A few words about Useful-stress. Once you’ve read this, if you’d like to know more, go to the About Stress section.
Useful-stress is a mild worry - like the feeling you have when there's something you need to do before you can really relax.
We think it likely that stress evolved from this useful tool and that it came about like this:
We all know that some problems we need to consider can't be solved immediately. They need more thought, later on.
Imagine now that you're a fish – humour me for a moment – let's say you're a goldfish in a pond. As a temporary goldfish, you are, like all goldfish, fitted with a somewhat unsophisticated memory. Primarily, it helps you to remember dangerous things. Being able to remember dangerous things means that, if you’re attacked again by something similarly dangerous, you’ll instantly know what to do. Useful.
Now, with your goldfish head on, please imagine that you're trying to work out how to get at some food stuck under a ridge. The problem that needs to be solved is simply a matter of what angle is best to try to dislodge a succulent bit of dead fly. It’s not rocket-science but obviously – you being a goldfish and all – it’s taking up a high percentage of your brain-power.
Then, whilst you’re contemplating how to dislodge the fish-food something distracts you. You notice a cormorant overhead sizing you up for lunch. Or perhaps someone sexy (in goldfish terms obviously) flutters their eyelids at you. Goldfish don't normally have eyelids – but this one has. Overwhelmed by the wonders of ecological diversity – and the need to flirt outrageously - you instantly forget the problem of the bit of food stuck under the ledge. With goldfish, thinking is very much a one-thing-at-a-time activity.
The food-problem is not just forgotten. Effectively, it’s lost. You'll never go back to it. In your goldfish guise, once you're distracted, that's it. So, in goldfish-guise, you're rubbish at solving anything more than what you could work out before your mind wanders off somewhere else. And that goes for the vast majority of animals on our planet.
All humans have a common ancestor with a goldfish (as we do with anything else living for that matter, including the fruit flies in the goldfish food - and the bananas the fruit flies fed on). However, as you've evolved over billions of years, your brain-power has become more and more impressive. At some point, you suddenly had enough grey matter to develop a system to remind you to finish things off that you'd had to leave for a while earlier on. It feels like a nagging feeling that you have something that needs doing.
That reminder system is, we think, how what we call 'Useful-stress' – which started out as something that simply tried to remember where danger was - evolved into something that does the positive job of reminding you to finish off solving a problem.