"It helps me think"

Plenty of smokers would give up the claim about calm before they gave up this one. You sit down to something difficult, a report or a tax return or a tricky bit of wiring. After forty minutes your attention frays, you go and have a cigarette, and when you come back the problem looks clearer. It's tempting to think of nicotine as fuel for the brain.

Start with the list from chapter 3. Difficulty concentrating is one of the confirmed symptoms of nicotine withdrawal. So is restlessness, and so is impatience. For a regular smoker, those begin to creep in an hour or so after the last cigarette. That's about how long you'd been at the desk.

So part of what happened is easy to explain. Your concentration was being eroded by the falling level of nicotine. The cigarette stopped the erosion. You came back able to think as well as you could before it started, which is to say as well as a non-smoker who'd simply had a five-minute walk. Once again you were given something back, and it felt like a gift.

There's a simple check on this. If cigarettes improved thinking, non-smokers would be at a disadvantage in any job that needs a clear head. Exam halls, operating theatres and air traffic control would be run by people who'd nipped out for one. They're not. The people around you who don't smoke get through difficult work without feeling that their brain stalls every hour.

This is the chapter where I owe you the honesty I promised about the title. Nicotine isn't inert, and the story above isn't the whole story.

In 2010 three researchers at the US National Institute on Drug Abuse, led by Stephen Heishman, pooled 41 laboratory studies of nicotine and mental performance. They deliberately chose studies where withdrawal couldn't explain the result. The participants were either non-smokers, or smokers who'd gone two hours or less without a cigarette. Everything was tested against a placebo, with neither side knowing who'd had what. They found that nicotine produced real improvements in six areas, including fine motor skill, alertness, and short-term and working memory. The authors concluded that these were probably real improvements and not relief from withdrawal.

So nicotine does something. How much is the important part. The effects ranged from small to moderate. In everyday terms, they're in the territory of a cup of coffee. These were also short laboratory tasks, such as pressing a key when a letter appears. They tell you little about whether anyone writes a better report.

Now set that against what it costs to get it by smoking. To collect a small lift in alertness for part of each hour, you accept a dip in concentration for the rest of it, every day, as the level falls. You also accept that on any day you can't smoke freely, in a long meeting or an exam or a flight, you'll think worse than you would have if you'd never started. That trade leaves you behind. I can't point to a study that adds up the two sides for a working day, so treat that sum as my judgement. But I notice that people who want a mild stimulant and have no history with cigarettes choose tea.

Something else did you good in that break, and it's the break itself. Most people find that attention runs down with use. Standing up after forty minutes, walking somewhere, and looking at something further away than a screen will often unstick a problem. Smokers do this many times a day, and non-smokers mostly don't, which is their loss. You've been crediting the cigarette with work that your legs were doing.

If you've already stopped, or when you do, the first couple of weeks may well include some foggy days. That's the withdrawal symptom, and it passes with the others. It helps to know it's coming and not to schedule your hardest piece of thinking for day three. It also helps to keep taking the breaks.