Background: Microdoses of psychedelics (i.e. a sub-hallucinogenic dose taken every third day) can reduce symptoms of depression, anxiety and stress according to anecdotal reports and observational studies. Research with medium to high doses of psilocybin points towards potential underlying mechanisms, including the modulation of emotion and interoceptive processing. Aims: In this preregistered study, we investigated whether psilocybin microdoses alter self-reported interoceptive awareness and whether repeated microdosing over 3 weeks modulates emotion processing and reduces symptoms of anxiety and depression. Methods: We used a double-blind, placebo-controlled, within-subject crossover design. Participants completed the Multidimensional Assessment of Interoceptive Awareness Questionnaire 1½ h after self-administering their second dose (or placebo), and the emotional go/no-go task and the shortened Depression Anxiety Stress Scale 1½ h after self-administering their seventh dose. Results: Our confirmatory analyses revealed that psilocybin microdosing did not affect emotion processing or symptoms of anxiety and depression compared with placebo. Our exploratory analyses revealed that psilocybin microdosing did not affect self-reported interoceptive awareness, that symptoms of depression and stress were significantly reduced in the first block compared with baseline, that participants broke blind in the second block and that there was no effect of expectations. Further research in a substance-naïve population with clinical range anxiety and depressive symptoms is needed to substantiate the potential beneficial effects of microdosing.

There is an increased societal trend to engage in microdosing, in which small sub-hallucinogenic amounts of psychedelics are consumed on a regular basis. Following subjective reports that microdosing enhances the experience of nature and art, in the present study we set out to study the effects of psilocybin microdosing on feelings of awe and art perception. In this preregistered combined field- and lab-based study, participants took part in a microdosing workshop after which they volunteered to self-administer a psilocybin microdose or a placebo for three consecutive weeks, while the condition was kept blind to the participants and researchers. Following a 2-week break, the condition assignment was reversed. During each block, participants visited the lab twice to measure the effects of psilocybin microdosing vs. placebo. We used standardized measures of awe, in which participants reported their experiences in response to short videos or when viewing abstract artworks from different painters. Our confirmatory analyses showed that participants felt more awe in response to videos representing funny animals and moving objects in the microdosing compared to the placebo condition. However, about two-third of our participants were breaking blind to their experimental condition. Our exploratory findings suggest that expectancy-effects may be a driving factor underlying the subjective benefits of microdosing.

Space and time can each act as scaffolds for the individuation and selection of visual objects in working memory. Here we ask whether there is a trade-off between the use of space and time for visual working memory: whether observers will rely less on space, when memoranda can additionally be individuated through time. We tracked the use of space through directional biases in microsaccades after attention was directed to memory contents that had been encoded simultaneously or sequentially to the left and right of fixation. We found that spatial gaze biases were preserved when participants could (Experiment 1) and even when they had to (Experiment 2) additionally rely on time for object individuation. Thus, space remains a profound organizing medium for working memory even when other organizing sources are available and utilised, with no evidence for a trade-off between the use of space and time.

Introduction: Microdosing refers to the repetitive administration of tiny doses of psychedelics (LSD, Psilocybin) over an extended period of time. This practice has been linked to alleged cognitive benefits, such as improved mood and creativity, potentiated by targeting serotonergic 5-HT2A receptors and facilitating cognitive flexibility. Nonetheless, in the absence of robust, quantitative and double-blind research on the effect of microdosing, such claims remain anecdotal.Methods: Here, our main aim was to quantitatively explore the effect of microdosing psychedelic truffles on two creativity tasks assumed to rely on separable processes: the Picture Concept Task assessing convergent thinking and the Alternative Uses Task assessing divergent thinking. We present results from 3 double-blind placebo-controlled longitudinal trials (of which one was pre-registered) conducted in a semi-naturalistic setting. Furthermore, we controlled for expectation and learning biases, and the data were mega-analyzed across trials with a pooled sample of 175 participants in order to maximize statistical power.Results: In the final analyses we found that active microdosing increased the ratio of original responses (originality/fluency), indicating higher quality of divergent answers in the active microdosing condition. The unadjusted originality score was significantly more pronounced in the active microdosing condition, but only when relative dosage (dose/weight of participants) was considered. These effects were present after controlling for expectation and demographic biases. No effects of active microdosing were found for convergent thinking or any other divergent-thinking score. The results suggest that the effects of truffle mirodosing are limited to divergent quality and are more subtle than initially anticipated. Our findings furthermore highlighted the importance of controlling for expectation biases, placebo effects, and prior psychedelic experience in microdosing practice and research.

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