NEW YORK — Facebook likes can tell a lot about a person. Maybe even enough to fuel a voter-manipulation effort like the one a Trump-affiliated data-mining firm stands accused of — and which Facebook may have enabled.

The social network is now under fire after The New York Times and The Guardian newspaper reported that former Trump campaign consultant Cambridge Analytica used data inappropriately obtained from roughly 50 million Facebook users to try to influence elections. Among that information were users’ likes.

Facebook stock plunged 7 percent in trading Monday. The head of the EU parliament has promised an investigation. U.S. congressional members and Connecticut’s attorney general are seeking testimony or written responses. After two years of failing to disclose the harvesting, Facebook said Monday that it hired an outside firm to audit Cambridge Analytica and its activities.

What’s not clear, though, is exactly how effective Cambridge’s techniques are.

Researchers in a 2013 study found that Facebook likes on hobbies, interests and other attributes can predict a lot about people, including sexual orientation and political affiliation. Computers analyze the data to look for patterns that might not be obvious, such as curly fries pointing to higher intelligence.

Chris Wylie, a Cambridge co-founder who left in 2014, said the firm used such techniques to learn about individuals and create an information cocoon to change their perceptions. In doing so, he said, the firm “took fake news to the next level.”

“This is based on an idea called ‘informational dominance,’ which is the idea that if you can capture every channel of information around a person and then inject content around them, you can change their perception of what’s actually happening,” Wylie said Monday on NBC’s “Today.”

Late Friday, Facebook said Cambridge improperly obtained information from 270,000 people who downloaded an app described as a personality test. Those people agreed to share data with the app for research — not for political targeting. And the data included who their Facebook friends were and what they liked — even though those friends hadn’t downloaded the app or given explicit consent.

During the 2016 presidential elections, Cambridge worked both for the primary campaign of Texas Republican Sen. Ted Cruz and President Donald Trump’s general-election campaign. Trump’s campaign paid Cambridge more than $6 million, according to federal election records, although officials have more recently played down that work.

Cambridge was backed by conservative billionaire Richard Mercer, and employed Stephen Bannon, who later was Trump’s campaign chairman and White House adviser.