Monkey Janken |work| -

The image of a macaque performing the classic fist (rock), flat palm (paper), or two fingers (scissors) is undeniably endearing. However, for primatologists and cognitive scientists, it is profoundly significant. A monkey cannot be taught Janken through verbal instruction alone. Instead, researchers have successfully trained primates using a reward-based system of "conditional discrimination." The monkey learns that a specific visual cue (a flat hand) defeats another (two fingers). This seemingly simple act requires the primate to suppress a natural instinct—grabbing for the food—and instead execute an arbitrary, symbolic rule.

In Japan, the simple hand game known as Janken (what the West calls Rock-Paper-Scissors) is so deeply ingrained in the culture that it transcends mere game status; it is a tool for resolving disputes, choosing a captain, or deciding who pays for dinner. But when we observe Sarujanken (Monkey Janken), we are not just watching a party trick. We are looking into a mirror that reflects the evolutionary link between conflict resolution, abstract thought, and social bonding. monkey janken

This ability is the cornerstone of abstract thought. When a monkey holds out paper to "cover" your rock, it is not pretending its hand is a sheet of paper; it is engaging in a symbolic contract. It understands that the gesture represents a tool or object. As the famous Japanese primatologist Tetsuro Matsuzawa noted, the chimpanzee's ability to learn the hierarchical logic of Rock-Paper-Scissors demonstrates a cognitive flexibility previously thought unique to humans. The image of a macaque performing the classic