Some studies have shown that Nicotine increases concentration, attention, and memory..
Harnessing Nicotine's Power to Aid Concentration, Attention
On the Patch
and this one is amazing
Smoking is 'good for your memory and concentration' | Mail Online
It says:"Experts are developing drugs that copy the active ingredients in tobacco that stimulate the brain without causing heart disease, cancer, stroke or addiction. The move follows the discovery that nicotine can boost the intelligence and recall ability of animals in laboratory experiments......"
....."Prof Stolerman's team have studied how nicotine alters the brain's circuitry to boost memory and concentration - and identified some of key brain receptors and chemical messengers - such as dopamine and glutamate - that are involved.
They also found differences in the chain of events that leads to boosted brain power - and the chain of events that leads to addiction.
"We believe that by building on these differences it may be possible for medicinal chemists to devise compounds that produce some of the beneficial effects of nicotine," he said."
Another says: "Depending on the amount taken in, nicotine can act as either a stimulant or a sedative. Cigarette smoking has definite immediate positive effects. For example, it can:
* .Boost mood and relieve minor depression
* .Suppress little fits of anger
* .Enhance concentration and short-term memory
* .Produce a modest sense of well-being
Most smokers have a special fondness for the first cigarette of the day because of the way brain cells respond to the day's first nicotine rush. Nicotine, particularly taken in the first few cigarettes of the day, increases the activity of dopamine, a chemical in the brain that elicits pleasurable sensations, a feeling similar to achieving a reward.
Over the course of a day, however, the nerve cells become desensitized to nicotine. Smoking becomes less pleasurable, and smokers may be likely to increase their intake to get their "reward." A smoker develops tolerance to these effects very quickly and requires increasingly higher levels of nicotine."
(This is just one page I did searching Google "Nicotine helps concentration")