Science of fitting in: Do best friends or popular peers shape teen behavior?

Study first to directly compare impact of best friends vs. classroom norms driven by popular classmates

Florida Atlantic University

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Best friends primarily shape a child’s internal emotional state and academic behavior, popular peers set the standard for public image and social media engagement.

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Credit: Alex Dolce, Florida Atlantic University

As children enter adolescence, peers become a dominant force in their lives. With adult supervision waning, teens look to agemates for guidance on how to act, think and fit in. But who matters most –friends or the popular classmates? A groundbreaking longitudinal study from Florida Atlantic University reveals that peer influence is not a monolithic process. Instead, different types of peers exert influence over entirely different domains of a child’s life.

Researchers at FAU and collaborators at Mykolas Romeris University (Lithuania) conducted a long-term study to directly compare these two sources of influence. The study, published in the journal Development and Psychopathology, is the first to simultaneously compare the relative impact of best friends versus classroom norms, which are driven by popular classmates. The findings indicate that while best friends primarily shape a child’s internal emotional state and academic behavior, popular peers set the standard for public image and social media engagement.

The investigators followed 543 students ages 10 to 14 (middle school in Lithuania is fifth through eighth grade) across a semester, examining self-reports of academic performance, emotional well-being, problem behaviors, social media use and concerns about weight. Participants also identified their best friends and classmates they considered popular. Popularity norms described classmate behaviors in each domain, weighted by popularity scores.  

“This is the first study to put best friends and popular peers in the same model and ask, ‘Who matters more, and for what?,’” said Brett Laursen, Ph.D., a professor of psychology in FAU’s Charles E. Schmidt College of Science.

The findings revealed a striking pattern. Best friends primarily shaped a child’s internal emotional states and academic behaviors, whereas popular peers set the standard for public image. Specifically, best friends were the primary influencers for behaviors reflecting internal dysfunction and maladjustment, including emotional problems, lack of emotional clarity, problem behaviors, and low school achievement. Popular peers, by contrast, shape behaviors performed in view of others. Teens emulate high-status classmates in terms of social media use and weight concerns.

“Peer influence is too often treated as a broad, undifferentiated force, but our findings show it is actually highly specialized. Adolescents are discerning; they look to their inner circle for emotional support and to the influencers and class leaders for social cues on how to present themselves to the world,” said Mary Page Leggett-James, Ph.D., lead author and associate researcher at Gallup, describing results from her doctoral dissertation at FAU. “Put differently, in the social economy of a middle schooler, best friends deal in the ‘private currency’ of emotions and adjustment, while popular peers control the ‘public market’ of social media and appearance.”

The study suggests that adolescents use different mental calculations to navigate their social world. Friendships are based on reciprocity and intimacy, which promote shared experiences and emotional states. In contrast, peer groups are organized hierarchically. Conformity through public-facing behaviors like social media use and body image are important to maintaining status in the group. Thus, youth are not just blindly following others, they are using social strategies tailored to specific social settings.

“Friendships are powerful because they are private and emotionally intense,” Laursen said. “Teens confide in their best friends. That closeness can provide support, but it can also amplify struggles. Anxiety, disengagement from school, or acting out can spread between friends and have a snowball effect. Appearance and online behavior play out on a public stage. Popular students set the standard. Others follow because that is what earns approval in the wider peer group.”

The research offers vital insights for intervention. Because different peers shape different forms of maladjustment, uniform solutions may fail.

“Peer influence is powerful, but it is not one-size-fits-all,” said Leggett-James. “Too often we treat peer pressure as if it comes from one place. But the source of influence matters. If we target the wrong peer dynamic, we risk missing the problem entirely. To reduce emotional distress or academic problems, we need to focus on friendship dynamics and help adolescents build positive peer connections – not try to ban or break up friendships. At the same time, issues tied to social media and body image require shifting status norms. When popular students display healthier, more realistic standards, they can redefine what classmates consider normal.”

Co-authors are René Veenstra, Ph.D., professor of sociology at the University of Groningen, Netherlands; and Goda Kaniušonytė, Ph.D., professor at the Institute of Psychology, Mykolas Romeris University.

The research was supported by the European Social Fund under a grant agreement with the Research Council of Lithuania, and the state budget-funded project Establishment of Centers of Excellence at Mykolas Romeris University, implemented under the Centers of Excellence Initiative of the Ministry of Education, Science and Sports of the Republic of Lithuania.

- FAU -

About Florida Atlantic University:

Florida Atlantic University serves more than 32,000 undergraduate and graduate students across six campuses along Florida’s Southeast coast. Recognized as one of only 13 institutions nationwide to achieve three Carnegie Foundation designations  -- R1: Very High Research Spending and Doctorate Production,” “Opportunity College and University,” and Carnegie Community Engagement Classification - FAU stands at the intersection of academic excellence and social mobility. Ranked among the Top 100 Public Universities by U.S. News & World Report, FAU is also nationally recognized as a Top 25 Best-In-Class College and cited by Washington Monthly as “one of the country’s most effective engines of upward mobility.” To learn more, visit www.fau.edu.

 

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Journal

Development and Psychopathology

DOI

10.1017/S0954579426101138 

Method of Research

Meta-analysis

Subject of Research

People

Article Title

Different peers influence different behaviors: Conformity to best friends and status-based norms across the transition into adolescence

Within-person association between daily screen use and sleep in youth

JAMA Pediatrics

About The Study: 

Per the results of this systematic review and meta-analysis, daily screen time has a small but significant within-person correlation with later sleep onset; however, short-term daily fluctuations in screen time appear to have minimal impact on sleep duration, efficiency, or quality. Screen time may delay bedtime but is not inherently detrimental to other aspects of sleep health in youth, contrasting with between-person studies showing stronger adverse associations. 

Corresponding Author: To contact the corresponding author, Matthew Bourke, PhD, email matthew.bourke1@deakin.edu.au.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jamapediatrics.2025.6490)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

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Journal

JAMA Pediatrics

Insufficient sleep among US adolescents across behavioral risk groups

JAMA Network

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About The Study:

 The findings of this study show a broad increase in insufficient sleep across all demographic groups, driven largely by increasing reports of very short sleep (5 hours or less). Notably, insufficient sleep increased as much or more among students without behavioral risks, suggesting that structural and environmental factors affecting most adolescents, rather than specific behaviors such as electronic media use, substance use, or sedentary activity, are contributing to wide spread sleep loss. These trends highlight the need for population-level rather than targeted interventions.

Corresponding Author: To contact the corresponding author, Greg Rhee, PhD, email tgrhee.research@gmail.com.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jama.2026.1417)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

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Journal

JAMA

 

A new theory of brain development

Cold Spring Harbor Laboratory

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Neuroscientists tracked gene expression patterns across thousands of genes in two bordering regions of the zebrafish brain, colored red and blue. “Unlike an army, which has explicit chains of command with a general at the top, development lacks a central organizer,” they write. “There is no general. Early in development, cells form a tightly coupled unit through local signals. As tissue grows and cells drift out of range, these local units fracture into subunits that inherit the states of their progenitors.”

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Credit: Zador lab/CSHL

Your brain begins as a single cell. When all is said and done, it will house an incredibly complex and powerful network of some 170 billion cells. How does it organize itself along the way? Cold Spring Harbor Laboratory neuroscientists have come up with a surprisingly simple answer that could have far-reaching implications for biology and artificial intelligence. 

Stan Kerstjens, a postdoc in Professor Anthony Zador’s lab, frames the question in terms of positional information. “The only thing a cell ‘sees’ is itself and its neighbors,” he explains. “But its fate depends on where it sits. A cell in the wrong place becomes the wrong thing, and the brain doesn’t develop right. So, every cell must solve two questions: Where am I? And who do I need to become?” 

In a study published in Neuron, Kerstjens, Zador, and colleagues at Harvard University and ETH Zürich put forward a new theory for how the brain organizes itself during development.  

For a long time, researchers thought that cells exchanged positional information mainly through chemical signaling. This works well when dealing with just a few cells, Kerstjens explains. But the brain isn’t a few cells. It’s billions of neurons, each needing to land in exactly the right place. Chemical signals can only travel so far before fading. So, how do cells deep in a growing brain automatically ‘know’ where they are? 

The answer, Kerstjens proposes, hits close to home. “Consider how human populations spread across a country over generations,” he says. “Descendants settle near their parents, so people who share ancestry end up in neighboring regions, producing large-scale geographic structures without long-range communication. We argue that a similar principle operates in the developing brain. Cells that descend from the same progenitor tend to remain near one another.” 

To test this theory, Kerstjens and colleagues built what they call a “lineage-based model of scalable positional information.” They started with theoretical computations. Then they tested their hypothesis at scale by looking at individual and group gene expression in developing mouse brains. Finally, they confirmed their results in zebrafish, showing that the model can be used across brains of different sizes. 

Kerstjens says the model supports the notion that chemical signaling works in conjunction with a lineage-based mechanism to convey positional information. And while his work focuses on the brain, the theory could apply to many other types of developing tissue, including tumors. There may even be implications for self-replicating AI models that pass information from one generation to the next, just as our own brain cells do. 

Perhaps most importantly, showing how a single cell grows into a complex organ could help scientists solve fundamental mysteries of the mind. “The brain somehow makes us intelligent,” Kerstjens says. “How did it manage to accumulate this capability, not just over its developmental time, but over evolutionary time? This is one piece in that big puzzle.” 

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Journal

Neuron

DOI

10.1016/j.neuron.2025.12.043 

Article Title

A lineage-based model of scalable positional information in vertebrate brain development

Article Publication Date

2-Mar-2026

Trends in poverty and birth outcomes in the US

JAMA Pediatrics

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About The Study: 

This study found stark disparities in birth outcomes by poverty status, with inequities growing for low birth weight in recent years. These disparities point to the need for more support during pregnancy and birth for low-income families. Antipoverty policies can provide needed resources to promote better maternal and child health, although the availability and generosity of these programs vary across states. 

Corresponding Author: To contact the corresponding author, Emily C. Dore, PhD, MPH, MSW, email edore@hsph.harvard.edu.

To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/

(doi:10.1001/jamapediatrics.2026.0004)

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

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JAMA Pediatrics

 

Science reveals why you can’t resist a snack – even when you’re full

University of East Anglia

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Research from the University of East Anglia (UEA) may finally explain why we still reach for the biscuit tin, even when we’re full.

A new study reveals that the human brain continues to respond to tempting food cues even after we’ve eaten enough.

In a world of endless adverts and snack cues on every corner, the team say their findings shed light on why so many of us struggle to maintain a healthy weight.

Lead researcher Dr Thomas Sambrook, from UEA’s School of Psychology, said: “Obesity has become a major worldwide health crisis. But rising obesity isn’t simply about willpower - it’s a sign that our food-rich environments and learned responses to mouth-watering cues are overpowering the body’s natural appetite controls.

“We wanted to better understand how our brains react to food cues when we are already feeling full.

“We studied people’s brainwaves after eating and found that even though their stomachs might be satisfied, their brains didn’t seem to care.

“In fact, no amount of fullness could switch off the brain's response to delicious looking food. This suggests that food cues may trigger overeating in the absence of hunger.”

How the research happened

In the study, 76 volunteers were monitored using Electroencephalogram (EEG) brain scans as they played a reward‑based learning game with food such as sweets, chocolate, crisps and popcorn.

Halfway through the task, participants were given a meal of one of the foods until they didn’t want another bite.

According to the researchers, the participants really were full - they reported dramatically reduced desire for the food, and their behaviour showed they no longer valued it.

But their brains told a different story.

Electrical activity in areas associated with reward continued responding just as strongly to images of the now‑unwanted food even after participants were completely full.

Dr Sambrook said: “What we saw is that the brain simply refuses to downgrade how rewarding a food looks, no matter how full you are.

“Even when people know they don’t want the food, even when their behaviour shows they’ve stopped valuing the food – their brains continue to fire “reward!” signals the moment the food appears.

“It’s a recipe for overeating.”

A habit you didn’t know you had

The findings suggest that our responses to food cues may work like habits - automatic, learned reactions forged over years of pairing certain foods with pleasure.

Dr Sambrook said: “These habitual brain responses may operate independently of our conscious decisions. So, while you might think you’re eating because you’re hungry, your brain may simply be following a well‑worn script.”

The study found no link between people’s ability to make goal‑directed decisions and their brain’s resistance to food devaluation. That means even people with excellent self‑control can be undermined by automatic neural responses.

“If you’re struggling with late‑night snacking or can’t say no to treats even when you’re full, the problem may not be your discipline - it may be your brain's built‑in wiring,” said Dr Sambrook.

“It’s really no wonder that resisting a doughnut can feel impossible,” he added.

This research was led by UEA in collaboration with the University of Plymouth.

‘Devaluation insensitivity of event related potentials associated with food cues’ is published in the journal Appetite.

ENDS
 

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Journal

Appetite

Method of Research

Experimental study

Subject of Research

People

Article Title

Devaluation insensitivity of event related potentials associated with food cues

Article Publication Date

1-Mar-2026