Effects of short time −30° head-down tilt on time perception

Exposure to microgravity induces abnormal experiences that may affect the perception of time. Head-down tilts (HDTs) are commonly used to investigate the effects of weightlessness. A −30° HDT is considered an appropriate model to simulate the acute phase of microgravity exposure. Temporal performance in a time reproduction task was assessed before and after 30 min of −30° HDT, using 800, 1,000, and 2,000 ms as standard intervals. Absolute error (AE), relative error (ratio), and coefficient of variation (CV) were calculated to quantify performance. Compared to baseline measures obtained prior to HDT, both the mean AE and the ratio were significantly increased after 30 min of −30° HDT at the 800 ms interval. A similar trend was observed at the 1,000 ms interval, but no significant effect was found at the 2,000 ms interval. No significant differences were observed in the CV before and after −30° HDT. Acute exposure to microgravity, simulated by the −30° HDT condition, primarily affects duration perception at sub-second intervals.