A researcher has discovered that monkeys quickly notice snakes due to the visual cue provided by snake scales. His work emphasizes an evolutionary change in primates that helps them recognize snakes by certain visual traits. By understanding how this works, we can gain knowledge about the evolution of visual processing related to detecting threats.
Dr. Nobuyuki Kawai from Nagoya University in Japan has discovered that monkeys can swiftly detect snakes because they pick up on the visual cue of snake scales. This research reveals an evolutionary shift in primates, allowing them to recognize snakes through distinct visual traits. Grasping these processes offers valuable insight into the evolution of visual systems that help detect threats. The findings appeared in Scientific Reports.
Quickly identifying dangers is crucial for personal protection. Throughout history, snakes have represented a lethal threat to primates, including humans. Notably, monkeys and even human infants, even those who have never seen a snake, exhibit reactions to images of these reptiles, reflecting an inherent fear of them.
Kawai’s initial experiment showed that monkeys reacted quickly to snake images but not to salamander images, indicating a specific fear of snakes. This led him to wonder whether modifying salamander pictures to include snake scales would change their response. Would monkeys respond to the scales, or would they still recognize the harmless salamander?
To explore this, Kawai showed monkeys—who had never seen real snakes—nine images on a board and trained them to identify the unique one to earn a reward. When the monkeys were presented with one snake among several salamanders, they quickly located the snake compared to finding a salamander among snakes. This suggests the monkeys had a heightened reaction to the potentially harmful reptile.
Interestingly, when Kawai presented the altered salamander images that featured snake scales, the monkeys responded just as swiftly, if not quicker, to these edited images than they did to the actual snake.
“We had already shown that humans and primates can swiftly recognize snakes; however, we were unaware of the specific visual feature at play,” Kawai stated. “The monkeys didn’t show a quicker response to salamanders—a species similar in shape and form to snakes—until the images were modified to display snake scales.” This indicates that the scales were what made the monkeys feel most threatened.
“Perhaps this is due to our primate ancestors developing a visual system to recognize scales, which are typical of snakes,” he added. “Understanding this aspect of primate evolution can enhance our comprehension of vision and brain development not just in animals, but in ourselves as well.”
