The entropic tongue: Disorganization of natural language under LSD |
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| Affiliation: | 1. Department of Psychiatry, Robarts Research Institute, University of Western Ontario, Lawson Health Research Institute, London, ON, Canada;2. Brain Institute, Federal University of Rio Grande do Norte (UFRN), Natal, Brazil;3. Physics Department, Federal University of Pernambuco (UFPE), Recife, Brazil;4. The Forensic and Long Bay Hospitals, Justice and Forensic Mental Health Network, Sydney, NSW, Australia;5. Penticton Regional Hospital, 550 Carmi Avenue, Penticton, British Columbia, Canada;6. Centre for Translational Neuroimaging, Institute of Mental Health, Nottingham, UK;7. Division of Psychiatry & Applied Psychology, University of Nottingham, Nottingham, UK |
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| Abstract: | Serotonergic psychedelics have been suggested to mirror certain aspects of psychosis, and, more generally, elicit a state of consciousness underpinned by increased entropy of on-going neural activity. We investigated the hypothesis that language produced under the effects of lysergic acid diethylamide (LSD) should exhibit increased entropy and reduced semantic coherence. Computational analysis of interviews conducted at two different time points after 75 μg of intravenous LSD verified this prediction. Non-semantic analysis of speech organization revealed increased verbosity and a reduced lexicon, changes that are more similar to those observed during manic psychoses than in schizophrenia, which was confirmed by direct comparison with reference samples. Importantly, features related to language organization allowed machine learning classifiers to identify speech under LSD with accuracy comparable to that obtained by examining semantic content. These results constitute a quantitative and objective characterization of disorganized natural speech as a landmark feature of the psychedelic state. |
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| Keywords: | LSD Psychedelics Natural language Entropy Psychosis |
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