Tim Cook doesn't spend his days reviewing resumes — but in his 11-year stint as Apple's CEO, he's determined what it takes to thrive at the company.  

At University of Naples Federico II's commencement ceremony this week, Cook told graduates from the Naples, Italy, university that he noticed Apple's success depends on its culture and who it hires. For instance, the company typically seeks out employees with four shared skills: the ability to collaborate, creativity, curiosity and expertise.  

"It's been a very good formula for us," he said, noting those traits also contribute to an ambitious, yet supportive workplace culture. "It's not like somebody goes in a corner or closet and figures out [how to build technology] by themselves."

As he spoke, he appeared to rank the skill sets in that order. He said the reason collaboration is so important is because it combines all three of the other skills.

"We look for… the fundamental feeling that if I share my idea with you, that that idea will grow and get bigger and get better," Cook said. "And that [collaborative] process is how Apple creates products."

That sense of teamwork lends itself to creativity and curiosity, as all three are needed to launch new or improve old ideas, he said.

"We look for people that think different — that can look at a problem and not be caught up in the dogma of how that problem has always been [solved]," he said. "It's a cliché, but there are no dumb questions. It's amazing when somebody starts to ask questions as a kid would do."

But whether Apple's hiring tactics consistently ensure a positive working environment is up for debate. This year, the company dropped off Comparably's annual list of global companies with the best workplace culture. It also received a "C" rating for office culture, despite ranking at No. 14 last year.

It also dropped more than 20 spots on Glassdoor's yearly ranking of best places to work in the U.S., plummeting from No. 31 to No. 56. Employee reviews on both sites cited poor work-life balance, erratic schedules and high stress from a competitive working environment.

"We are and have always been deeply committed to creating and maintaining a positive and inclusive workplace," Apple said in a statement to the New York Times, responding to employee complaints about a "toxic" culture that surfaced in September. "We take all concerns seriously and we thoroughly investigate whenever a concern is raised and, out of respect for the privacy of any individuals involved we do not discuss specific employee matters."

Apple's hiring tactic has been in place for at least six years, according to Cook. At the Utah Tech Tour in October 2016, Cook said Apple looked for brilliance, determination, obsessive curiosity, team focus and agitated idealism in its employees.

"We look for wicked smart people … [but] there are a lot of wicked smart people," he said at the conference. "We look for people that are very collaborative because nobody — even somebody who has … a cape on their back — can do everything alone."

CNBC