Psychedelic Cognition-The Unreached Frontier of Psychedelic Science

The paper is a narrative review based on a manual search of the literature. Searches were performed from April 2020 to August 2021 on PubMed and Google Scholar using combinations of terms relating to cognition (for example, cognition, memory, attention, reasoning, creativity, social cognition) and psychedelic substances (psychedelics, LSD, psilocybin, DMT, mescaline). For each search term the author substituted the general term with specific compounds to capture compound-specific studies. Inclusion was limited to human studies that assessed the impact of psychedelic drugs on cognition using formal cognitive tasks; animal studies were excluded to preserve ecological validity for human cognition. The extracted text does not report use of a formal systematic-review protocol (for example, PRISMA), a formal risk-of-bias or quality assessment, or quantitative meta-analytic pooling; instead the review integrates and contrasts findings across domains and highlights methodological heterogeneity. The prose indicates that a Supplementary Table summarises all included studies, but the extracted text does not provide details of exact numbers of studies included, criteria for exclusion beyond task-based human studies, nor a formal appraisal of study quality.

Across the cognitive domains reviewed, the literature is characterised by small sample sizes, heterogeneous paradigms, varied doses (from microdoses to high doses), differing timepoints of assessment during the psychedelic experience, and a predominance of laboratory-based studies with relatively few naturalistic investigations. Memory: Findings are mixed and appear dose dependent. Several studies reported working memory impairments at medium-to-high doses of psilocybin and ayahuasca (for example, increased errors on Sternberg and other tasks in samples of 12–24 participants), whereas other studies found no effect using spatial span or similar tasks in smaller samples (for example, eight volunteers). Microdose studies of LSD found no consistent effects on working memory in larger samples (up to 48 participants). Different memory tasks (Spatial Span, Sternberg, Letter N-back, CANTAB PAL) and dose differences likely contribute to discrepant outcomes. Open questions noted include whether psychedelics alter memory reconsolidation, the permanency of any impairments, and whether specific doses could facilitate autobiographical recall or be protective against dementia — none of which are settled by current data. Attention: Results again vary with dose and substance. Several small studies implicate impairment of attentional filtering under DMT and medium-to-high psilocybin doses (for example, reduced inhibition of return, impaired sustained attention, and reduced attentional tracking in studies with sample sizes typically in the teens), while low doses of LSD were associated with improved performance on a psychomotor vigilance task in one study of 24 volunteers. Microdosing studies using CANTAB Rapid Visual Information Processing reported no effect on attention in 48 participants. Taken together, the literature suggests that low doses may sometimes enhance attention whereas higher doses more consistently impair the ability to suppress distracting stimuli, but more work is required to define dose–response relationships and substance-specific effects. Reasoning and executive function: The available studies are sparse and inconsistent. Some experiments report impaired executive control under medium doses (increased errors on switching Stroop tasks, impaired go/no-go performance, longer reaction times), with sample sizes typically in the mid-teens to twenties. Naturalistic ayahuasca data suggested that inexperienced users showed impaired planning on a Tower of London task whereas experienced users did not, pointing to a possible moderating role of prior psychedelic experience. Microdose studies produced mixed results: some reported no effect on abstract reasoning (Raven’s Matrices) or digit substitution performance, while another reported impairment on a digit substitution task at a low LSD dose (20 µg). Overall, the review concludes that higher doses tend to slow or impair planning and inhibitory control, though heterogeneity of tasks, doses and participant experience limits firm conclusions. Emotional and social cognition: Several studies, primarily of psilocybin and LSD, indicate alterations in emotional face processing and empathy. Psilocybin has been reported to reduce recognition of negative facial emotions and enhance recognition of positive expressions, biasing perception toward positive cues, while increasing emotional empathy in multiple samples (for example, 17–32 participants on tasks such as the Multifaceted Empathy Test). Some studies found no change on moral dilemma tasks, suggesting empathy changes do not necessarily alter moral reasoning. Ayahuasca studies gave mixed timing effects, with some empathy changes emerging immediately and others a week later. Small studies of social decision-making found reduced rejection of unfair offers under psilocybin, and reduced perceived social exclusion in Cyberball paradigms without changes in objective ball-pass counts. Microdosing of LSD did not consistently modify affective ratings or responses to social rejection. The pattern suggests psychedelics can enhance prosocial feelings and reduce perceived exclusion, but may also increase susceptibility to social influence or acceptance of unfairness. Creativity, suggestibility and language: Evidence on creativity is heterogeneous and task-dependent. A naturalistic study reported that psilocybin microdoses increased divergent thinking (Alternative Uses Task) and convergent thinking (Picture Concept Task) in one sample, while another controlled study found that a normal dose of psilocybin impaired divergent and convergent thinking during the acute phase but that divergent thinking increased after the dose wore off. Microdosing LSD studies often reported null effects on convergent thinking. Suggestibility appeared increased under LSD in two small studies. Language under the influence shows recognisable alterations: analyses of speech during LSD sessions revealed increased verbosity, reduced lexical diversity and disorganisation akin to patterns observed in psychosis; some early longitudinal observations suggested persistent changes in figurative speech with long-term use in a few individuals. Across creativity and language domains, context, set and setting, and spontaneous insight are emphasised as influential and difficult to capture in laboratory paradigms. Adverse effects and side observations: The review notes common methodological constraints but also records adverse or undesired effects reported in some studies, notably headaches following microdosing in some samples and dose-related headaches with psilocybin, alongside reports that psychedelics can alleviate cluster headaches in other contexts. The extracted text emphasises that most findings rest on small, heterogeneous samples and that a comprehensive synthesis of effect sizes was not provided in the reviewed material.

Ȃl interprets the assembled literature as encouraging but insufficiently mature to support strong claims about how psychedelics affect cognition acutely. The discussion highlights recurring themes: small sample sizes, heterogeneous cognitive paradigms, inconsistent dosing strategies, limited timepoint sampling during the psychedelic experience, lack of replication, and an over-reliance on healthy volunteers in tightly controlled settings. These factors together limit generalisability and hamper efforts to define dose–response relationships, substance-specific profiles, and the roles of prior psychedelic experience or clinical status. The author stresses the particular importance of studying cognition in naturalistic settings and across multiple timepoints during the trip because cognition may be impaired at peak intoxication yet enhanced during the afterglow. Set and setting are repeatedly cited as critical moderators, and translating laboratory findings to recreational contexts is presented as scientifically unsound and potentially hazardous. The discussion also raises policy and clinical concerns: rapid proliferation of clinics and relaxed laws may outpace the evidence base, and insufficient understanding of acute cognitive effects could have safety implications for patients and recreational users alike. Recommendations for future research include standardising and validating cognitive testing batteries across studies, expanding investigations to all classical psychedelics (including less-studied compounds such as mescaline), using within-subject designs with larger and more heterogeneous samples (including clinical populations), systematically varying dose and sampling timepoints, and incorporating naturalistic and longitudinal follow-up to detect sustained benefits or harms. The author also calls for attention to side effects such as headaches and for unified, reproducible approaches that permit replication and inform harm-reduction measures and policy.