A fancier method of imputation would be multiple imputation using, for example, the R library mice (Multivariate Imputation by Chained Equations) (guide), which will try to impute all missing values in a way which mimicks the internal structure of the data and provide several possible datasets to give us an idea of what the underlying data might have looked like, so we can see how our estimates improve with no missingness & how much of the estimate is now due to the imputation:
The greatly increased variance, but only somewhat increased mean, is consistent with nicotine operating on me with an inverted U-curve for dosage/performance (or the Yerkes-Dodson law): on good days, 1mg nicotine is too much and degrades performance (perhaps I am overstimulated and find it hard to focus on something as boring as n-back) while on bad days, nicotine is just right and improves n-back performance.
These days, young, ambitious professionals prefer prescription stimulants—including methylphenidate (usually sold as Ritalin) and Adderall—that are designed to treat people with attention deficit hyperactivity disorder (ADHD) and are more common and more acceptable than cocaine or nicotine (although there is a black market for these pills). ADHD makes people more likely to lose their focus on tasks and to feel restless and impulsive. Diagnoses of the disorder have been rising dramatically over the past few decades—and not just in kids: In 2012, about 16 million Adderall prescriptions were written for adults between the ages of 20 and 39, according to a report in the New York Times. Both methylphenidate and Adderall can improve sustained attention and concentration, says Barbara Sahakian, professor of clinical neuropsychology at the University of Cambridge and author of the 2013 book Bad Moves: How Decision Making Goes Wrong, and the Ethics of Smart Drugs. But the drugs do have side effects, including insomnia, lack of appetite, mood swings, and—in extreme cases—hallucinations, especially when taken in amounts the exceed standard doses. Take a look at these 10 foods that help you focus.
Jesper Noehr, 30, reels off the ingredients in the chemical cocktail he’s been taking every day before work for the past six months. It’s a mixture of exotic dietary supplements and research chemicals that he says gives him an edge in his job without ill effects: better memory, more clarity and focus and enhanced problem-solving abilities. “I can keep a lot of things on my mind at once,” says Noehr, who is chief technology officer for a San Francisco startup.
The evidence? A 2012 study in Greece found it can boost cognitive function in adults with mild cognitive impairment (MCI), a type of disorder marked by forgetfulness and problems with language, judgement, or planning that are more severe than average “senior moments,” but are not serious enough to be diagnosed as dementia. In some people, MCI will progress into dementia.
The nootropics community is surprisingly large and involved. When I wade into forums and the nootropics subreddit, I find members trading stack recipes and notifying each other of newly synthesized compounds. Some of these “psychonauts” seem like they’ve studied neuroscience; others appear to be novices dipping their toes into the world of cognitive enhancement. But all of them have the same goal: amplifying the brain’s existing capabilities without screwing anything up too badly. It’s the same impulse that grips bodybuilders—the feeling that with small chemical tweaks and some training, we can squeeze more utility out of the body parts we have. As Taylor Hatmaker of the Daily Dot recently wrote, “Together, these faceless armchair scientists seek a common truth—a clean, unharmful way to make their brains better—enforcing their own self-imposed safety parameters and painstakingly precise methods, all while publishing their knowledge for free, in plain text, to relatively crude, shared databases."
A study mentioned in Neuropsychopharmacology as of August 2002, showed that Bacopa Monnieri decreases the rate of forgetting newly acquired information, memory consolidations, and verbal learning rate. It also helps in enhancing the nerve impulse transmission, which leads to increased alertness. Also, it is known to relieve the effects of anxiety and depression. All these benefits happen as Bacopa Monnieri dosage helps in activating choline acetyltransferase and inhibiting acetylcholinesterase which enhances the levels of acetylcholine in the brain, a chemical that is also associated in enhancing memory and attention.
The difference in standard deviations is not, from a theoretical perspective, all that strange a phenomenon: at the very beginning of this page, I covered some basic principles of nootropics and mentioned how many stimulants or supplements follow a inverted U-curve where too much or too little lead to poorer performance (ironically, one of the examples in Kruschke 2012 was a smart drug which did not affect means but increased standard deviations).
Common issues such as poor sleep during pregnancy and sleep deprivation following the birth can often heighten cravings for stimulants and sugary foods, which may seem like a good option for quick sources of energy, however, these foods can often cause further issues with energy and lead to fatigue and low mood. Eating foods that are high in refined sugar and refined grains such as commercial white bread, pastries, cakes and biscuits, give us an unsustainable source of energy. The brain is a very metabolically active organ; despite it only being 7% of the body’s weight, it can take up to 20% of the body’s metabolic needs (2), meaning that it is very energy hungry. This is why it is important to nourish the brain with foods that are nutrient rich, providing the body the building blocks to produce neurotransmitters, as well as a sustainable source of energy. The best options are fresh, unprocessed foods such as wholegrains (brown bread, brown rice, quinoa, rye and oats), pulses, vegetables, good quality sources of protein (meat, poultry and fish) and healthy fats such as those found in olive oil, coconut oil, avocados and oily fish. 

Some work has been done on estimating the value of IQ, both as net benefits to the possessor (including all zero-sum or negative-sum aspects) and as net positive externalities to the rest of society. The estimates are substantial: in the thousands of dollars per IQ point. But since increasing IQ post-childhood is almost impossible barring disease or similar deficits, and even increasing childhood IQs is very challenging, much of these estimates are merely correlations or regressions, and the experimental childhood estimates must be weakened considerably for any adult - since so much time and so many opportunities have been lost. A wild guess: $1000 net present value per IQ point. The range for severely deficient children was 10-15 points, so any normal (somewhat deficient) adult gain must be much smaller and consistent with Fitzgerald 2012’s ceiling on possible effect sizes (small).
Nuts and seeds are terrific sources of vitamin E, which, according to a 2014 study, can help prevent cognitive decline and Alzheimer’s disease as you age. Other vitamin E-rich foods include eggs and cooked veggies. And it’s not just your brain that benefits from nuts; your heart will be happier too. Almonds, walnuts, cashews, Brazil nuts, pistachios, and peanuts have been linked to a decreased risk of cardiovascular disease, according to a Harvard study. Try these other vitamin E-rich foods.
According to Dr. Cohen, there’s no incentive for these companies to conduct trials to determine if their products actually do anything, so few of them do. In fact, he says he isn’t aware of any studies on nootropics that meet the research gold standard: double-blind, placebo-controlled, comparing meaningful numbers of healthy adults (not laboratory mice or rats) in terms of relevant measures of cognitive enhancement.
The evidence? In small studies, healthy people taking modafinil showed improved planning and working memory, and better reaction time, spatial planning, and visual pattern recognition. A 2015 meta-analysis claimed that “when more complex assessments are used, modafinil appears to consistently engender enhancement of attention, executive functions, and learning” without affecting a user’s mood. In a study from earlier this year involving 39 male chess players, subjects taking modafinil were found to perform better in chess games played against a computer.
Brain Pill™ is a mental health enhancing and successfully marketed dietary supplement with a balanced composition of scientifically proven nutrients for accelerating and restoring brain function and thereby enhancing the cognitive performance and creating positive impact on behavioral outcomes.Hence the aim of the study is assessment of the effects of Brain Pill supplementation on memory performance in healthy adults with subjective memory complaints.

Common environmental toxins – pesticides, for example – cause your brain to release glutamate (a neurotransmitter). Your brain needs glutamate to function, but when you create too much of it it becomes toxic and starts killing neurons. Oxaloacetate protects rodents from glutamate-induced brain damage.[17] Of course, we need more research to determine whether or not oxaloacetate has the same effect on humans.
Including comprehensive lists of what to eat and what to avoid, a detailed quiz that will tell you where you are on the brain health spectrum, and 24 mouth-watering brain-boosting recipes that grow out of Dr. Mosconi's own childhood in Italy, Brain Food gives us the ultimate plan for a healthy brain. Brain Food will appeal to anyone looking to improve memory, prevent cognitive decline, eliminate brain fog, lift depression, or just sharpen their edge.

The fact of the matter is, though, that the phrase ‘best brain pill’ doesn’t cover any of the bases you’d want an informative article to cover. The human brain is a large and complex thing, and there are many different kinds of pills, supplements, and medications that you can take to improve or affect different areas and functions. Many more of those pills, supplements and medications you take when it breaks down or glitches, to help control harmful or disorienting symptoms of various mental diseases.

The use of cognition-enhancing drugs by healthy individuals in the absence of a medical indication spans numerous controversial issues, including the ethics and fairness of their use, concerns over adverse effects, and the diversion of prescription drugs for nonmedical uses, among others.[1][2] Nonetheless, the international sales of cognition-enhancing supplements exceeded US$1 billion in 2015 when global demand for these compounds grew.[3]