The founder of design firm IDEO David Kelley has spoken about his friendship with Apple's late co-founder Steve Jobs in an interview about the philosophy behind 'design thinking'.

Kelley was part of the team that helped design Apple's first mouse, the Apple III and the Apple Lisa, and was close friends for more than 30 years with Jobs, who he met after studying product design at Stanford.

The key to design thinking is empathy and observation, Kelley explained, describing the process IDEO goes through in order to come up with innovative product design. "Be empathetic," Kelley told CBS' Charlie Rose during the interview with 60 Minutes. "Try to understand what people really value… If you want to improve a piece of software, all you've got to do is watch people using it."

By using a team of people from different walks of life, you can come up with ideas by building on the ideas of others. "You get to a place that you just can't get to in one mind."

Kelley said that Jobs "made" IDEO, because he was such a good client. Jobs would call Kelley at 3am to discuss his design thoughts. "He was deep into every aspect of things," Kelley said.

For example, when designing Apple's first mouse, Kelley and his team at IDEO had to make many changes to the product to suit Jobs' high expectations. "He didn't like the way the ball sounded on the table, so we had to rubberise the ball," said Kelley.

But, despite being picky, Kelley insisted that Jobs was not malicious, explaining that the biggest misconception about Apple's co-founder was that he was trying to be mean to people. "He wasn't," Kelley said. "He was just trying to get things done."

Jobs was the man who introduced Kelley to his now wife, and also provided support when Kelley was suffering from a life threatening throat cancer, giving him advice based on his own battle with pancreatic cancer.

Jobs urged Kelley to go straight to Western treatment and focus on spending time with his family, rather than seek alternative cures as he did. "In his mind, he had made a mistake," Kelley said.

Kelley took Jobs' advice, and while he was home and undergoing treatment, was surprised by a visit from Jobs the day after the first iPhone was launched in 2007, who gave Kelley very own iPhone.

Jobs even offered to call US carrier AT&T to help Kelley set up his new iPhone, but this proved difficult to achieve. "Eventually he pulls the 'I'm Steve Jobs' card. And I'm sure the guy on the other end said, "yeah buddy, and I'm Napoleon," Kelley joked.

'jOBS', a film starring Ashton Kutcher that depicts Steve Jobs' early life at Apple, is set to arrive in cinemas in April, and will be the first movie released about Jobs following his death in October 2011.

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