What is Parrondo’s paradox? – The Hindu

A: Parrondo’s paradox is a strange idea from game theory (and before that from physics). It shows that when two losing strategies are alternated in a particular sequence, the outcome can be a winning strategy. A common way to picture this is with coin-tossing games: even if each game individually drains your money by stacking the odds against you, switching between them at specific intervals can allow your fortune to grow instead of shrink. The paradox has become a useful tool across science to explain how mixing two bad options can create a better result.

In cancer therapy, for example, doctors often use two main chemotherapy schedules. The maximum tolerated dose (MTD) blasts tumours with high doses of drugs at spaced intervals. While powerful at first, MTD tends to leave behind resistant cancer cells that eventually take over. The low-dose metronomic (LDM) schedule delivers smaller, continuous doses. But if the dose is too weak, sensitive cells escape control, and if it is too strong, resistant cells dominate.

A study published in Physical Review E in August 2025 tested what happens when MTD and LDM are alternated rather than applied alone. Using mathematical models and computer simulations, researchers found that cycling between MTD and LDM could delay the rise of resistant cells and preserve healthy cells longer. In effect, the strategy — which still needs to be tested in a real-world setting — achieves what neither one could do so alone: more effective long-term control. This is a weak form of Parrondo’s paradox.