>>23891682L-Theanine is the only one that I can actually praise as being next most effective after nicotine.
It literally puts your brain within stable alpha waves (specifically around 10 Hz), creating a state of "wakeful relaxation" or "alert calmness" similar to meditation. This state reduces active information processing while boosting creativity and inner-directed attention, effectively keeping the brain calm yet ready for insight. It might sound like you're dumber while in this but it's the opossite, your brain is the most efficient in this state.
As a bonus if you take one before sleep you'll experience childlike feelings, very deep and restorative sleep.