One afternoon during Labor Day weekend, a group of 15 or so Yale freshmen met in a classroom where history and French classes would soon be held. As they snacked on pretzels and Skittles, a few volunteered to act out a series of scenarios in which one student asks another out for frozen yogurt. In the first bit of role playing, one student was told to make it clear, in an easygoing way, that he or she wants to go out. The recipient of the invitation was told that he or she also wants to go but has a paper due. “How can you show enthusiasm while still turning down the invitation?” a prompt on a card asked. The answer generally wasn’t hard to convey or, for the freshmen watching, to interpret. Most students found that they knew how to demur while keeping the door open for next time.

In the second scenario, the stakes rose. Now the inviter must get the other person to the frozen-­yogurt shop. And the invitee does not want to go, although — like most of us — he or she doesn’t want to be rude. “How would your character handle this unwanted invitation?” the second card read. The interaction made everyone in the room uncomfortable, as the inviter grew increasingly persistent and the invitee tried to fend the other off.

The intended lesson of this 90-minute workshop was that the line between a request and a demand, welcome interest and unwanted pressure, is usually fairly obvious. “This is the skill set people hammer out as little kids,” says Melanie Boyd, an assistant dean of student affairs. She wants students to realize that they know how to recognize agreement, refusal and ambiguity.

The workshop reinforced policies, newly adopted by a growing number of universities, requiring students to make sure they have continuing affirmative consent for every phase of a sexual encounter. The policies, many of which have gone into effect in the last year, were created to help clarify internal university investigations of sexual-assault accusations. In the past, the main question was whether the person (usually a woman) who claimed that she was raped had made it clear that she said no (“No means no”). The new rule shifts the inquiry to whether the student accused of assault got a signal of consent (“Yes means yes”). In California, Gov. Jerry Brown recently signed an affirmative-consent bill, making “yes means yes” the standard at the state’s colleges and universities. To continue to receive state funds for student financial aid, California institutions investigating allegations of sexual assault must determine whether both parties gave “affirmative, conscious and voluntary agreement.” Lack of resistance and silence no longer constitute proof of consent.