Psilocybin appears to strengthen this optical illusion, but LSD microdoses do not

A recent study examined the effects of very low doses of LSD on visual perception, specifically how it might alter a well-known optical illusion called contrast surround suppression. This illusion occurs when a striped pattern appears fainter when surrounded by a high-contrast pattern, due to the brain taking context into account.

The researchers led by Lucca Jaeckel sought to find out if low doses of LSD, or psilocybin, could mimic the effects seen with psilocybin in previous studies. The study involved 31 healthy adults, who were randomly given either a placebo or a dose of 10 or 20 micrograms of LSD over the course of three testing sessions. After taking the low dose of LSD, participants completed a visual contrast task on a computer, in which they had to identify the patch that appeared higher in contrast.

The task involved two circular patches of light and dark stripes, one in the center surrounded by high-contrast stripes and the other off to the side without the ring. On average, participants were 28 years old, and about half had prior experience with psychedelics. Four hours after taking the dose, participants filled out questionnaires about their subjective experiences, including how they perceived their vision and overall psychological well-being.

The researchers found that the 20-microgram dose produced a slight alteration in consciousness, with higher scores for visionary changes, oceanic boundlessness, and reduced alertness. Visually, participants reported that 20 micrograms made colors appear more saturated, the world seemed more dynamic, and their vision felt bolder.

However, the 10-microgram dose did not significantly alter perception. The researchers concluded that low doses of LSD could potentially affect visual perception, but further research is needed to understand the extent of these effects.