LSD microdosing attenuates the impact of temporal priors in time perception
Family, N., Luke, D. P., Murray-Lawson, C., Sadibolova, R., Terhune, D. B., Williams, L. T. J.
This pre-print re-analysis (n=48) of microdosing LSD (5-20μg) finds that LSD reduces the influence of our expectations (precision-weighted local priors) on what we think time should feel like (under-reproduction bias). When controlling for the expectations, the bias disappears, indicating that LSD microdosing reduces the relative weighting of priors (expectations).
Abstract
Recent theoretical work embedded within the predictive processing framework has proposed that the neurocognitive and therapeutic effects of psychedelics are driven by the modulation of priors (Carhart-Harris $ Friston, 2019). We conducted pre-registered re-analyses of previous research (Yanakieva et al., 2019) to examine whether microdoses of lysergic acid diethylamide (LSD) alleviate the temporal reproduction bias introduced by priors, as predicted by this theoretical framework. In a between-groups design, participants were randomly assigned to one of four groups receiving LSD (5, 10, or 20 μg) or placebo (0 μg) and completed a visual temporal reproduction task spanning subsecond to suprasecond intervals (0.8 to 4 sec). Using mixed-effects modelling, we evaluated the impact of the treatment group, and of the overall history of stimulus intervals (global priors) and the local stimulus history (local priors), weighted by their respective precision weights (inverse of variance), on temporal reproduction. Our principal finding was that the precision-weighted local priors and their precision weights reduced the under-reproduction bias observed under LSD in the original research. Furthermore, controlling for the precision-weighted local prior eliminated the reduced temporal reproduction bias under LSD, indicating that LSD microdosing mitigated the temporal under-reproduction by reducing the relative weighting of priors. These results suggest that LSD microdosing alters human time perception by decreasing the influence of local temporal priors.