Less than a week into 2016, and Apple already has made its first startup purchase of the year. The iPhone maker on Thursday acquired Emotient, a San Diego artificial intelligence specialist, the Wall Street Journal reports. Financial terms of the deal weren’t disclosed.

Emotient uses its AI technology to read the emotions on the faces of people, primarily for advertising and marketing purposes, such as measuring a customer’s response to ads and products. It adds to a growing string of artificial intelligence technology purchases Apple has made over the years.

In October, Apple acquired Perceptio, a startup that develops technology that enables smartphones to use artificial intelligence without the need to share data with a company’s servers, according to Bloomberg. That same month Apple bought out Britain's VocalIQ, a company working on voice-recognition tech that can interpret dialogue and natural language. It was purchased for a sum of between $50 million and $100 million dollars, according to Britain's Business Weekly.

A month earlier, Apple purchased FaceShift, a Swiss company that develops real-time facial motion capture technology, according to TechCrunch.

“Apple buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans,” a company representative told the Journal.

While it’s not clear exactly what it has in store for Emotient’s technology, Apple has explored the idea of reading facial expressions in the past. According to a patent application published last year, Apple considered a system that could deliver advertising and content to a user based on mood as read through facial expressions and heart rates.