Psilocybin changed how rats evaluated rewards during decision-making tasks. Rats given a single 1 mg/kg psilocybin dose chose the large delayed reward less often 48 hours later, showing a measurable drop in reward-seeking behavior compared with untreated animals. The effect appeared across multiple delay intervals (1, 10, and 20 seconds), indicating psilocybin altered how the animals weighed reward value rather than simply their tolerance for waiting.