The sight of the little girl waving from her hospital bed was enough to bring a smile to anyone's face. Over two weeks had passed since she had disappeared from a campsite in a remote partThe Coral Coast, known for its dramatic ocean scenery. of Western Australia. There had been a massive air, land and sea search, but hopes of finding her had started to fade. It was, said police deputy commissioner Col Blanch, like looking for a needle in a haystack.

Then, yesterday, came the news that Cleo Smith was safe. "One of the officers picked her up into his arms and asked her, 'What's your name?'" Blanch reported. "She said, 'My name is Cleo'." It had been incredible, he added, to see seasoned detectives openly crying with relief.

"Our family is whole again," wrote her mother on Instagram. Australia's prime minister, Scott Morrison, called it "wonderful, relieving news".

Looking at the other headlines, though, Cleo's story seemed like an oasis of happiness in a desert of misery. The end of Covid-19 was still not in sight, with cases up in many countries and vaccination programmes slowing down. Joe Biden's Democrats had been defeated in a gubernatorialGovernor's. The worry is that the result increases Donald Trump's chances of being re-elected and increasing the US's carbon emissions. election, putting the future of his clean energy plans in doubt.

Then there was Ethiopia's government declaring a state of emergency after advances by rebel troops. In Yemen, three million people in the city of Marib were threatened with a siege by HouthiThe Houthis represent a Shia Muslim minority, but have won support from other Yemenis dissatisfied with the government. fighters. In Sweden, two people were dead after an accident at an Abba tribute concert.

And yet, looked at in another way, the world is full of hope and happiness. An inflatable playground has been invented which removes carbon emissions from the air. A former refugee, Abdulrazak GurnahThe author and his family had to flee from Tanzania when he was 18., has won the Nobel Prize for literature after working in obscurity for 50 years.  

France's first public official with Down's syndrome, Eleonore Laloux, has been awarded the country's second highest honourThe National Order of Merit. The highest award is the Legion of Honour.. A Canadian called Jerry Knott, who bought a lottery ticket and then forgot about it, discovered that he had won $20m - and decided to spend it on his local community.

The actor Michael J. FoxThe actor is best known for playing the lead role in Back To The Future. has passed the $1.5bn mark in his fundraising for research into Parkinson's diseaseA condition which affects the part of the brain controlling movement.. Though the condition almost ended his career, he says he is happier at 60 than when he was a young star: "I feel great. I love life. It's great to be a part of something so important."

So why does bad news dominate our lives? According to John T Cacioppo, a psychologist at Ohio State University, it is because negative things make a bigger impact on our brains than positive things. From the beginning of human history, our survival has depended on avoiding danger - so our brains have developed to alert us to anything bad coming in our direction.

Another theory is that people generally look on the bright side of life. "This pleasant view of the world makes bad news all the more surprising and salientConspicuous. In military terms, a salient is part of a fortification which sticks out.," writes another psychologist, Tom Stafford. "It is only against a light background that the dark spots are highlighted."

Some say, yes. Too much bad news can cause not just anxiety but depression and anger - and because of social media humans are more exposed to it than ever before. We need to redress the balance and put more emphasis on positive events to save people from being overwhelmed.

Others argue that the instincts which made the brain develop as it has are still hugely important. The world is an alarming place, and we need to be aware of all its dangers in order to deal with them. If the headlines did not make us worry about climate change, nothing would be done to combat it.