A comprehensive longitudinal study reveals dreams are shaped by personality

A study that analyzed, over four years, thousands of reports of dreams and waking experiences reports that what we dream is shaped by stable individual traits, such as attitudes toward dreaming, the tendency for mind-wandering, and subjective sleep quality.

Dreams are both universal and personal experiences, closely linked to waking life, although often distinct from it. During sleep, the brain generates dynamic narratives shaped by prior experiences, beliefs, expectations, and neural mechanisms that are not yet fully understood.

Dreams have been a subject of study in neuroscience, regarded both as a privileged model for investigating the emergence of consciousness and as a possible pathway to understanding the functions of sleep itself.

Several studies suggest that dream content reflects each individual's memories, concerns, and emotions, and has been associated with learning processes, memory consolidation, and emotional regulation.

What remains less clear is the extent to which stable individual traits and shared experiences over time shape dream content. To address this question, a team of researchers coordinated by Giulio Bernardi (IMT School for Advanced Studies Lucca, Italy), with the support of the Bial Foundation, collected a prospective dataset of dream reports and waking-life experiences to quantitatively and in detail analyse the semantic characteristics of dreams.

In the article "Individual traits and experiences predict the content of dreams", published in the journal Communications Psychology, the researchers explain that they systematically quantified the semantic structure of dreams using 3,366 dream and waking-experience reports collected between 2020 and 2024 from 207 adults, together with demographic, cognitive, psychometric, and sleep measures. To do so, they combined a large language model-assisted evaluation of hypothesis-driven semantic dimensions and a data-driven lexical domain approach.

The results indicate that dream content arises from the interaction between who we are - our relatively stable individual traits and characteristics (such as attitudes toward dreaming, propensity for mind-wandering, and subjective sleep quality) - and what we experience in our daily lives. The data show that elements of waking life can be transformed during sleep, with fragments of reality reshaped and reorganised into new dream narratives.

Rather than constituting a direct reproduction of daily experiences, dreams may offer a hyperassociative reinterpretation of past events and future expectations, weaving together seemingly distant elements into coherent, though often bizarre, scenarios.

A second, independent dataset, collected during the first COVID-19 lockdown in 2020 (80 participants), made it possible to examine the impact of a major external stressor on dream semantics. During the lockdown, dreams showed increased references to limitations and heightened emotional intensity, effects that gradually normalized over the following years.

This study shows that stable individual traits and incidental experiences jointly shape the content and phenomenology of dream experiences. The findings help narrow longstanding gaps between dream research and cognitive neuroscience, offering novel knowledge and tools that will help develop testable hypotheses about the mechanisms linking dream content to memory consolidation, emotional regulation, and consciousness during sleep."

Giulio Bernardi, Associate Professor, IMT School for Advanced Studies Lucca