The boss of language learning app Duolingo has revealed that chauffeurs are paid to secretly assess job applicants on the way to their interviews.

Drivers report on how the candidate speaks to them in the 'taxi test', and that feeds into the hiring decision.

Chief executive Luis von Ahn said: 'Part of the interview for us is how they treated their driver.

'Our belief is if they are gonna be mean to their driver they are probably gonna be to other people, particularly under them, so we did not want that.'

Mr von Ahn told The Burnouts podcast that a candidate for the role of chief financial officer at the company was 'really liked' in the interview and had an impressive CV.

However they were rejected for the job as 'it turned out they were pretty mean to their driver from the airport to the office [and] that made us not hire them'.

The billionaire CEO said elsewhere during the interview that it's important the right person is hired for the job as the company has leaned into artificial intelligence, saying last April he was replacing contract employees with the technology. 

However last June he clarified that while AI will not replace jobs, employees will be required to adjust the way they work. 

In a LinkedIn post Mr von Ahn said the technology will 'fundamentally change the way we work - and we have to get ahead of it'.

He said: 'To be clear: I do not see AI as replacing what our employees do (we are in fact continuing to hire at the same speed as before). 

'I see it as a tool to accelerate what we do, at the same or better level of quality. And the sooner we learn how to use it, and use it responsibly, the better off we will be in the long run.' 

Speaking on the Duolingo chief executive's unconventional hiring method, a taxi driver union boss has said the test was a good idea - as cabbies are always 'quickly able to get a flavour for people'. 

Steve McNamara, general secretary of the UK's Licensed Taxi Drivers Association, told The Times: 'One presumes that they are a little bit nervous and apprehensive as everybody is when they go to an interview but if you're not nice when stressed, and you're gonna be stressed a lot of time in some of these high-profile jobs, then maybe the job's not for you.' 

He added that candidates are also more likely to be honest with taxi drivers than with their potential future bosses during job interviews. 

'We used to call the cab a confessional booth. People tell you things in a cab that they would never tell a stranger in real life, or would never tell other people,' Mr McNamara said. 

'So you'll get in my cab, I'll quickly learn that you've had enough of your wife and you're thinking of running off with the nanny.' 

A Duolingo spokesperson told the Daily Mail: 'At Duolingo, we care about character, not just credentials. We hire people who are both excellent at what they do and kind to the people around them.

'For senior in-person interviews, we arrange car services for candidates, and how someone treats the driver is something we pay attention to. This is one of several ways we assess whether someone's a good fit.'