"It gives me a lift"

It does give you one. I want to be straight about this, because a book that told you the pleasure was imaginary would lose you at the first biscuit.

Michael Macht and Jochen Mueller, psychologists at the University of Würzburg, tested it directly. They showed volunteers film clips chosen to put them in a sad mood, a happy mood or a neutral one. Then they gave them either a piece of chocolate or a drink of water. When people were in a low mood, the chocolate improved it, and the water didn't. In a second experiment they compared chocolate that tasted good with chocolate that didn't, and only the good chocolate helped. So the lift exists, and it comes from the pleasure of the taste.

The second experiment also measured how long the improvement lasted, and it was gone after three minutes.

That figure comes from one laboratory and one kind of chocolate, and I wouldn't insist on the exact number. But it fits what you can observe for yourself, and I'd encourage you to observe it. The pleasure of a biscuit is mostly in the first bite or two, while the taste is new. It fades as you chew. A minute after you've swallowed the last of it, you're back where you were, with a slight wish for another one.

Once you know the size of the lift, a few things about the habit make more sense.

It explains why one becomes two. The first biscuit delivered its lift and the lift has gone, so the hand goes back to the tin to fetch another. The second delivers a bit less, because the taste is no longer new. By the fourth, on the sofa, you're eating to chase something that the biscuits stopped providing two biscuits ago. You noticed that yourself on Thursday night, when you couldn't describe the taste of the last two.

It explains why you eat them fast and while doing something else. If the point is a quick hit of pleasure, there's no reason to sit down and attend to it. But a pleasure you don't attend to is hardly a pleasure at all, which makes the return even smaller.

And it shows what the three jobs are up against. A reward, a pick-me-up and a comfort are all meant to change how the next hour or the rest of the evening feels. The tool you're using works for about as long as it takes to boil the kettle. Whatever the tin is doing for you at four o'clock or at half past nine, it isn't the lift, which was over long before.

None of this is an argument against enjoying chocolate. Three minutes of real pleasure is worth having, and chapter 11 is about how to get more out of it. But a few minutes of pleasure can't do a job that needs an hour or an evening.