SoftBank's human-like robot named Pepper poses for pictures in its role as a PR manager of Tottori prefecture at the prefecture specialty store in Tokyo, July 1, 2015.

Warnings that robots will eventually wipe out humans may seem like no more than science fiction, but the machines are increasingly encroaching on the jobs humans used to do, with many Americans expected to own one in 4 years' time.

One in ten American households will own a consumer robot by 2020, according to Juniper Research, up from 1 in 25 this year.

Juniper made it clear that the robot might not necessarily be a humanoid but more suited to performing a particular task. The research firm defined its version of a robot as an "autonomous, mobile electromechanical machine, capable of being programmed and re-programmed, that is used in the home or has non-commercial applications. It should be able to perceive its environment to some extent and react to it".