With Reporting by Josh Horowitz

How much can a person change between their early and late 20s? Quite a lot, actually, to hear Amanda Seyfried tell it.

Seyfried stars in the new Ben Stiller movie "While We're Young," about a middle-aged couple who experience something of a crisis upon making contact with a younger pair. While Seyfried is far from middle-age, she's also far from some of the more careless trappings that many people in their early 20s find themselves caught up in.

In a conversation with MTV, Seyfried, who turns 30 later this year, said that people who are even just a few years younger than she is can find themselves making tricky decisions, justifying their actions without thinking about consequences — especially where dating's concerned.

"You can date a douche bag, or somebody who is involved with somebody else," she said. "You shouldn't, but you give yourself excuses. There's never a time and place for a lot of those things that you justify when you're younger."

But, she adds, a lot of these bad choices are all part of informing how a person grows up and moves forward.

"It's all in growing up and making mistakes," she said. "You think about the consequences. You really, really consider the consequences."

"While We're Young" opens in theaters this weekend.