This experiment did not test:

• Long-term memory
• Language skill or comprehension
• Mathematical reasoning
• Overall IQ or general intelligence
• Problem-solving ability

Instead, it focused purely on one question: “How well can different species retain a brief visual stimulus?” This specificity is crucial for understanding what the results actually mean.

Laboratory Setup: The Controlled Touchscreen Method

To ensure a fair comparison, the researchers used a touchscreen interface, completely removing any human language advantage. The experimental setup featured several rigorously controlled variables:

Step-by-Step: How the Task Worked

The experimental procedure followed a precise sequence:

1. Numbers 1-9 appeared randomly on a touchscreen
2. The subject (chimp or human) touched the number “1”
3. Crucial Step: Upon touching “1”, all remaining numbers instantly turned into blank white squares
4. The subject had to touch the squares in ascending numerical order (2, 3, 4…) based purely on memory

Why the “Masking After First Touch” Was Genius

This design element was critical — it eliminated any possibility of “cheating” by continuous looking. Once the first number was touched, the visual information disappeared entirely, forcing the brain to rely completely on the visual snapshot encoded during the initial, brief display. This made it a pure test of instantaneous visual-spatial recall, a phenomenon related to attention blink in humans.

Experimental Results

The data revealed a striking divergence between human and young chimpanzee performance as display times decreased:

Note: Ayumu, the young chimpanzee, maintained approximately 80% accuracy even at 210ms display time, while human accuracy dropped to near 40% at the same interval. For context on exceptional memory abilities, read about eidetic memory.

Interpreting the Results

Ayumu’s exceptional performance highlights the concept of cognitive specialization across species. The leading hypothesis suggests an evolutionary trade-off: young chimps may have evolved enhanced capacity for rapid visual encoding, possibly because human cognition allocates more resources to functions like:

• Language processing and syntax (related to verbal memory)
• Complex, long-term planning
• Abstract reasoning and symbolic thought
• Social cognition and theory of mind

As lead researcher Dr. Matsuzawa noted: “This doesn’t mean chimpanzees are smarter than humans overall. It means they’ve developed exceptional skill in one specific cognitive domain that was likely crucial for their survival in forest environments.” For a deeper analysis of why chimps excel at this specific test format, see our article on why chimps are better at the chimp test.

Common Misconceptions (Myth vs. Fact)

Lab Task vs. Online “Chimp Test” 

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If you’ve taken an online “chimp test,” you might notice it feels different from the lab study. Here’s why:

The Scientific Legacy & Limitations

This experiment’s major contribution to cognitive science was demonstrating the modular nature of intelligence. Different species develop cognitive strengths adapted to their specific environmental pressures and evolutionary histories.

The study is also notable for its methodological rigor and clear acknowledgment of limitations:

• Tests only one specific skill under controlled conditions
• Results are not diagnostic of individual ability
• Performance varies significantly with age (young chimps outperform adults)
• Cannot be generalized to all memory types or cognitive functions