Emotient’s technology is primarily sold to advertisers to help assess viewer reactions to adverts, while it has also been used in retail to monitor shoppers’ facial expressions in-store.
An Apple spokeswoman confirmed the acquisition to the Wall Street Journal, but declined to comment on the terms of the deal or how Apple would use the technology.
Microsoft’s Kinect motion sensing technology has been used in the past to gauge reactions to adverts, but Microsoft is now beginning to sell the Xbox One without Kinect technology.
Apple buying an artificial intelligence firm comes as the tech giants begin to place the technology at the forefront of their strategy.
Google acquired London-based artificial intelligence firm DeepMind in 2014, while Facebook founder Mark Zuckerberg revealed he was creating an artificial intelligence butler for the home.
Emotient is based in San Diego had has raised $8m from investors including Intel Capital.
A source told the Wall Street Journal the company had been seeking a new round of venture-capital financing, but was unable to secure it on favourable terms.
Apple has already explored the possibilities of artificial intelligence and in 2014 it filed a patent application for a software system analyses people’s moods based on clues such as facial expressions.