At one point while I was at my dad's for Christmas, I made the mistake of trying to get an intelligent response out of my sister before she'd had tea in the morning. She refused to reply to my question until she got her tea – but as soon as a steaming cup was handed to her, she replied immediately and usefully before having taken so much as a sip. I concluded that it wasn't the caffeine she was after so much as the moral support.

I giggled gently at this at the time, but the same thing just happened to me: faced with a strange problem to investigate at work, I decided I couldn't face doing it without a cup of coffee to hand – and yet I have no particular intention of drinking enough of the coffee for the caffeine to begin to take effect before I start on the job. It's just vital, for some reason, to know it's there.