The iconic television series Sex and the City popularized the idea of the "three date rule"—the idea that, when it comes to sex, there's supposed to be a short waiting period. The goal is to give you a chance to evaluate the other person before hopping into bed. Plus, you don't want to give the other person the impression that you're over-eager, but you also don't want to wait too long to start having sex in case it turns out you're incompatible.

This "rule" is basically the Goldilocks approach to dating: It's about figuring out the time to have sex that's "just right." Is there any scientific backing for this idea, though? And is the third date really when most people start having sex anyway?

Believe it or not, social scientists haven't yet established which specific date is the most common one for people to start having sex, in part, because "date" is a pretty nebulous term. What counts as going on a date anyway? For example, does it have to be one-on-one, or can going out with a group of friends count, too? Also, how is "dating" different from "talking" or "hanging out" with someone?

Even if people could agree on a definition, the number of dates isn't all that meaningful to look at because people space them out very differently. Some people go on several dates in the same week, whereas others space them out over a month or more. In other words, two couples could be on their third date, but one pair might have known each other a lot longer than the other.

In order to get around these issues, researchers who study this topic have focused more on the length of time people have known each other rather than on how many dates they've had.

A study published in the Journal of Sex Research of nearly 11,000 unmarried adults who were in "serious or steady" relationships inquired about when participants started having sex and looked at how this was related to their relationship satisfaction. Most participants (76 percent) had been in their relationships for more than one year, and nearly all of them (93 percent) reported having had sex with their partners.

Of those who were sexually active, a slight majority (51 percent) said they waited a few weeks before having sex, while just over one-third (38 percent) had sex either on the first date or within the first couple of weeks. The remaining 11 percent had sex before they even went on their first date.

Did the timing of sex matter in terms of how people felt about their relationships? Not in a meaningful way. There were only small differences between the groups, with those who had sex earlier tending to be slightly less satisfied. However, all of the groups were highly satisfied on average.

The fact that those who had sex earlier were a little less happy is to be expected based on research showing that sexual passion and excitement This link (www.lehmiller.com) is not approved. Submit this link for approval over the course of a relationship. So if you start having sex sooner, the passion will wear off a little faster, unless you put in the work to keep it going (which you can do by This link (www.lehmiller.com) is not approved. Submit this link for approval in the bedroom).

There's something far more important than when you start having sex, and that's what your personality says about how sex and love go together. Everyone has what's called a sociosexual orientation, which is basically the degree to which you think sex and emotions are intertwined versus totally separate.

People who think that they go together tend to agree with statements like, "I do not want to have sex with a person until I am sure that we will have a long-term, serious relationship." These folks have what psychologists call a "restricted" orientation.

By contrast, people who think that these things are separable tend to agree with statements like "sex without love is OK." These people have what psychologists refer to as an "unrestricted" orientation. Unrestricted people are more comfortable with casual sex, and they tend to report higher sex drives and greater numbers of sex partners over the course of their lives. As a result, the amount of time it takes for them to be comfortable having sex with a new partner is much shorter than it is for someone with a restricted orientation.

Neither orientation is inherently better or worse than the other, but knowing where you fall on this trait will give you insight into whether having sex sooner or later is the right approach for you. Understanding differences in sociosexual orientation can also help us to understand why so many couples disagree on the "right" time to start having sex as well as how much sex they should be having—if you put a restricted and an unrestricted person together, it might be challenging for them to get on the same page.

What all of this tells us is that there are no hard and fast "rules" for dating. Different things work well for different people depending on their personalities, so figure out where your comfort zone is—and your partner's, too—rather than subscribing to some arbitrary rule.