Claudia Hammond is in Sydney, Australia, with a live studio audience at the BBC's World Changing Ideas Summit finding out what is so special about the human mind. Are we the only creatures who can mentally time travel - deciding at will to look back nostalgically at a past event or to look forward, imagining something we've never done before? But the brilliance of the human mind brings its own problems too, a dread of the future or rumination about the past so strong, that a person develops depression. Claudia Hammond's guests are Thomas Suddendorf Professor of child cognition at the University of Queensland and Professor Helen Christensen Chief Scientist at Black Dog Institute, and they discuss whether new technology might hold some solutions for us.