Seeing Is What You Hear: Inducing Visual Hallucinations via Pavlovian Conditioning

Document Type

Student Presentation

Presentation Date



College of Arts and Sciences


Psychological Science

Faculty Sponsor

Brian Stone


Our study aims to create perceptual experience in the absence of sensory stimulation (that is, seeing something that is not actually there). Insofar as perceptual experience is constructed from a combination of past experience and current input to the senses, the perceptual system could be analyzed from a Bayesian perspective as weighing perceptual priors (past experience) and new data (sensory input) to construct a percept guessing at the current state of the world. Our experiment decreases the Bayesian weighting of sensory input by presenting a very dim visual stimulus near the threshold of detection, thus making participants uncertain if they are seeing anything. We then use classical conditioning during training trials (past experience) to induce a specific expectation in the perceptual system: by repeatedly pairing a tone and the visual stimulus during training, the tone comes to predict the presence of the visual stimulus. In occasional test trials, we play the tone without the visual stimulus. In these test trials, the perceptual system is getting no visual input from the eyes but does have an expectation of seeing something based on the past experience during conditioning. We predict that participants will sometimes report a visual experience when nothing is displayed.

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