It takes less than 20 minutes for the average American to know if they want a second date, according to new research.

The survey of 2,000 single Americans (who are dating and/or looking for a partner) revealed the average respondent knows whether or not they’d like to see someone again at the 19-minute mark of their first date.

That may vary by age, too, as older respondents have higher standards for a potential partner — 67% of Gen Zers said they have high standards, while 77% of Gen X said the same.

When it comes to the date itself, physical appearance is important to 44% of respondents, but a greater value is placed on manners (51%), personality (48%) and conversational skills (47%).

Commissioned by Avocado Green Mattress and conducted by OnePoll, results found that while conversational skills are valued, the specific topics of conversation can be a red flag.

Results found 53% would be turned off if someone brought up sex on a first date, with younger respondents more likely to agree (56% of Gen Z vs. 39% of Gen X).

Religion and exes were also revealed to be taboo topics for a first date, with about half the panel finding them to be a red flag (51% and 47% respectively).

The survey looked beyond first dates and delved into partner compatibility, especially when it comes to sustainability.

Seventy-four percent of respondents are more likely to go on a first date with someone if they’re thought to be sustainable. And 44% have discussed environmental issues while on a first date.

The survey found 82% think it’s important to have a sustainable partner, and 76% find being environmentally friendly an attractive trait in a partner.

“Sustainability is sexy,” said Jessica Hann, Avocado’s Senior Vice President of Brand Marketing and Sustainability. “It’s an important core value, and sharing values is essential to compatibility and seeing a future with someone.”

Seventy-two percent of respondents believe when couples have a shared commitment to sustainability, they’re more likely to have a successful relationship.

But the survey also found that 43% of respondents have “eco-shamed” their partner — calling them out for wasteful or environmentally-unfriendly behavior.

And despite people seeking out sustainable partners, the survey also revealed that 45% have caught their partner sneakily doing something that isn’t eco-friendly.

“Nobody likes a greenwasher,” said Hann. “It’s on each of us to follow through and make the choices that actually support our values — like taking care of our planet.”