Siri co-founder leaves Apple following iPhone 4S launch

Dag Kittlaus left his position at Apple after the launch of the iPhone 4S, according to Kara Swisher of All Things D. He served as CEO of Siri since 2007, and after the company was acquired by Apple in April of 2010, he led its speech recognition development.

"There were several reasons for the departure, which was amicable and has been planned for a while, sources said," Swisher wrote. "They included Kittlaus' family being in Chicago, a desire to take time off and an interest in brainstorming new entrepreneurial ideas."

His LinkedIn profile still lists his current title as director of Siri and speech recognition for iOS at Apple in the San Francisco Bay area. The other titles he currently holds are a member of the Cabrini Green Tutoring Program Board of Directors, and a founding advisor at Palindrome Advisors. He was previously an entrepreneur-in-residence at Stanford Research Institute, and a general manager at Motorola.

Siri technology is one of the main selling points of the iPhone 4S, Apple's latest smartphone model that launched earlier this month. Using natural language, users can have their phone do complex tasks like send a text message or e-mail, make or modify a calendar appointment, set reminders or alarms, or even look up information like the date of the next full moon.

Swisher said that Kittlaus departed Apple just after the launch of the iPhone 4S. Sources told her that other key executives from Siri are expected to remain with the iPhone maker.

After the iPhone 4S and its Siri voice control were unveiled on Oct. 4, Kittlaus was finally capable of speaking publicly about his work on Siri at Apple. He immediately took to Twitter that same day.

"If you are a start-up you want to get acquired by Apple," he wrote. "Fun times."

Though the Siri brand remains with the voice recognition technology found in the iPhone 4S, it is believed that Apple's implementation also uses intellectual property licensed from Nuance Communications, makers of Dragon NaturallySpeaking. Neither Apple nor Nuance have confirmed that Nuance's technology plays a part in Siri on the iPhone 4S.