Should you’re on TikTok, you’ve probably come across the yearbook challenge. It’s when people post high-school yearbook photos of themselves and their friends after which flash forward to them in the current day, often at a marriage, ten-year and even 20-year reunion – to “Spirits” by The Strumbellas. These videos garner likes and views of their hundreds of thousands, proving just how obsessed we should not only with nostalgia and physical transformation but with the passage of time.

Yearbook challenges have only recently grow to be popular on TikTok, but the thought of glow-ups and posting old photos on social media has been around for some time. Whether you tagged your photos with #ThrowbackThursday and #FlashbackFriday or recreated old childhood pictures together with your now-grown siblings, the web has all the time encouraged us to reminisce about how we used to look.

After seeing other people do the yearbook challenge on TikTok, Jade Yamada decided to do it herself at her engagement party, where she knew all of her friends could be looking their best. Yamada has all the time stayed in close contact together with her highschool friends, so it made sense she would wish to reminisce about their past. “For us, it’s a lot fun to look back and reminisce on our memories because we now have had so many together. It’s interesting to look back at photos and take into consideration what you were going through on the time and the way far you’ve come,” she says.

With over 184,000 likes and a pair of,500 comments, Yamada was shocked by how much engagement her TikTok got. Although most viewers didn’t know her or her friends personally, they were still very interested and a few even commented about their favourite glow-up. While their appearances within the video look like an enormous transformation for viewers, Yamada tells Dazed that it doesn’t feel that way in any case these years. “Truthfully, we now have all been friends for 15-plus years, a few of us over 20 years, so it just felt very normal. It’s so different for the viewers seeing us jump from 13-years-old to 29-years-old and seeing this huge difference,” she says.

Yamada and her friends are certainly one of many groups to post their glow-ups on TikTok. Whether it’s the shocking revelation that all of them stayed in contact, or the fuzzy feeling you get from seeing their younger selves, videos like hers have grow to be extremely popular on the platform. But why are we so fascinated with aging, especially relating to people we’ve never met?

It’s human nature to be interested by other people’s lives and to be desirous about their stories. That’s a part of the explanation why we resonate a lot with media that tells the story of growth throughout the years, like Richard Linklater’s Boyhood or the Up series which, starting in 1964, has been documenting the lives of 14 people across different social classes since they were seven years old, following them through school, relationships and careers. We naturally enjoy seeing people develop since it mirrors our own lives. “There’s a cognitive satisfaction in seeing narratives and stories unfold over time and watching personal growth provides a narrative structure that our brains find appealing,” Hendrix Hammond, psychotherapist and spokesperson for the UK Council for Psychotherapy, tells Dazed.

Hammond also finds that seeing people age over time often makes us feel empathetic towards them, as we are inclined to compare our own growth to theirs. “It’s normal for humans to be fascinated by and watch how other people grow and alter over time,” he says. “It’s because we are inclined to compare ourselves to others, so seeing another person’s growth and transformation helps us assess our own progress and life selections. It may well even be very empathetic and connecting to see another person’s journey, which may evoke feelings of compassion and understanding.”

Comparing our growth to others can actually encourage us to tackle latest challenges and experiences. “Watching other people grow stresses our must grow to be the very best version of ourselves. Thus, we’d use other peoples’ growth as points of reference for our own lives,” says Chantal Gautier, psychologist and lecturer on the University of Westminster. She also notes that observing others’ growth can actually stimulate our brain’s plasticity, or the flexibility for our brain to adapt and develop.

It’s a primal instinct for humans to note changes in the environment. Relating to noticing changes in others, there are a certain type of neurons in our brains, called mirror neurons, that allow us to empathise with others. “They’re the brain cells that get activated each after we act and after we observe the identical motion performed by another person. They play a key role in understanding and empathy. So, after we see another person grow, these neurons could be helping us to ‘feel’ their journey, making it more compelling and relatable,” psychology expert and life coach Bayu Prihandito tells Dazed.

Lots of varied emotions can come from watching people age, like admiration, joy, curiosity and impermanence. Nonetheless, nostalgia is one of the crucial powerful things we feel after we see people transform over time. Our younger selves often hold a robust sense of nostalgia. This could be another excuse why we enjoy watching stranger’s transformations – although we don’t know every little thing they’ve been through, we will physically see how far they’ve come.

In contrast, when ourselves previously we’re fully aware of all the emotions our younger selves experienced. “Our younger selves represent a time of potential, dreams and maybe fewer responsibilities. Comparing our current selves to that version could be a way of measuring if we’ve lived as much as our own expectations. It’s a mirrored image of our journey and the alternatives we’ve remodeled time,” Prihandito says.

Prihandito also says that youth is commonly related to beauty and potential, which is a component of the explanation why we’re so desirous about seeing people of their younger days. (Think: looking up your favorite celebrity from the 90s or adding “young” to your Google search.) The pressure to seem as youthful as possible is rampant online and contributes to our must consistently compare ourselves to past versions of ourselves.

So, whether it’s primal instinct or simply plain nostalgia, we’ll all the time have the will to look back on past versions of ourselves. And, if fascinated with a younger version of yourself makes you weak within the knees, rest assured TikTok has a complete catalogue of people that insist on sharing their glow-ups to satisfy your craving.