Even if you don’t believe in love at first sight, chances are that you’re familiar with lust at first sight. There are some people that, for some unexplainable reason, you’re just magnetically drawn to—regardless of whether or not they look like Zoë Kravitz or Timothée Chalamet.

Often, it’s the lack of an immediate spark that stops many from going on a second, third, or fourth date with someone. Not having chemistry is a common complaint for many daters; even if a potential partner looks good on paper (so to speak), a lack of chemistry will likely be a deal-breaker.

To help explain the science of attraction—and what determines if you have chemistry with someone or not—New York relationship and sex therapistMichael DeMarco, PhD, and Three Day Rule matchmaker Lisa Elson share their expert insights. Plus, when to know if a lack of chemistry should be a deal breaker.

Understanding the science of attraction—and how it’s different from chemistry

Elson says many people think of attraction and chemistry as the same and use the terms interchangeably, but that’s not quite accurate. “A lot of people, when they go on a date, they want to feel those butterflies and excitement. But you don’t want to confuse getting butterflies with thinking you found your soulmate,” she says.

According to Elson, there can be many reasons why someone feels those butterflies, aka attraction, that have nothing to do with actual chemistry. For example, a feeling of slight danger can cause butterflies, or even recognizing traits of someone you dated in the past. “Someone may get butterflies as an internal response to something familiar, such as if a current date is portraying behaviors of an ex,” she says. “But that doesn’t mean it’s good.”

Excitement can often be interpreted as attraction, adds Dr. Marco. “As humans, we’re wired for novelty,” he says—so meeting someone new can trigger feelings of excitement and “butterflies,” so to speak. He also adds that hormones come into play too. “When it comes to the science of attraction, a hormonal cascade happens,” he says. “If you’re horny, your brain produces testosterone or estrogen, which can lead to desire.” Dr. Demarco also points to oxytocin, which is released during sex and is often referred to as the “bonding” hormone because it can lead to feelings of attachment. It’s one reason why you may feel connected to someone you’re sleeping with, even if you don’t seem to have anything in common.

Now that you know what plays into attraction, what about chemistry? Elson says chemistry is more linked to compatibility; it’s about what you have in common, such as shared interests and values. “That’s what’s going to build long-term chemistry,” Elson says. Dr. DeMarco refers to this type of chemistry as intimacy, which he says is built over time and not immediate. “Those initial butterflies may fade, but this type of chemistry—compatibility and intimacy—is what will last longer,” he says.

If you’re looking for lifelong love, both experts say compatibility is the more important factor here, but Dr. Demarco points out that just because you do have initial butterflies or attraction for someone, it certainly isn’t bad. “An element of common sense comes into play here when you think about what may be causing your excitement, but you have to wait and see until you get to know the person better to see if you have compatibility as well as attraction,” he says.

Chemistry can lead to attraction

Both experts also say that attraction isn’t always immediate; sometimes it develops after you get to know someone. “One study by Match.com found that 35 percent of American singles experienced zero attraction on a first date and then later report falling madly in love,” Elson says. “If you don’t feel that initial attraction early on, it can build.”

Dr. Demarco also points out that dates that get your heart racing—like going to an amusement park together—can also increase attraction, due to the same reason that a small dose of danger can cause butterflies. He also reiterates that because humans are wired for novelty, trying something new together can increase attraction, too.

When it comes to whether or not you should see someone again if there’s a lack of attraction, Dr. Demarco says it depends on what you’re looking for; after all, not everyone is looking for a long-term partner. But if you are looking for long-lasting love, both experts say focusing on what you have in common is more important than initial attraction. “As a matchmaker, I feel like a broken record repeating myself so often about giving people a chance,” Elson says. “We live in this world of instant gratification, but the right person is out there. You just have to give them a chance and don’t give up on something that could turn out to be really good.”

Here’s how to know if you’re actually in love, or if it’s just your hormones. Plus, what to do if you find yourself falling out of love.