Un-predictable: Scientists show clever trick to help win at rock, paper, scissors everytime

New research employing advanced brain-imaging techniques reveals a fundamental flaw in human decision-making during competitive games like Rock, Paper, Scissors, confirming that the key to victory lies in absolute unpredictability — a strategy our brains struggle to execute.

The study, which utilised hyperscanning to simultaneously record the brain activity of pairs of players engaged in 15,000 rounds of the simple game, offers novel insights into how past outcomes unduly influence competitive choices, reports Science Alert.

The findings are published in the journal Social Cognitive and Affective Neuroscience.

Conventional game theory dictates that the optimal strategy for winning multiple rounds of a zero-sum game like Rock, Paper, Scissors is to be completely random and avoid being influenced by prior rounds.

However, the study found that this randomness is far easier said than done.

Researchers discovered distinct human biases when players were tasked with choosing their next move:

• Choice Bias: Over half of the participants showed a clear preference bias, favouring "rock" most often, followed by "paper," with "scissors" being the least chosen option.
• Repetition Avoidance: Most players tended to avoid repeating the choice they made in the immediate previous round, making their subsequent actions more predictable than chance would suggest.

This demonstrates that while the best strategy is randomness, most people possess ingrained biases that undermine unpredictability.

By recording real-time brain activity, researchers Denise Moerel, research fellow in Cognitive Neuroscience, Western Sydney University; Manuel Varlet, professor in Cognitive Neuroscience, Western Sydney University, and Tijl Grootswagers, ARC DECRA senior research fellow in Cognitive Neuroscience, Western Sydney University, were able to predict a player's move even before they registered their response, effectively tracking the decision-making process as it unfolded.

Critically, the data revealed that players actively incorporate information about the previous round—both their own choice and their opponent's — into their current decision-making phase.

However, this reliance on the past proved counterproductive, giving rise to a phenomenon the data suggests is a "loser's bias":

"Only the brains of those who lost the previous game had active information about the past outcome. The brains of the winners did not show the same strong influence," this finding suggests that overanalysing and reacting to past failures hinders strategic success, supporting the idea that the best way to win is to reset one's focus after every round.

Beyond the game

While the study used Rock, Paper, Scissors as a simple starting point, the results underscore a critical difference between human and computational decision-making in competitive environments.

"Our research highlights that our brains aren't computers: we can't help but try to predict what'll happen next, and we rely on past outcomes to influence our future decisions, even when that might be counterproductive," the scientists noted.

In competitive scenarios where unpredictability is advantageous, this innate tendency to rely on history can be a significant liability as states the report.

Conversely, this bias is often beneficial in most social contexts, where predictability facilitates cooperation and understanding. The key takeaway for future success, the scientists conclude, is clear: people who stop overanalysing the past may have a better chance at winning in the future.