Apple Inc. will hand over the supervision of its Siri team to new artificial intelligence chief John Giannandrea three months after hiring him from rival Google, transferring responsibility for voice assistant technology to its third leader in the last year .
Apple announced the hiring of Mr. Giannandrea internally in early April, but had not publicly exposed his responsibilities until Tuesday, when he added it to the corporate leadership page of his website. He said he will report directly to Chief Executive Tim Cook, with the title of head of machine learning and artificial intelligence strategy and an area that includes the development of Siri technologies.
Mr. Giannandrea takes control of Siri as she tries to fend off growing competition from rivals such as the Google Assistant of Alphabet Inc. and Alexa of Amazon.com Inc. Those voice aides have outperformed Apple's product in independent tests on their ability to answer questions accurately, forcing the iPhone manufacturer to catch up on a category that was pioneering.
Apple officially shifted Siri's responsibility to the software chief
last september It had been overseen by senior vice president Eddy Cue since 2012.
Voice-based virtual assistants like Siri and Alexa, powered by artificial intelligence technology, are gaining popularity by simplifying people's computing tasks, how to look for information, buy and turn on lights. Industry executives expect systems to be integrated into a range of devices, from vending machines to automobiles and appliances.
The number of Google Assistant and Alexa users has increased in recent years amid the growing popularity of smart speakers. The market is expected to reach 225 million units worldwide by 2020 with Amazon Echo and Google Home each claiming 34% of the market, according to market researcher Canalys.
Apple HomePod, which went on sale in February, has slowly faced sales after critics criticized Siri's limited capabilities on the device. Apple sold 600,000 speakers in February and March, according to a market study by Strategy Analytics, and is expected to claim only 10% of the global smart speaker market by 2020, according to Canalys.
Apple declined to comment on Mr. Giannandrea's role. The company has said that Siri is the most used virtual assistant in the world with more than 10 billion requests processed monthly.
At Google, Mr. Giannandrea, known to his colleagues as "JG", oversaw artificial intelligence and search. His responsibilities at Apple, in addition to Siri, will include running Apple's extensive machine learning efforts. The role gives him the opportunity to further integrate the machine learning tools developed by startups bought by Apple over the past two years, including Lattice and Turi Inc., to improve Siri's performance, analysts said.
It will also monitor what Apple calls its Core ML technology, a system that extends the company's machine learning capabilities to application developers.
Write to Tripp Mickle at Tripp.Mickle@wsj.com