When my dog Shadow was a baby she learned a trick. I usually keep a glass of water on my bedside table at night. She would crawl onto my chest and stare at it, growling, until I lifted it to her nose, tilted the glass and gave her a sip.

After enough times of this, even if there was no glass of water, her clamoring up to my chest, staring at the bedside table and growling meant: I’m thirsty, please give me some water.