Ever wondered why certain friends' posts appear at the top of your Instagram feed?

Well, the reason isn't solely down to the fact that you might have liked their Insta posts a few times. Your Facebook activity also influences whose content is prioritised in your feed.

Now that our Instagram feeds are no longer arranged by chronological order, our feeds now use something called 'feed ranking' to show us content from people we are close to.

Mashable spoke to Instagram Design Lead Jill Nussbaum and Product Lead Julian Gutman about how our feeds work.

Nussbaum said the reason the feed is no longer ordered chronologically is because people were missing posts from the people they care about.

"One of the main reasons was people were missing the posts that mattered to them," said Nussbaum. "So before we introduced ranking in 2016, people were missing 70 percent of their content. Over half of that content was friends and family."

In 2016, Instagram ditched chronological ordering and introduced "feed ranking" which prioritises posts that are "most important to you."

So, how exactly does Instagram know what matters to you? Well, it uses machine learning to analyse your data from your Instagram activity, according to Gutman.

"Feed ranking is powered by machine learning which is a technology that uses historical data to make predictions about the future," said Gutman. "And the way we use machine learning in feed ranking is we analyse people's historical Instagram usage to predict which of your posts are going to be most relevant to you."

Gutman added that machine learning is "constantly adapting and evolving over time" based on how you're using Instagram. So, that means your feed will continue to tailor itself to the accommodate new friends or new interest in pre-existing friends.

"We use a lot of signals to determine the posts that are most relevant to you," Gutman added. Some of those "signals" include things like "how likely are you to be interested in that content," in addition to how recent the content was posted, and how close you are to the author of the content.

So, how exactly does Instagram work out how close you are to certain people? Do our interactions on Facebook play a part in this?

"We use Facebook data to tailor's people's experience in a couple of ways," Gutman said.

When asked, Gutman didn't give any specifics about what those signals might be, but did say that being friends with someone on Facebook is "one of the factors in terms of understanding your relationship."

He added that those signals comprise "different ways that you might express your intent in terms of how that person matters to you" on both Facebook and Instagram — so make of that what you will.

"We've kind of learnt over time which signals are more important than others," he added.