Friends affect how our brain responds to shopping
We like to think our shopping decisions come down to personal preference. But then a friend gives a quick nod of approval to a pair of sneakers, and suddenly the choice just feels right – almost without a second thought.
A new project led by Jia Jin at Shanghai International Studies University suggests that this social nudge reaches past surface influence and into coordinated brain activity.
The researchers tracked more than 100 undergraduates for an entire semester and logged every change in their friendship network.
In a separate experiment, the team scanned dozens of the student’s brains while they watched a series of advertisements together.
Friends shape our shopping opinions
The behavioral part of the study began with 175 students who rated everyday products on price, quality, and appeal. Agreement was strongest for practical gadgets but still showed up for status items such as branded shoes.
Over 16 weeks of campus life, the friendships ebbed and flowed, and the rating data shifted with them. Pairs who grew closer showed steadily shrinking opinion gaps, while pairs who drifted apart edged toward stranger‑level disagreement.
“Friends, compared to nonfriends, exhibit higher similarity in product evaluation,” explained Jin. By week 16, average distance within friend pairs had dropped by an extra eight percent – a subtle but reliable change that mirrored the strengthening ties.
In 2018, Carolyn Parkinson observed that neural responses when viewing audiovisual movies are exceptionally similar among friends. The new project extends that insight from entertainment to the daily act of spending money.
Shopping ads and syncing brains
The imaging portion of the study placed 47 volunteers into a 3‑tesla scanner and recorded oxygen‑related signals with fMRI while each watched sixty short commercials beside a friend.
The pair’s brain activity revealed cortical areas lighting up in near unison, almost like two stereos tuned to the same station.
The alignment, or neural synchrony, emerged most strongly in the ventromedial prefrontal cortex and the precuneus. These brain regions are known for weighing value, recalling personal associations, and judging social meaning.
When a shiny logo flashed, friends’ reward circuits rose and fell together, suggesting that the brand carried comparable weight for both people.
Friendship and shopping preferences
A follow‑up meta‑analysis linked the shared activity to object perception, visual attention, memory consolidation, and reward processing, weaving a tidy bridge from perception to choice.
Strangers placed in the same room and shown the identical ads displayed weaker, noisier patterns with no consistent overlap across those networks.
Notably, shopping-related brain synchrony shifted with self-reported closeness. Friends who rated their bond a perfect ten showed almost twice the inter-brain correlation seen in weaker pairs, hinting that emotional intimacy tunes friends’ shopping responses.
Predicting what your buddy will buy
Jin’s group next trained a ridge regression model on each volunteer’s functional connectivity map, feeding the algorithm patterns from hundreds of brain regions rather than surface‑level behavior.
The model learned to flag a yes‑or‑no intention to buy every product shown onscreen.
Accuracy reached 63 percent for predicting the participant’s own choice and 59 percent for forecasting a friend’s choice, both comfortably above the 50 percent chance line.
Because the algorithm needed only the viewer’s brain data, the result serves as a proof of concept for inferring another person’s future action from a third‑party scan.
Taking advantage of social bonds
Marketers see a goldmine in this possibility – envisioning perfectly timed, personalized ads delivered in key social moments.
Privacy advocates, on the other hand, see a Trojan horse, cautioning that neuromarketing could shift from tracking group behavior to probing individual minds.
For now, the researchers emphasize that the predictive edge applies only to close ties. The machine guessed the intentions of a randomly paired stranger no better than a coin toss, showing that the social bond is the secret sauce.
Why neural similarity matters
Social scientists label this pull homophily, the tendency to gravitate toward people who see the world as we do. The current paper suggests the arrow points both ways, because new data show we also come to see the world more similarly after the friendship forms.
A hyperscanning study last year found the opposite trend during open‑ended conversation, in which friends diverged and strangers converged as the chat unfolded.
The result hints that context decides whether shared history promotes alignment or encourages partners to seek novelty.
Shopping and friends: The feedback loop
Dartmouth researchers have shown that synchronized activity in the posterior cingulate during live storytelling predicts how accurately friends recall the plot the next day. Overlapping signals may mark moments the group deems important.
Taken together, the data portray shopping and friendship as a feedback loop: similar minds become friends, and friendship shapes those minds to stay in sync, especially in shopping choices. This shaping explains how social norms form quickly within tight circles.
Shared brain patterns help explain viral fashion crazes, speculative bubbles, and information cascades on social media.
A flashy post that resonates with one member of a tight‑knit group can ripple outward through synchronized attention and reward circuits, turning a niche trend into a crowd movement.
Broader implications of the study
Educators designing group projects might harness the same principle. Placing students with strong positive ties together could amplify engagement and recall, while carefully mixing near‑strangers might spark creative friction and prevent echo chambers.
Clinicians are exploring whether disrupted synchrony signals social difficulties in autism and schizophrenia. If so, friendship‑driven alignment could serve as a healthy benchmark, guiding therapies that aim to restore interpersonal attunement.
The present work leaves one puzzle unsolved: Does deeper neural similarity in shopping spark the friendship, or do friends shape that similarity? Only longitudinal scans that begin before two people meet can settle the debate.
The study is published in the Journal of Neuroscience.
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