From the paper:

Currently, psychedelics are experiencing a third-wave resurgence—the first wave was the traditional use by native peoples from civilizations around the world for thousands of years, the second wave was the heavy scientific and recreational usage in the 1960s that resulted in their ban, and the third wave is the current use of LSD and psilocybin to assist in medical and psychological situations, including recent Food and Drug Administration–approved studies by researchers at Johns Hopkins, Yale, NYU, and various other facilities who have confirmed the positive cognitive effects of psychedelics.7 8 Scientists, Silicon Valley executives, biologists, biohackers, and others who face complex problems or operate at high performance levels are also using microdosing to gain a mental advantage with psychedelics.

Microdosing

A microdose is a sub-perceptual amount (i.e., it does not cause percep- tual sensory changes such as visual hal- lucinations and is not strong enough to debilitate the subject) consisting of about a tenth of a medicinal dose of any given psychedelic, usually between 10 and 20 micrograms (μg) of LSD or 100 milligrams (mg) of psilocybin. In research, microdoses were reported to significantly heighten alertness, creativ- ity, and problem-solving—inducing a “flow state” that aids in lateral thinking.

Ben Greenfield covers cognitive enhancers in his book (see: Biohacking Books) and I’ve often heard people talk about devs microdosing when I used to be active on Twitter.

Personally, I would stick to natural herbals - plenty of which can enhance cognitive function (and also covered in Ben’s book).