Decoding the phenomenology of spontaneous thought using large language-model ratings on verbal retrospective free reports
Year: 2026
Type: preprint
Abstract: A bstract Spontaneous thoughts constitute most of everyday inner experience, yet long-standing methodological challenges obscure a thorough exploration of their content and neurophysiological underpinnings. Traditional approaches relying on thought probes impose strict constraints on phenomenological reports, whereas online verbal reports disrupt the natural flow of experience while interfering neural signals with motor artifacts. Here, we designed and tested an alternative approach to assess the neural basis of spontaneous thoughts combining delayed verbal retrospective free reports (RFR) with automated phenomenological ratings generated by large language models (LLMs). Twenty-two participants performed an eyes-closed free-thinking task, providing reports that were evaluated along ten phenomenological dimensions by four state-of-the-art LLMs and a panel of human raters. Machine-learning models (ML) were then trained to decode LLM-derived ratings from EEG spectral, complexity, and connectivity features. Our analyses showed that inter-rater agreement among LLMs exceeded that of human raters whereas ML models achieved above-chance accuracy for the prediction of emotional valence. These findings provide support for the use of LLMs for a scalable phenomenological annotation of spontaneous thoughts and suggest that their affective dimensions can be decoded from concurrent EEG activity.
Institutions: Centre National de la Recherche Scientifique, Consejo Nacional de Investigaciones Científicas y Técnicas, Inserm, Universidad de Buenos Aires, Sorbonne Université, Institut des Sciences Moléculaires, Institut du Cerveau, Tilburg University, Centre de Recerca Matemàtica, Favaloro University, Instituto de Neurología Cognitiva, Centro Uruguayo de Imagenología Molecular, Boston University, Universitat Oberta de Catalunya, Adolfo Ibáñez University, Université Paris Cité
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
Awards: G4671416785, G7188473828
OpenAlex ID: W7155708236