Since childhood I've been frustrated by the classic question meant to distinguish optimists from pessimists: "Is the glass half empty or half full?" It seemed impossible to answer in isolation. The best response I could come up with was, "It depends on whether you just poured water into it, or just drank some."
I thought of this recently when discussing the difference between American and British weather forecasts. In America, if a day will contain both sunshine and cloud, the forecast is "partly cloudy." In the UK, however, the forecast for such a day is "sunny intervals." By the old glass-of-water test, this would seem to show that the British are more optimistic than the Americans -- something that goes against both stereotype and my own experience.
But what if the real explanation is that Americans consider sunny weather to be the norm, and mention the clouds because they find them to be the most unusual feature of the day -- whereas the British expect their days to be gloomy, and therefore find spells of sunshine worth commenting upon? Who are the optimists then?