The 'Who You Love' hitmaker, who split from the singer last month, has praised her work ethic and spoken about the reason women often decide to get back with their ex-boyfriends.
He told America's Sirius Radio: ''It is a connection to the past, a reaction to fear of the unknown. They go back with a guy they don't like just because they know how to get to his bathroom in the dark.''
The 36-year-old star, who had an on/off relationship with Katy from 2012, went on to gush about the 'Dark Horse' singer, who is in Sydney, Australia promoting her upcoming Prismatic world tour.
He said: ''She's extremely driven and extremely serious about doing great work.''
Katy, 29, reportedly broke up with John because he kept breaking promises and their conflicting schedules have made it difficult for them to continue their relationship.
A source said: ''The last time they broke up John won her back by making a ton of promises. He was going to put her first, but now he's falling back into his old patterns.
''Like, he shuts off his phone and disappears all day and night - he says it's because he needs alone time, but it's sketchy for sure.''
Katy was left heartbroken when her marriage to Russell Brand ended after 14 months in December 2011 and she ''isn't willing to put up with any shenanigans'' from men.
Meanwhile, John has already been spotted with a mystery brunette during a night out at the Sunset Tower in West Hollywood on Saturday (01.03.14), just days after splitting from Katy.
Celebrating the gothic rock movement of the 80s and beyond.
On their self-titled debut album, it's really game time for jazz rappers Injury Reserve.
Celine Dion barely cracks a smile and yet she's the greatest guest yet.
Add this guy to your playlist ASAP.
Phildel has gone back a step, in terms of her musical compositions, and returned to a style more reminiscent of her debut album with her latest...
To promote the release of her latest album 'Designer', Aldous Harding has undertaken an extensive European tour. On Wednesday night Harding played to...
Injury Reserve have spent the last few years rising to the top of underground hip-hop and becoming one of the most exciting acts in the whole genre.
Audiences may be divided over whether this comedy crosses the line as it looks for...