Believing in simulated virtual scents produces reported olfactory sensations

Predictive processing (PP) refers to the brain's ability to incorporate present and prior sensory information about states of the body and the environment, enhancing various cognitive functions including perception, motor control, decision-making, and theory of mind. The PP framework conceptualizes the brain as a probabilistic prediction engine that continuously generates top-down predictions about the causal structure of the world. This approach has provided significant explanatory power, offering what many consider a first glimpse of a unified theory of the mind. However, olfactory perception and sensation in the context of PP remains an understudied subject. We present substantial evidence for olfactory sensations as being constructed via predictive processes. We discovered, in a pre-registered and controlled behavioral experiment, that when participant's short-term priors of olfactory sensations are manipulated by instilling a belief that olfactory stimuli have been modelled as part of a virtual reality experience, participants report diverse olfactory sensations. The results demonstrate how mind's capability of constructing reality extends from previously studied sensory modalities such as vision or taste to olfaction. The study initiates the framework for refined experimental designs on predictive olfaction utilizing virtual stimuli and potential applications for therapeutic treatments of individuals with deficiencies in olfactory functioning or neurogenerative diseases.