In June, we found a trend in Apple's ($AAPL) hiring data that indicated the company was getting serious about making its digital assistant, Siri, smarter. At the time, we saw a jump in open positions with the term "Siri" in their titles, which led us to predict that Apple was setting its sights on building a vast team of engineers and scientists to bring Siri up to par with other digital assistants from Google and Amazon.

Just a few days after our story, Apple poached Google's former head of search and artificial intelligence to kick Siri's smarts into high gear. But Apple isn't done; it seems the company is continuing to build its team of artificial intelligence engineering teams to bring Siri's capabilities up to speed.

Of the 167 open positions on September 24, the most common titles — at least those that match perfectly — are for Software Engineers, with 6 openings. Of course, software engineers could be working on anything, but almost as common are NLP Research Scientists.

Title Title (Count) Siri - Software Engineer 6 Siri - NLP Research Scientist 4 Siri - Quality Engineer 3 Siri - Search/Domains Backend Software Engineer 3 Siri - Machine Learning Engineer, Proactive Intelligence 2 Siri - NL Tools and Infrastructure Engineer 2 Siri - EPM -Machine Learning & Data Science Search 2 Siri - Machine Learning Scientist 2 Siri - Language Modeling Scientist 2 Siri - Natural Language Processing Scientist/Engineer 2 Siri - Full Stack Engineer, Data & Analytics organization 2 Siri - iOS Engineer 2 Siri - Quality Engineer, Core Client 2 Siri - Machine Learning Engineer 2 Siri - UI Web Developer 2 Siri - Software Engineer (Siri Rotational Program) 2 Siri - Data Scientist (Machine Learning & Natural Language) 2 Siri - Software Engineer, Sports 2

NLP — natural language processing — is technology that allows digital assistants like Siri or Alexa to hear, parse, and understand naturally spoken language. It is, in essence, the core interface technology for Siri, so it follows that Apple would be focused on hiring experts in the field. In fact, the company is also looking for Natural Language Processing Scientists to help process whatever SIri hears.

The next level, or step, for Siri — or any nascent AI — is the ability to learn from experience, either that of users' behavior patterns or from a larger database. Apple has been building its deep-learning and machine-learning capabilities as of late, as we reported a month ago. Based on today's hiring data, it's clear the company remains focused on fleshing out this capacity as part of its long-term Siri plans.