Perceptual Changes and Time Perception

What this page covers

Perceptual changes are among the most consistent effects reported with psychedelic and dissociative substances. This page describes what controlled studies, a regulator-approved label and a federal research institute report. It is information only. It is not a guide to using any substance, and it does not predict what any one person would experience. For the wider picture of how different people respond, see why experiences vary.

Vision, hearing and imagery

The National Institute on Drug Abuse (NIDA) says people who take psilocybin may see colors, shapes or scenes, hear things that are not real, or lose their sense of time and space. [2]

This increase was blocked when the 5-HT2A receptor, a docking site for the brain chemical serotonin, was blocked with a second drug (ketanserin). It was also linked to a loss of self-boundaries. [3] Label: insufficient evidence to generalize (one controlled study of 25 healthy volunteers; it says little about people with health conditions).

The sense of time

Time distortion is often mentioned. Researchers have tried to measure it with tasks rather than only with questionnaires.

• Longer intervals were harder. In a double-blind placebo-controlled study with 12 healthy volunteers, psilocybin impaired the ability to reproduce intervals longer than about 2.5 seconds, to tap along with beats more than 2 seconds apart, and slowed the preferred tapping speed. [4]
• Other changes came along with it. Working memory was also worse, and volunteers reported more depersonalization and derealization (feeling detached from yourself or your surroundings), including disturbances in their sense of time. [4]
• A second small set of experiments. Two double-blind placebo-controlled studies (12 and 9 people) found that psilocybin changed a model parameter describing how quickly the internal representation of a time interval is lost, measured 90 minutes after intake. The authors only tentatively linked this to altered subjective time. [5]

These are very small samples. A task measuring how people reproduce a few seconds is not the same as the lived feeling of time stretching or stopping, and the authors of both studies were cautious about connecting them.

Do perceptual effects mean benefit?

No source we read shows that vivid visuals are what make a treatment work. In one survey of people planning their own psychedelic experience, higher ratings of "mystical-type" experience were linked with a rise in well-being, while ratings of visual effects were not. [7] That was an online survey, not a trial, so it suggests an association only. See mystical-type experience measures and proposed mechanisms vs proven clinical outcomes.