WITH its potential to boost productivity across multiple industries, artificial intelligence (AI) is the stock market investment theme of the year. But if you ask traders how AI is changing investing itself, their answers might underwhelm: Twitter-reading robots, data analysis tools or algorithms for routing buy and sell orders. For financial markets, the holy grail remains a form of AI that can tell where prices are headed more accurately than a human can – a challenge that is far tougher than teaching a computer to summarise a research report.