The power of 'like' | Science News for Students

The power of 'like'

A single 'like' can make a social-media post more popular and even affect how teens behave
Oct 17, 2017 — 7:12 am EST
hands and like icons

People who post on social media want their offerings to garner legions of likes. Most readers also tend to share those posts that have gotten a large quantify of “likes.” So very popular posts go on to become even more popular. This can greatly affect what goes viral.


This is the second of a two-part series

Like it or love it, social media is a major part of life. Teens spend more than half of their waking hours online. You use some of that time to post pictures and to create profiles on social media accounts. But most of what you do is read and respond to posts by friends and family.

Clicking on a thumbs-up or a heart icon is an easy way to stay in touch. But those “likes” can have power that goes beyond a simple connection. Some social media sites use those likes to determine how many people eventually see a post. One with many likes is more likely to be seen — and to get even more likes.

What’s more, viewing posts with a lot of likes activates the reward system in our brain. It also can lower a viewer’s self-control. And posts related to alcohol may encourage teens to drink. That means that what you like online has the power to influence not just what others like, but even what they do.

Popularity on the brain

It’s no surprise that feedback from peers affects how we behave. And not always in a good way.

For example, in one 2011 study, teens doing a driving task in a lab took more risks when their friends were around. Researchers also looked at the teens’ brains during this task. They saw activity in a part of the brain that’s involved in rewards. This area is known as the nucleus accumbens. That suggests these teens were changing their behavior to try to get social approval, explains Lauren Sherman. She's a cognitive neuroscientist at Temple University in Philadelphia, Penn. Cognitive neuroscientists are researchers who study the brain.

social media word bubbles
Joining social media can give people a sense of being in the know. But posts may exaggerate how well our friends and others are feeling, making them appear much happier than we are. And that can, inappropriately, make us feel less successful than them.

Sherman wanted to know whether teens make similar changes to their behavior when they use social media. To find out, she and her team recruited 32 teens for a study, last year. All submitted photos from their personal Instagram accounts.

The researchers mixed the teens' photos with other pictures from public Instagram accounts. Then they randomly gave half of the images many likes (between 23 and 45; most had more than 30). They gave the other half no more than 22 likes (most had fewer than 15). The participant's own pictures were evenly divided between getting many or few likes.

The researchers told the participants that about 50 other teens had already viewed and rated the photos. That let the teens know how big the audience was. It also gave them a feel for how popular the pictures were.

The researchers wanted to see how the participants’ brains were responding to the different images. To find out, they had the volunteers view the photos while they were inside a magnetic resonance imaging, or MRI, machine. It uses a strong magnet to record blood flow in the brain. When brain cells are active, they use up oxygen and nutrients. MRI scans show where blood flow has increased because of this activity. When people perform some task while in the MRI machine, this test is now known as functional MRI, or fMRI.

While the teens were in the machine, researchers asked them to either like an image or skip to the next one. Teens were much more likely to like images that seemed popular — those that had more than 23 likes, Sherman's team found. The kids tended to skip pictures with few likes. And the brain's reward pathways became especially active when the teens viewed their own photos with many likes.

Story continues below image.

social media brain responses
In a study of Instagram users, reward centers in participants' brains became more active (top row) when they viewed their own images compared to when they viewed other images (middle row). When they viewed other people’s photos of risky behavior, such as cigarette or alcohol use, brain regions involved in cognitive control became less active (bottom row).
Lauren Sherman

Likes can have a subtle but significant effect on how teens interact with friends online, these data suggest. “The little number appearing below a picture affects the way [people] perceive that picture,” Sherman reports. “It can even affect their tendency to click ‘like’ themselves.”

A like is a social cue, Sherman explains. Teens “use this cue to learn how to navigate their social world.” Positive responses to their own photos (in the form of many likes) tell teens that their friends appreciate what they’re posting. A brain responds by turning on its reward center.

But seeing someone else’s popular photo didn’t necessarily turn on that reward center. Sometimes looking at the picture instead affected behavioral attitudes. For instance, cognitive control helps people maintain self-control. It also helps them think about plans and goals. The brain region linked to cognitive control tended to become less active when looking at some photos — no matter how many likes they might have. What kinds of pictures turned off this brain control region? They were photos showing risky behaviors, such as smoking or drinking.

Viewing pictures like these could make teens let down their guard when it comes to experimenting with drugs and alcohol, Sherman worries. “Repeated exposure to risky pictures posted by peers could make teens more likely to try those behaviors.”

Small act, big impact

Teens have many social media options. But all of them offer some way to like, favorite or upvote other people's posts.
Pixelkult/Pixabay (CC0)

Clicking “like” is a simple act that can have complex results. In fact, a single like can have a big impact on a post’s popularity and reach, say Maria Glenski and Tim Weninger. These computer scientists work at the University of Notre Dame in Indiana.

Glenski and Weninger studied the social news site Reddit. Its users can respond to headlines by clicking an arrow that points up or down. An up arrow, or “upvote,” is similar to a like. The researchers created a computer program that scanned Reddit every two minutes for six months. During each scan, the program recorded the most recent post on the site. Then it randomly upvoted the post, downvoted it or did nothing. By the end of the study, the program had upvoted 30,998 posts and downvoted 30,796. It left alone another 31,225 posts.

Glenski and Weninger watched to see how popular each post was four days after their program had interacted with it. The final score they used was the number of upvotes minus the downvotes. The researchers considered posts with a score of more than 500 to be very popular.

Posts that their program had upvoted did better. These posts were eight percent more likely to have a final score of at least 1,000, compared to posts the program had ignored. And upvoted posts were almost 25 percent more likely to reach a final score of 2,000 — making them extremely popular. In contrast, posts that the program downvoted ended up with scores five percent lower, on average, than were posts that the program had ignored.

Facebook like
Clicking “like” on a post can increase the number of people who see it — and have far-reaching effects on other people's behavior.

“Early up-ratings or likes can have a large impact on the ultimate popularity of a post,” Glenski concludes. “People tend to follow the behavior of the group.” If other people have liked a post, new viewers will be more likely to like it too. And that popularity can feed on itself.

Many social media sites share more of the higher-ranked — or more popular — posts. As a result, “people are more likely to see what others have positively rated,” Glenski says. So the posts that get the most likes tend to spread even more widely.

Teens should keep in mind, Glenski cautions, that just because a post is popular doesn’t mean it is a quality post. Similarly, she adds, people should pay careful attention to what they like, share or comment on. “Your actions influence what other people see and hear in the media.”

Risky business

Popular photos might signal to teens that what’s in those photos is socially acceptable. If those images show alcohol use or other risky behaviors, this could lead teens to make bad choices. That’s what Sarah Boyle concluded from a study she ran last year.

Boyle is a psychologist at Loyola Marymount University in Los Angeles, Calif. Her team recruited first-year college students to see if — and how — social media posts might affect underage drinking. Their participants included 412 incoming students. All were under 21 (the legal drinking age).

poor choices (drinking and smoking)
First-year college students who see their peers post photos of alcohol on social media are more likely to drink by their second semester, data show.

Students completed two surveys. They took the first between September and October. This was 25 to 50 days into the first half of the school year. They filled out a survey again between February and March, well into the second half of the school year. Each survey asked how much alcohol someone drank, and how often. It also asked why that person drank and what role they felt drinking plays in the college experience.

Each survey also asked students how frequently they checked Facebook, Instagram and Snapchat. And when they did go on social media, had they seen alcohol-related posts? The researchers then compared responses from the first and second surveys.

Students who saw alcohol-related posts during the first six weeks of school were more likely to drink alcohol by the second survey, the data show. Men increased their drinking more than women did. Seeing alcohol-related posts on social media increased how much they thought other male students were drinking, Boyle says. Those posts made the young men see drinking as an important part of their college experience. “These things, in turn, led them to drink more themselves,” Boyle says.

Women saw alcohol-related posts also began to view drinking as part of the college experience. They, too, increased their drinking, just not as much as the men did. However, the posts didn’t change their idea of how often other women drank. That’s probably because male students made the most alcohol-related posts, Boyle observes.

A difference also emerged between social media sites. More posts about alcohol appeared on Instagram and Snapchat than on Facebook. Boyle suspects this is because fewer parents, professors and other older adults use Instagram and Snapchat. Instagram's filters also may allow people to glamorize photos, making alcohol more attractive, she adds. Similarly, people may post photos of alcohol to Snapchat because they know their posts will disappear.

Instagram and Snapchat filters can make their subjects seem silly, fun or happy. But that may greatly distort their normal attitudes. Indeed, few people share selfies showing themselves depressed or hung over.
Jessica B./Flickr (CC BY-NC 2.0)

The important take-home message here, Boyle says, is that what students see on social media can influence their attitudes about drinking, Boyle says. “The problem with social media is that posts can distort reality.” Social media users see only highlights from the party. These are the posts that others like. People rarely, however, post pictures of their hangovers, poor grades or drinking-related injuries and accidents, she notes.

Neuroscientist Sherman hopes that all tech users will become thoughtful about their use of social media. Our online experiences are shaped by others' opinions. Going along with the crowd isn’t necessarily bad, she says. But teens need “to be aware that peer influence is a constant factor whenever they use social media.”

Glenski, the computer scientist, agrees. Social media “shapes how we perceive the world around us,” she says. Your online ratings have a big influence on what others see and hear. So it’s important that you read carefully. Think about what you like and upvote, she says. And keep in mind that “Your digital votes matter.”

Check out part 1: Social media: What’s not to like?

Power Words

(more about Power Words)

behavior     The way something, often a person or other organism, acts towards others, or conducts itself.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

cognitive     A term that relates to mental activities, such as thinking, learning, remembering and solving puzzles.

computer program     A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.

control     A part of an experiment where there is no change from normal conditions. The control is essential to scientific experiments. It shows that any new effect is likely due only to the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of it to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that gives scientists something against which they can compare their experimental data.

digital     (in computer science and engineering)  An adjective indicating that something has been developed numerically on a computer or on some other electronic device, based on a binary system (where all numbers are displayed using a series of only zeros and ones).

distort     (n. distortion) To change the shape or image of something in a way that makes it hard to recognize, or to change the perception or characterization of something (as to mislead).

factor     Something that plays a role in a particular condition or event; a contributor.

feedback     A process or combination of processes that propel or exaggerate a change in some direction. For instance, as the cover of Arctic ice disappears with global warming, less of the sun’s warming energy will be reflected back into space. This will serve to increase the rate of Earth’s warming. That warming might trigger some feedback (like sea-ice melting) that fosters additional warming.

filter     (in chemistry and environmental science) A device or system that allows some materials to pass through but not others, based on their size or some other feature. (in physics) A screen, plate or layer of a substance that absorbs light or other radiation or selectively prevents the transmission of some of its components.

icon     (adj. iconic) Something that represents another thing, often as an ideal version of it.

magnetic resonance     The vibration of two magnetic waves in synchrony, allowing one of them to strengthen.

functional magnetic resonance imaging (fMRI)    A special type of medical scanning technology for studying brain activity. It uses a strong magnetic field to monitor blood flow in the brain as an individual is performing some task (from reading or viewing pictures to thinking about various spoken words). Tracking areas of elevated blood flow can tell researchers which brain regions are especially active during those activities.

media     (in the social sciences) A term for the ways information is delivered and shared within a society. It encompasses not only the traditional media — newspapers, magazines, radio and television — but also Internet- and smartphone-based outlets, such as blogs, Twitter, Facebook and more. The newer, digital media are sometimes referred to as social media. The singular form of this term is medium.

navigate     To find one’s way through a landscape using visual cues, sensory information (like scents), magnetic information (like an internal compass) or other techniques.

neuroscientist     Someone who studies the structure or function of the brain and other parts of the nervous system.

nucleus accumbens     An area deep within the front part of the brain that is linked to pleasure and motivation.

nutrient     A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

online     (n.) On the internet. (adj.) A term for what can be found or accessed on the internet.

oxygen     A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).

peer     (noun) Someone who is an equal, based on age, education, status, training or some other features.

psychologist     A scientist or mental-health professional who studies the human mind, especially in relation to actions and behaviors. 

reward system     (Also reward center) A region of the brain that processes the pleasant reactions we get when we get smiles, gifts, pleasurable stimuli (including food) or compliments.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

social media     Internet-based media, such as Facebook, Twitter and Tumblr, that allow people to connect with each other (often anonymously) and to share information.

subtle     Some feature that may be important, but can be hard to see or describe. For instance, the first cellular changes that signal the start of a cancer may be visible but subtle — small and hard to distinguish from nearby healthy tissues.

survey     (v.) To ask questions that glean data on the opinions, practices (such as dining or sleeping habits), knowledge or skills of a broad range of people. Researchers select the number and types of people questioned in hopes that the answers these individuals give will be representative of others who are their age, belong to the same ethnic group or live in the same region. (n.) The list of questions that will be offered to glean those data.


Journal: M. Glenski & T. Weninger. “Rating effects on social news posts and comments.” Transactions on Intelligent Systems and Technology. Vol. 8, September 2017, article 78. doi: 10.1145/2963104.

Journal: L.E. Sherman et al. “The power of the like in adolescence: Effects of peer influence on neural and behavioral responses to social media.” Psychological Science. Vol. 27, July 2016, p. 1027. doi:10.1177/0956797616645673.

Journal: S.C. Boyle et al. “Different digital paths to the keg? How exposure to peers’ alcohol-related social media content influences drinking among male and female first-year college students.” Addictive Behaviors. Vol. 57, June 2016, p. 21. doi:10.1016/j.addbeh.2016.01.011.

Journal: J. Chein et al. “Peers increase adolescent risk taking by enhancing activity in the brain’s reward circuitry.” Developmental Science. Vol. 14, March 2011, p. F1.  doi: 10.1111/j.1467-7687.2010.01035.x.