A rush of interest in artificial intelligence (AI) has helped to fuel a $4tn (£3.2tn) rally in technology stocks this year, with the US Nasdaq exchange reaching its highest level since last August in a week that saw the chipmaker Nvidia poised to become the next trillion-dollar company. Some stocks seen as AI winners – such as semiconductor makers and software developers – have more than doubled in value as traders bet on massive growth in the industry, even as fears mount over waves of job losses as everyday tasks become automated. On Friday, the combined value of technology companies listed on the Nasdaq Composite share index reached $22tn, according to the international data firm Refinitiv, up from $18tn at the end of 2022. The AI rally has helped lift the index 23% so far this year. Nvidia, whose high-end chips are used to power the datacentres used by the new wave of generative AI products such as ChatGPT, could soon become the first chipmaker to be valued at more than $1tn.

UBS is testing out artificial intelligence (AI) to see if it can assist clients in how best to invest their money – just by looking at their facial expressions. UBS chief investment officer Mark Haefele says the Swiss bank is running several pilot programmes – with one tool able to interpret clients' facial expressions while they watch a video on financial planning. "This helps uncover biases," Haefele says. "You can say, 'Look, you said your biggest interest is planning for the long term but this artificial intelligence is showing us what you're really excited about are short-term trading ideas.'" This may not get down well with customers – who wants to be contradicted about what they're thinking?