A new study measures the temporal distortions caused by psychedelics

A recent study found that psilocybin, the active compound in magic mushrooms, changes how people perceive time by causing them to underestimate the duration of visual events and feel as though time is passing more slowly. Published in the Journal of Psychopharmacology, the research suggests that these temporal distortions are likely driven by temporary disruptions to attention and memory rather than a change in a hypothetical internal biological clock. These results help clarify the psychological mechanisms behind psychedelic experiences and offer insights into how the human brain tracks the passage of seconds.

Research into psychedelic substances has expanded rapidly in recent years, with a major focus on their potential to treat various mental health conditions. As part of this renewed interest, researchers are examining how these compounds alter basic cognitive functions. One of the most commonly reported effects of psychedelics is a profound distortion of time perception. People using these substances frequently report that time seems to stand still, stretch out, or lose its traditional physical meaning entirely.

Human brains track time across many different scales. We rely on circadian rhythms to manage our daily sleep cycles, and we require rapid neural mechanisms to process sensory information in fractions of a millisecond. The current study focuses on interval timing, which is the ability to perceive and track time in the range of seconds to minutes.

Psychologists often explain interval timing using a mental model that includes an internal pacemaker. This theoretical pacemaker emits steady pulses. When a person needs to estimate a duration, an internal switch allows these pulses to flow into an accumulator. The brain then compares this accumulation of pulses to memories of past durations to make a judgment.

Under normal circumstances, this system allows a person to accurately estimate how long a traffic light takes to change or how long a piece of fruit has been in a microwave. Certain drugs can alter this system. Stimulants that release dopamine tend to make the internal clock tick faster, making people feel like more time has passed than reality dictates. The serotonergic system, which psychedelics target, has a less defined role in this process.

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Previous research on psilocybin and interval timing has yielded mixed results. Past experiments usually asked participants to reproduce a specific time interval by pressing a button for a certain duration or tapping their fingers at a steady pace. Those motor tasks require physical coordination, which can also be altered by psychedelics.

Lead author Petr Scholle, a researcher at the National Institute of Mental Health in the Czech Republic, and his colleagues wanted to see if they could measure time distortion without relying on a participant’s ability to execute physical movements. They also wanted to test whether the distortion applies to visual observation, since past studies mostly used auditory cues. By altering the type of task and the sensory input, the researchers designed the study to test whether psilocybin causes a universal shift in time perception.

To investigate this, the research team recruited twenty-four healthy volunteers for a placebo-controlled, double-blind study. On two separate occasions, participants received either a placebo or an active dose of psilocybin adjusted for their body weight. Neither the participants nor the researchers in the room knew which capsule was being administered on a given day.

The researchers waited four hours after the participants ingested the capsules before conducting the timing task. This waiting period ensured that the most intense visual and cognitive effects of the drug had started to fade. The team wanted to make sure participants could still clearly see a computer screen and understand the instructions of the task.

During the experiment, participants sat in front of a computer and completed a temporal bisection task. First, they went through a training phase where they learned to identify a blue circle shown on the screen for exactly one second as a short duration. They also learned to identify a blue circle shown for exactly three seconds as a long duration.

After the training, the actual test began. The researchers presented the blue circle for various random intervals ranging from one to three seconds. For each presentation, the participants had to use a computer mouse to categorize the circle as either short or long. By gathering responses over many trials, the researchers calculated specific metrics about how the participants judged the time intervals.

One key metric the researchers looked at was the bisection point. This is the exact duration at which a participant is equally likely to categorize the stimulus as short or long. In a person with perfectly accurate time perception, this point would land exactly at two seconds, right in the middle of the one-second and three-second anchors.

Another metric was the just noticeable difference. This value represents the smallest change in duration that a participant can accurately detect. A smaller value indicates high precision, while a larger value suggests that the person’s perception of time is blurry and less consistent.

The researchers observed a shift in the bisection point when participants were under the influence of psilocybin. The participants needed the circle to remain on the screen for a longer duration before they were willing to categorize it as long. Essentially, they underestimated how much time had passed during the trials.

If a circle remained on the screen for two seconds, participants taking psilocybin behaved as if less than two seconds had elapsed. This shift indicates that the internal experience of time had slowed down relative to the actual ticking of a clock. To feel that a normal amount of time had passed, the participants required more actual time to tick by.

Additionally, the participants showed an increase in their just noticeable difference metric while taking psilocybin. Their responses became highly variable, meaning they lost precision in their ability to tell similar time intervals apart. This loss of accuracy was notable for actual durations that lasted longer than two seconds.

At the end of the session, the researchers administered questionnaires to ask participants about their subjective experiences. Participants rated the extent to which they felt time was passing much slower than usual or quicker than usual. The self-reported answers heavily favored the sensation of time slowing down, matching the physical task results.

When the researchers compared the subjective survey answers with the computer task data, they found a clear relationship. The participants who reported the most intense alterations in their perception of time on the questionnaires also tended to have the largest shifts in their bisection point.

The study authors suggest that these time distortions are likely not the result of the drug directly changing the speed of an internal mental pacemaker. Instead, they propose looking at the results through a framework where the brain constantly predicts the world based on prior knowledge and incoming sensory data. When a person is trying to track a duration of several seconds, their brain has to hold onto that incoming sensory information to categorize it.

The researchers propose that the psychedelic state introduces cognitive noise into this system, specifically impairing working memory and attention. For longer intervals in the range of a few seconds, this noise becomes overwhelming. The brain struggles to hold onto the accumulated time pulses, which leads the participant to make early judgments and underestimate the true passage of time.

The study has several limitations that the authors noted. The experiment included a relatively small number of participants, and the timing of the surveys presented a methodological challenge. The questionnaires were given at the very end of the session, meaning participants had to recall their overall experience rather than reporting how they felt during the exact moment of the computer task.

The timing task was also conducted four hours after the substance was ingested, during the waning phase of the experience. Conducting the test during the peak of the drug’s effects might yield different results, though intense visual distortions could make the computer task impossible to complete. The researchers did not explicitly check whether participants were silently counting the seconds in their heads, despite instructing them not to do so.

Future research could explore these temporal effects using different doses of psychedelics or a continuous sliding scale for the surveys to gather more precise subjective feedback. The researchers hope to test specific chemical blockers in the brain to see exactly which serotonin receptors are responsible for the breakdown in time perception. This could help isolate the exact cognitive processes that fail when time seems to stand still.

The study, “The effects of psilocybin on time perception in humans: A comparative analysis of subjective and objective measures,” was authored by Petr Scholle, Štěpán Wenke, Tereza Nekovářová, Yulia Zaytseva, Filip Tylš, Martin Brunovský, Jiří Horáček, Veronika Andrashko, Vlastimil Koudelka, Michaela Viktorinová, Vojtěch Viktorin, Kateřina Hájková, Martin Kuchař, and Tomáš Páleníček.