Computers are very good at doing dumb tasks rapidly, but they have a very hard time doing a lot of stuff that we find quite easy, says Google's Chewy Trewhella. "We speak as second nature, we can recognise images. Computers struggle with this. And translation - learning how language is structured - computers are not very good at that... It's that holy grail of artificial intelligence, actually teaching a computer to act like a human being."
With both Nuance and Google, voice technology is only possible at the moment on smartphone devices thanks to cloud computing, which means that when there's no internet connection, there's no functionality.
Steve Cramoysan, research director from technology analysts Gartner, says this is one of the big challenges facing the technology. "A huge vocabulary means you can't physically store it - you have memory limitations on the smartphone, so the phone is dependent on the cloud [to store the data]."
"Every year people say - voice is going to take off, it's going to be the year of voice recognition. I've been through this too many times to say this is the year."