I recently reached a milestone that caused me to reflect deeply on the trajectory of my life: my 50th birthday.

I am proud of the decades-long friendships I have maintained and to celebrate, I took a tour to spend time with some of my best friends in Boston, Newport, Charleston, SC, Amityville, NY and Copenhagen, Denmark.

Although I met people at the stations that I met at different times in my life, there is a common thread: over the years we have stayed in touch by talking on the phone (or via Zoom in the case of my Danish friend) and in person.

I suspect this is a typical Generation X experience – and I wonder if most Millennials and Gen Z will be able to maintain these lasting friendships without the aid of the old-fashioned telephone, since it is well known that younger generations do not like to use the phone and even suffer from what is known as phone anxiety.

This shift in norms and preferences raises important questions, especially because there is much we don’t know about the long-term impact of the shift in communication to social media, texting, and group chats.

As a child, I envied my friends who had their own phone number. You could call them directly instead of calling the family number and possibly having to talk to your parents or siblings. I couldn’t imagine that one day everyone I knew would have their own phone and take it everywhere. But for me, phone calls are still an important way to maintain close friendships.

Of course, being tied to a phone at work when you can’t control your own time can be brutal and demoralizing. But when it comes to social interaction, phones are a symbol of caring for me. Decent phone calls take more time and emotional energy than liking a post, writing a comment, or sending a quick text or DM, and they require a willingness to be there at the same time as your friend. In a time when our attention is constantly divided, being present is one of the greatest gifts we can give. One sign of a good friend is that the person takes your unplanned call—that they’re willing to give you their time and not limit interaction with you to moments that work best for them.

And then there’s the medium, which can foster a close connection in two ways. On a phone call, the other person’s voice conveys emotion and can evoke strong memories and feelings associated with face-to-face interactions. Additionally, because calls are more private – at least when no one is within earshot – than public and semi-public social media interactions or group messages, they reduce the pressure to be socially active and provide a space to speak your mind.

In a 2021 psychological study, researchers examined the impact of text and voice on social connections, testing how people would feel about reconnecting with an old friend via email or phone. Most participants preferred email because they expected the medium to make the conversation less awkward. The researchers then divided participants into groups: Some called to reconnect and others used email. Participants who used the phone felt more connected than those who used email—and they surprised themselves by saying they “didn’t feel significantly more uncomfortable” than those who communicated via email.

The deep connection between presence and intimacy explains why I prefer to talk to my friends one-on-one and rarely engage in group conversations. The shared space of undivided attention encourages active listening, and that is a key element of what Aristotle called the best kind of friendship: a friendship rooted in concern for each other’s well-being.

Relationships of this kind, which Aristotle called “virtue friendships,” are far more important and tend to last longer than friendships with people who share your interests or are useful to you professionally. You can’t have many friends in this category, because being there for them and genuinely interested in their lives and concerns takes a lot of bandwidth. You have to commit to making them a priority – which in today’s hyper-connected world means not allowing them to be drowned out by the people you have weak ties to who vie for your attention on your social media feeds.

The true measure of a person’s social network is not its size, but its ability to cultivate and maintain those rare Aristotelian virtue friendships. Don’t underestimate the phone’s ability to help you cultivate those friendships.

Evan Selinger is a professor of philosophy at the Rochester Institute of Technology and a regular writer for Globe Ideas.