Apple has bought a San Diego startup working on artificial intelligence technology that analyzes facial expressions to detect emotions. Apple confirmed the news to The Wall Street Journal, giving the usual boilerplate statement that it "buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans." Details of the deal weren't disclosed.

Facial recognition is an area in which several major tech companies have interest, though it's not without controversy. Facebook decided against releasing its Moments photo app in Europe because of fears over privacy regulations, and Google Photos only offers its facial recognition feature in the US.

It's not immediately clear why Apple bought Emotient, which mostly sold its software to advertisers, but the company has made some other recent acquisitions that are likely complementary. Faceshift, a motion capture startup focused on facial analysis, and Perceptio, a company with deep-learning image recognition technology designed for mobile processors, are now also under Apple's umbrella.