United Kingdom, June 6 -- Dakota Johnson sent gorilla poop to a friend's ex-boyfriend.

The Materialists actress admitted she sought out an unusual way of getting revenge on the mystery man when her unnamed pal was left with a broken heart.

In a lie detector test with Vanity Fair magazine, the 35-year-old star was quizzed about her loyalty and admitted she would lie to police about her "lifelong" friend Riley Keough's alibi if need be.

She was then asked to confirm whether or not she "once sent a man who broke your friend's heart a gallon of gorilla s***."

She admitted: "I mean, there's no way that he would watch this, so, yes, I did do that...

"And it's been quite a while. It's been some years."

The interrogator then asked: "How wou...