“Legend has it that an observant goatherd named Kaldi discovered coffee in Ethiopia somewhere between about 300 and 800 A.D. He noticed that his goats did not sleep at night after eating coffee berries. He took the berries to a local abbot, who brewed the first batch of coffee, noting its effects on arousal and cognition.”
Some of its effects are strange and contradictory. In many ways caffeine’s effect on your mind is much more about what you expect than what it actually does.
Hopefully you’ll find at least one or two things here to surprise you…
1. Caffeine doesn’t stop most people sleeping
The goatherd Kaldi may have been right about his goats, but not necessarily about humans. Despite all the fuss made about caffeine and sleeping, there’s little evidence that it’s a problem.
The research finds that the vast majority of people have worked out how to use it. It’s not that complicated: don’t have a double espresso at midnight. Duh.
Even then, there are studies where they give people caffeine secretly before they go to bed. Surprise, surprise it doesn’t generally affect their sleep that much!
2. People blame caffeine for anything and everything
It’s not just poor sleep, because people think caffeine is at least a bit bad for them, they blame all kinds of non-specific problems on it: headaches, bad night’s sleep, feeling jittery, and so on.
Researchers sometimes give people placebos and tell them they’ve had caffeine. People subsequently claim to have slept badly, developed headaches and all the rest.
But it can’t be due to caffeine, because they haven’t had any. So it must be down to what we expect caffeine to do to us.
3. Coffee plus nap?
It might seem mad to have a cup of coffee and then go for a nap. But if you’re sleep deprived, this may be the answer.
Studies have tried giving tired people 200mg of caffeine (a cup or two of instant coffee), then telling them to take a nap.
The caffeine plus the nap often has an additive effect on performance. In other words the caffeine improves performance above the nap on its own.
Try it: have a coffee and a nap of around 5-15 minutes and see you feel. Even people who don’t normally nap can find this beneficial.
4. Boosts in sustained attention
Most people feel more alert after a coffee, but are they any sharper when scientifically tested?
The answer is: in some ways yes, but in many ways not.
The strongest positive finding is that caffeine increases sustained attention and vigilance. This is the kind of attention you need to keep doing a relatively routine task that is unchallenging. That’s why it’s often so good at work: it keeps us plodding on through boring stuff that we’ve got to get through.
This finding is particularly strong for people who haven’t had enough sleep, which is most of us nowadays.
When we stray away into other psychological areas like reaction times, learning and memory, things become much less clear. Sometimes caffeine improves them, sometimes it makes them worse and sometimes there’s no difference.
In general, though, there’s little evidence that caffeine makes much difference on tasks that require pure thought.