"It helps me think"

Beyond feeling awake, you may feel that coffee makes you sharper. The meeting at four goes better with a cup at three. Ideas come. You're quicker.

There's a second Bristol experiment on this, and it deserves the same careful reading as the first. Rogers and colleagues had two hundred and twelve medium-to-high caffeine drinkers and a hundred and fifty-seven low-or-non drinkers go without caffeine overnight, then tested them through the day, before and after caffeine or placebo. The tests included how sleepy and alert people felt, simple and choice reaction time, a memory task and a tapping task.

The regular drinkers who got placebo got worse as the afternoon went on. Sleepier, less alert, slower reactions, poorer memory for what they'd seen. The shortfall grows through the day. Caffeine improved all of that in the regular drinkers, which is the pick-up. But in the low and non-drinkers, caffeine reduced sleepiness and did little else for mental performance, partly because it also made them jittery and anxious, and the jitters cancelled the benefit. One thing improved in both groups. Caffeine made people physically faster. Tapping speed went up, and so did the speed of simple reactions.

The authors' title is "Faster but not smarter". Their conclusion is that with regular use, tolerance builds to the effect on sleepiness, so that the daily cups don't improve mental alertness or performance. They only restore what going without had taken away.

Put that beside your meeting at four. What the three o'clock cup does is lift your reactions and your alertness from the withdrawal low back to about where a non-drinker sits. It makes you faster. It doesn't make you think better than you'd think at the level. If the ideas come after coffee, it's because the fog has gone, and the fog was the shortfall. A person who wasn't in the shortfall would have had the ideas at three without the cup.

I'll grant that there are situations where faster is what's needed. Driving tired, for one, and there's a section on that in chapter 21. But the daily belief that you think better with coffee doesn't survive the experiment. You think normally with it. You think below normal without it, because you're a regular drinker, and that below-normal state is the thing to get rid of.