Game of Thrones tends to make your pulse quicken — but now we know exactly which moments in the show are the most thrilling. Spoiler alert: nearly all of them are about character interactions, not big battle scenes.

The Apple Watch app Cardiogram, which has previously been able to warn users about early signs of heart disease, has turned its attention to HBO's most popular show in a bid to discover what it does to our heart rate.

Cardiogram got 300 users to sign up for a "What Game of Thrones does to your heart rate" habit, which reminds them to start recording their heart rate every 5 seconds (the Apple Watch default is every 5 minutes) at 8:45pm on Sundays. From those 300 brave guinea pigs, it gathered a total of 2.3 million heart rate measurements.

As you can see from this anonymous example, even the anticipation of a new episode can get our hearts racing:

omg omg new 'Game of Thrones' omg Image: cardiogram

Once Cardiogram knows that people are watching, it can link spikes in heart rate activity to particular scenes. Its conclusion? "The data confirms that drama rather than action is what makes Game of Thrones viewers' heart rate race," says Cardiogram co-founder Brandon Ballinger.

Here are the top 5 most pulse-quickening moments in Game of Thrones Season 7 so far:

1. Jaime's charge against Daenerys and Drogon in Episode 4

Average heart rate: 91 beats per minute

Yes, we all got excited about the arrival of the dragon and the Dothraki. Our mouths dropped when Bronn's Scorpion struck Drogo. But we didn't really quicken our pulses until the final minute, when the main characters on both sides seemed headed for the worst kind of confrontation.

"This is the one action scene in the top five," Ballinger points out. "True to principle, it focuses on a conflict between two main characters on opposite sides of a battle: Jaime Lannister and Daenerys Targaryen, immediately preceded by a scene showing Tyrion Lannister's internal conflict at seeing his family's army set aflame."

2. Arya Stark's revenge on House Frey in Episode 1

Average heart rate: 83.2 beats per minute

The opening scene of the entire season — in particular, Arya's "tell them Winter came for House Frey" drop-the-mic moment — seems to have spiked our heart rates more than any other non-action scene. Even if it did look like something out of Scooby Doo.

3. Tie: Euron Greyjoy's proposal to Cersei in Episode 1; Davos and Jon's plea to Daenerys in Episode 3

Average heart rate: 83 beats per minute

You wouldn't necessarily have placed either of these scenes in your top memories of the season. But it seems that Euron's offer of marriage to Queen Cersei got our hearts thumping, possibly because it involved embarrassing Jaime to his face.

Equally exciting was that first Dragonstone throne room confrontation between Dany and Jon. You may remember Ser Davos pointing out that if the two don't unite to fight the threat from the North, "it doesn't matter whose skeleton sits on the Iron Throne."

Was it the tension of Dany and Jon meeting for the first time? The fraught social situation? The possibility of conflict between Targaryan and Stark? The reminder of the White Walkers? Clearly more study is needed.

5. Daenerys turning on Varys in Episode 2

Average heart rate: 76 beats per minute

Out of the blue, Dany goes ballistic on one of her chief advisers for having served the King who usurped her father. Varys recovered — with an assist from Tyrion — but the incident left our pulses racing like few others.

Why? Perhaps this was the first moment we realized that Dany has a lot of the Mad King in her. Or perhaps, in our hearts, we all empathize with that nightmarish moment where the boss calls you out in front of the whole office and you have to think on your feet.

In short, Game of Thrones' most engaging moments appear to be about dialogue rather than the gruesome violence we might normally associate with the story.

Indeed, George R.R. Martin has often said he is guided by William Faulkner's dictum that "the only thing worth writing about is the human heart in conflict with itself."

When hearts are most in conflict on the screen, it turns out, so are the hearts in our ribcages.