Virtual assistants such as the iPhone's Siri are now everywhere, reading us the news, recommending restaurants and navigating a path to our jobs. But any casual user knows they're far from perfect. This week, Bloomberg Technology's Aki Ito and Alistair Barr visit Professor Terry Winograd, a pioneer in artificial intelligence who amazed the world with a precursor to these assistants half a century ago. Terry tests the assistants from Apple, Google, Microsoft and Amazon and explains why, despite all the hype, computer scientists are still far away from building machines that can outsmart humans.

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