Some teenagers and "truckers" who do not have partners are also developing feelings for female and male-voiced chatbots such as Siri, one expert said. 

Ilya Eckstein, the chief executive of Robin Labs, said his company's virtual assistant - Robin - was used by some men for up to 300 conversations a day. 

He told The Times it was "mostly teenagers and truckers without girlfriends" who were turning to the virtual world.

"This happens because people are lonely and bored.... It is a symptom of our society," he said. "As well as the people who want to talk dirty, there are men who want a deeper sort of relationship or companionship."

He added to Quartz that people who use engage with their virtual assistants in such a way "want to flirt, they want to dream about a subservient girlfriend, or even a sexual slave".