“Do you know what ‘ttfn’ stands for?” I whipped around to see a lanky preteen girl browsing a rack of greeting cards with a friend. “No, what’s that?” asked the friend. “Ta ta for now,” the girl said. “People used to say it to text goodbye.” Her friend grunted an acknowledgment to this underwhelming trivia, the same way you might if you learned that you blink 10 million times a year, or that Salt Lake City has the nation’s longest city blocks.

I thought about the last time I’d actually typed ttfn. I imagine it was at least 18 years ago, on my family’s Gateway desktop during the era of dial-up AOL. And then I realized I couldn’t remember the last time I said “g2g,” or even “bye,” in an online conversation. I asked some friends in a group chat if they ever say goodbye when chatting digitally. “They never really have a beginning. Do they also not have an end?” said my friend Dan. Another friend, Mitch, chimed in with a diagnosis: “It’s because we never go offline anymore.”

While digital chatting used to be tethered to a bulky desktop and modem, or at least a laptop with Wi-Fi, smartphones allow us to send messages whenever. As texting replaced AIM, we could be—and, let’s be real, have been—online all the time, constantly connected. A scroll through my recent texts, WhatsApp, Facebook, and Slack messages shows that the closest I’ve come to anything resembling a goodbye or a signoff with a friend was two weeks ago, while making plans for a friend to come over (“see ya soon!”) or when a friend would be away from their texts for at least a few days (“enjoy Zion!”). A goodbye is merited only if one plans to disappear into meatspace for a while. Everything else is one long, rolling conversation.

The implication is comforting: that your friends will always be there for you, literally at your fingertips. Forgoing the formalities of hello and goodbye implies a certain closeness. You can just jump into talking about Martha Stewart’s Instagram posts, complaining about public transit, or swap Clickhole articles. And there’s some evidence that people who text more tend to report feeling less lonely and closer to their friends.

A goodbye is merited only if one plans to disappear into meatspace for a while.

But, as anyone who’s ever sent a vulnerable text knows, it can be jarring to put a message out into the world and get nothing back, leaving a message hanging in a void until the next time the conversation picks up. The etiquette of texting is, of course, different than an in-person conversation, but it can still feel like your conversational partner’s silence means something. Did I say something weird? Or is she just busy? It can be even worse if you’re trying to date who you’re texting. Is a slow or nonexistent response a sign of disinterest, or did something horrible happen to him? (A friend of mine actually began searching the local obituaries five days after a guy she’d hit it off with abruptly stopped returning her texts.)

That’s just the way our brains work. Babies as young as a month old get upset if they’re having a social interaction and the other person suddenly goes silent and still-faced, a phenomenon observed over dozens of studies by child psychologists. As adults, we’re incredibly attuned to others while we’re talking, taking in the tiny cues that volley conversation back and forth and indicate how what we said has been received. When we try to apply the same rules to digital chatting, things get complicated. We try to negotiate the same kind of turn taking, but many of the cues we use to gauge whether a conversation is going well—or even just still going—are missing. That can be stressful.

Giovanna Mascheroni, a media sociologist at Università Cattolica del Sacro Cuore in Milan, has studied how teens negotiate the “perpetual contact” our phones have created. In a 2016 study, many respondents say they read into a lack of response. It’s especially confusing when your conversational medium tells you if someone is currently online, or has already read your messages, like the “read” labels in iMessage, the green dot by your name in Slack, or the blue tick mark on WhatsApp messages. “When WhatsApp introduced the blue tick [that shows when you’re online], that introduced a lot of anxiety,” she says. “[Teens] felt they had to reply in real time, and when they saw the other person reading the text but being very slow in replying, that created anxiety—especially if they were experimenting with romantic relationships.”

Michele, a 14-year-old boy in the study, said he’d rather get a harsh reply than be ignored. Giorgia, 16, explained a thought process I imagine many of us are familiar with: “Maybe this person was engaged in the conversation but suddenly had to do something else, like he had opened the message but afterwards he went away. … Then the girl starts making thousands of questions and she worries.” Giorgia longs for simpler days. “I think that before this feature existed, that says when someone has seen your message, things were better,” she told the researchers.

Mascheroni’s study was only descriptive and did not include quantitative measurements of those students’ well-being. In fact, it appears that there’s no research looking directly at how text response time weighs on us. But clues from other research indicate that we expect swift responses, and it is, at the very least, irritating to us when we don’t get what we what.

In a 2014 study, researchers at Western Washington University surveyed people between the ages of 18 and 68 about their opinions on cellphone etiquette, which included their expectations about text response time. As you might expect, who’s texting matters: In general, people expected significant others to text back faster than friends. Age also seems to be a factor; younger participants texted more often, expected a faster response from conversational partners, and grew annoyed at nonresponses more quickly. Still, among the broader pool of participants, the average response indicated an expectation for people to text back within the same day, and many reported that they would be irritated if they didn’t receive a response in that time frame. People younger than 35 thought one should text back somewhere between a few minutes and an hour.

True to a thirtysomething, I was marginally irritated when the friends in my group text took awhile to respond when I asked if they still messaged goodbye to people. Just a few minutes earlier, we’d all exchanged dozens of messages about a friend of a friend who’d just been cast on a reality show. Maybe people disappeared to eat dinner, or maybe my question just wasn’t interesting enough to merit a response. After a few responses trickled in, a friend teased: “Would you prefer that we say goodbye to you, Jane?”

Before I could respond, the conversation took a hard turn: A friend posted a picture of a bug she found in her house, and we all tried to identify it. I never quite got the closure I wanted from the conversation, but the upside is, I can always bring it up again in this roiling sea of endless chat.

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.