It’s Friday morning, and you’re having a great start to the day. Sitting at your desk at work, your regular morning coffee has kicked in, you’re well ahead on your to-do list, and you’re starting to think ahead to the exciting weekend plans you have with friends and family. 

Just then, your office bestie walks in, visibly deflated and in a bad mood. They slump into their chairs, sigh very loudly, and mutter under their breath something about canceled trains and how everything in their project is a mess. They don’t say much, but the air shifts and the positive energy in the room evaporates. You soon notice your shoulders tensing and your positive thoughts disappearing. You’re not upset as such, but suddenly you’re not all that upbeat either. Your colleague’s mood, without a word directed at you, has bled into yours. 

This is an example of emotional contagion: the “transfer” of emotion from one person to another, leading individuals to experience the same feelings as those around them without their awareness. While we’re not directly receiving the emotion, we’re automatically mimicking and synchronizing our facial expressions, vocalizations, postures, and movements with those of the other person and, consequently, converging emotionally.⁵

Emotional contagion is a form of social contagion, a phenomenon that involves the spontaneous spread of behaviors, emotions, or conditions through a group or network of people. We experience emotional contagion every day of our lives. It could be smiling when we see a toddler playing and laughing carelessly, feeling excited as a crowd cheers at a sports match, or suddenly starting to cry while watching a movie character break down with sadness. Emotional contagion can occur between two individuals, or in large groups—in fact, social contagion (and more specifically, emotional contagion) is a key component in mass hysteria events.² 

According to organizational behaviorists Sigal Barsade, Constantinos Coutifaris, and Julianna Pillemer, emotional contagion can be understood as involving four key components:

1. It includes both specific emotional reactions and broader mood states.
2. It operates through both unconscious and deliberate mechanisms, with individuals acting as both sources and recipients.
3. It can emerge in interactions ranging from one-on-one encounters to group settings, organizations, or even society-wide, potentially triggered by multiple people. 
4. It functions as a form of social influence that shapes not only emotional responses but also subsequent thoughts and behaviors.

In terms of what causes emotional contagion, research suggests that three core mechanisms are responsible:⁵

1. Mimicry: People unconsciously and automatically mimic the facial expressions, vocalizations, postures, and movements of others during interactions. This imitation is rapid, subtle, and often not consciously noticed. For example, if you’re sitting with another person and they are resting their head on their hand, you might find yourself in the same position as well. 
2. Feedback: Once mimicry occurs, the feedback from our own facial expressions, posture, and tone of voice actually influences our own emotional experience. This is based on the idea that expressing an emotion physically can intensify or generate that emotion internally. For instance, furrowing your brow might increase feelings of frustration or sadness.
3. Contagion: As a result of mimicry and feedback, we begin to “catch” the emotions of those around us. The emotional state of one person can therefore trigger a similar emotional state in another, even without words. This contagion effect is supported by neurological findings, including the role of mirror neurons, which fire both when we perform an action and when we observe someone else performing the same action.⁷

Emotions: Automatic, physical responses that arise unconsciously in reaction to internal or external stimuli. They contrast with feelings, which are the conscious awareness and interpretation of those emotional responses, shaped by individual perception, thought, and context.

Social contagion: The spread of behaviors, emotions, or ideas through a group or society, often unconsciously, as people mimic or are influenced by those around them.

Mimicry: The automatic and often unconscious imitation of another person’s expressions, gestures, speech, or behavior, usually as a way to build a connection or respond to social cues.

Palekh box: A small, hand-painted lacquer box originating from the village of Palekh in Russia. This item was the central focus of a famous experiment on social contagion. 

Mass hysteria: A phenomenon where a group of people collectively experience similar physical or emotional symptoms, such as fainting, anxiety, or panic, without an identifiable physical cause. 

Mirror neurons: Specialized brain cells that activate both when you perform an action and when you observe someone else doing the same action. These neurons are thought to play a key role in imitation, empathy, and understanding people's emotions and intentions, as they allow us to "mirror" the experiences of others in our own brains.

Dual-process theories: Psychological models that explain how we think, feel, and make decisions using two distinct systems of processing: System 1 and System 2. 

In 1872, Charles Darwin suggested that the way we express emotions on our faces can influence how strongly we feel them.¹⁸ In other words, showing an emotion openly tends to make it feel more intense, while holding it back can reduce its impact. For example, someone who acts out their anger with big gestures may end up feeling even angrier, whereas someone who suppresses their fear might experience it less intensely. On the other hand, staying still and calm when feeling grief could help a person regain emotional stability faster.

However, even as early as 1759, philosophers such as Adam Smith observed that people imagine themselves in each other’s situations. In his book, The theory of moral sentiments, he wrote “though our brother is upon the rack, [...] by the imagination we place ourselves in his situation, we conceive ourselves enduring all the same torments, we enter as it were into his body, and become in some measure the same person with him, and thence form some idea of his sensations, and even feel something which, though weaker in degree, is not altogether unlike them.”¹⁶ This early insight captures the essence of emotional contagion: our ability to emotionally resonate with others simply by imagining their experience.

Another important contribution to our understanding of emotions and how they are shared with others comes from the work of American philosopher and psychologist William James. In the late 19th century, he proposed that emotions arise from physical changes in the body.¹⁹ According to this view, we don’t tremble because we’re afraid—we feel afraid because we tremble. This idea reinforced the role of physical expression in shaping emotional experience and helped pave the way for future theories of emotional contagion.

During the course of the twentieth century, our understanding of emotions and emotional contagion shifted from philosophical observations to psychological theory and measurement. In the mid-20th century, research on facial expressions by psychologists Paul Ekman and Wallace Friesen suggested that people across cultures automatically recognize and sometimes mimic each other's emotions.²⁰ This gave weight to the idea that emotional contagion could be partly hardwired, and not just socially learned.

Humans even started to look at emotional contagion in animals. Research by behavioral psychologist Robert Miller and his team during the late 1950s and early 1960s demonstrated that monkeys are capable of transmitting fear through nonverbal cues such as facial expressions, body posture, and vocalizations.²¹ These fear-related signals act as alerts to other monkeys, warning them of potential danger. Observing these cues, other monkeys appear to “catch” the fear and become more likely to engage in avoidance behaviors that help them respond to threats appropriately.

It wasn’t until 1993 that American social psychologist Elaine Hatfield, along with her colleagues John Cacioppo and Richard Rapson, formally introduced the emotional contagion hypothesis and gave it a clear scientific framework.¹⁷ Their initial theory was based on mimicry and feedback, and how these two mechanisms work together to cause emotional contagion. During the same decade, various scientists developed what’s known as the Emotional Contagion Scale, which is designed to assess people’s susceptibility to “catching” various emotions such as joy, happiness, love, fear, anxiety, anger, sadness, and depression.^5,6 The discovery of mirror neurons by Giacomo Rizzolatti, Luciano Fadiga, Leonardo Fogassi, and Vittorio Gallese in the early 1990s provided another avenue for explaining emotional contagion from a neurological perspective. Today, we know that mimicking other people is an automatic process, neurologically triggered by observing their actions.²²

In more recent decades, research on emotional contagion has been conducted in organizational and group settings, as well as within online spaces where facial expressions and visual cues are absent. So what’s next? With our increased use and reliance on chatbots and voice assistants, both at home and in public spaces, research on emotional contagion will likely shift toward human interactions with AI. In particular, an exciting frontier lies in exploring how the degree to which we anthropomorphize AI might shape the emotions we experience during our interactions with it.

Adam Smith

18th-century Scottish philosopher and economist best known for his foundational work in classical economics, particularly The Wealth of Nations. He also explored moral psychology in The Theory of Moral Sentiments, where he introduced early ideas about empathy and emotional resonance between individuals.

Charles Darwin

One of the most famous names in science, English naturalist and biologist Charles Darwin is best known for developing the theory of evolution by natural selection in the 19th century. In addition to his work on biology, he also studied human emotions and argued that emotional expressions are universal and have evolved to serve important social and survival functions.

William James

Often regarded as the father of modern psychology in the United States, philosopher and psychologist William James is best known for his influential work on consciousness, emotion, and pragmatism during the 19th century. This includes the James-Lange theory, which proposed that emotions result from bodily responses to external events.

Robert Miller 

Behavioral psychologist known for his research in the 1950s and 1960s on observational learning and emotional transmission in nonhuman primates, particularly monkeys. His work demonstrated that monkeys could “catch” fear by observing the facial expressions and behaviors of other frightened monkeys, offering early evidence for emotional contagion in animals.

Elaine Hatfield 

American social psychologist known for her pioneering research on romantic love, emotional contagion, and human attraction during the second half of the 20th century. She was one of the first to scientifically define emotional contagion and explore how people unconsciously “catch” emotions from others through facial expressions, voice, and posture.

Sigal Barsade

American organizational psychologist known for her influential research on emotional contagion, emotional intelligence, and workplace culture. Her pioneering work from the 1970s and 1980s showed how emotions—especially those expressed subtly or nonverbally—can spread through teams and organizations, shaping collaboration, morale, and performance.

Emotional contagion has profound effects not only on our own internal state but also on how we interact with other people. These impacts can be both positive and negative, depending on the emotion, the people involved, and the overall context—even whether you’re a man or a woman!¹⁵

Empathy

Psychology models posit that emotional contagion is the “root of empathy” and a crucial step in developing empathy towards other people.¹ It’s argued that primitive emotional contagion is a basic building block of human interaction, as it can help us to understand and share the feelings of others.⁴ 

Elaine Hatfield, Richard Rapson, and Yen-Chi Le describe empathy as involving three key abilities: sharing others’ feelings, understanding those feelings cognitively, and having a compassionate motivation to help. Emotional contagion, they argue, contributes primarily to the first two.⁵ Through mimicry (e.g., copying facial expressions or posture), feedback (internal emotional responses triggered by these mimicked behaviors), and ultimately contagion (actually feeling the other’s emotion), people experience a subtle, often unconscious alignment with others’ emotional states. This alignment enables a sort of “emotional resonance,” allowing one to feel into another’s experience, which is a core feature of empathy. 

Group behaviors

In group settings, emotions can be particularly “infectious.” Whether in workplaces, classrooms, or protests, emotional contagion can significantly influence how groups of individuals think, interact, and perform. Research has shown that even a single emotionally expressive group member can subtly shift the tone of an entire team, affecting not only group cohesion but also measurable outcomes like performance and satisfaction.¹⁴ This has been referred to as an emotional “Ripple Effect.” 

In a study by organizational psychologist Sigal Barsade, undergraduate business students were assigned to small groups tasked with a collaborative decision-making exercise.¹⁴ The students were unaware that each group included a trained actor (a “confederate”) who deliberately expressed a specific emotional tone. The emotion was either cheerful or irritable, high-energy or low-energy. The aim was to test whether this person’s displayed mood would spread to other group members and affect team performance.

Across all groups, participants “caught” the mood of the confederate. Those in groups with a cheerful actor felt happier, reported more cooperation, and performed better, both in their own assessment and in how they were rated by others. Conversely, groups exposed to negative emotions showed less collaboration and more conflict. 

Harmful behaviors in adverse conditions

While emotional contagion is usually quite mild and temporary, it can have more serious consequences in certain contexts and conditions. One striking example occurred at a secondary school in Mozambique’s capital, Maputo, when a wave of fainting spells and emotional outbursts spread rapidly among adolescent female pupils.

Because the school had been built over a family cemetery, these behaviors were initially believed to be caused by spirits. However, a group of researchers from Mozambique, Portugal, Brazil, and the USA explored the harmful behaviors among the school girls (fainting, verbal aggression, and threats towards staff and pupils) from the perspective of emotional contagion.⁹ The researchers asked 154 students to fill out questionnaires about their background, relationships, levels of anxiety, and personality traits to see what factors might be linked to these emotional episodes. 

The results revealed that students exhibiting emotional contagion behavior (ECB) reported significantly higher levels of anxiety, along with certain personality traits such as extroversion, neuroticism, and psychoticism. Interestingly, students with a prior history of ECB were over eight times more likely to experience it again, suggesting a pattern of vulnerability. In contrast, students in a romantic relationship were much less likely to develop ECB symptoms, suggesting that emotional support and personal connections might serve as protective factors. 

The events witnessed in Maputo provide further evidence for the high presence of emotional contagion in populations experiencing high levels of adversity (e.g., experiences of early loss, stress, or oppression), cultures with strong traditional beliefs, and people from low socio-economic levels.8 In such contexts, culturally sensitive mental health services are crucial to stop uncontrolled emotional contagion escalating into mass psychological crises. 

Emotional contagion has been at the center of research debates for decades, particularly around whether it’s an automatic response or something shaped by our social environment. Regardless of the mechanism behind the phenomenon, emotional contagion itself can lead to widespread controversies and have far-reaching consequences for communities and nations. 

Conscious or unconscious?

Most researchers view emotional contagion as an automatic, unconscious process rooted in biology. In their original hypothesis on emotional contagion, Hatfield, Cacioppo, and Rapson argued that people instinctively mimic the facial expressions, tone of voice, and posture of others, which then triggers similar emotions in themselves through internal feedback.¹⁷ 

Neuroscience research supports this idea, showing that mirror neurons may allow us to “mirror” others’ emotional states.²³ In one study, when participants observed someone else experiencing disgust (e.g., seeing a facial expression of disgust), their own anterior insula—the same brain region activated when they personally felt disgust—also lit up. This overlap in neural activation suggests that the brain uses shared circuits to represent both personal and observed emotions, providing strong evidence for the presence of mirror neurons and their role in emotional contagion.²³ 

However, studies also show that emotional contagion isn’t purely automatic, but also shaped by conscious thought and social context. From this perspective, emotional contagion works not only by mimicry, but also by individuals consciously noticing, interpreting, and comparing their emotional states to those around them. For example, Hsee, Hatfield, and Chemtob found that people often make deliberate judgments about others’ emotions and adjust their own feelings accordingly.²⁴ Hence, emotional contagion may also depend on factors like attention, empathy, and the relationship between individuals. 

Social control of emotional contagion

Building on the biological vs. social debate in emotional contagion research, psychologists Monika Wróbel and Kamil Imbir further challenged the entirely reflexive model. They argue that emotional contagion is often influenced by social context and top-down cognitive processes.²⁵ For example, people don’t automatically mimic or share the emotions of someone they dislike, even if the person is smiling or laughing. This suggests a more selective, flexible mechanism behind emotional contagion.

Wróbel and Imbir instead propose the “Correction Hypothesis,” which suggests that when people encounter an emotional expression, they initially respond with a default reaction (like smiling back at a happy face). But this response can be adjusted—or “corrected”—based on social goals, group dynamics, or contextual understanding. For example, you may pass a coworker in the hallway who is smiling, so you smile back automatically. But then remember you’re in the middle of a conflict with them, so you quickly neutralize your expression. Drawing from dual-process theories, the authors argue that this correction can occur both consciously (when we deliberately assess a situation) and unconsciously (as an automatic adjustment based on past experience or social cues). This nuanced model helps explain why emotional contagion doesn't always happen and why we might sometimes react with the opposite emotion, depending on who the sender is or what we perceive their intentions to be. 

More recent research supports the social context model, suggesting that emotional contagion may decrease as we become more acquainted with another person. A longitudinal study by researchers tracking unacquainted pairs over six weekly Zoom conversations found that, as interpersonal closeness grew, emotional contagion actually declined.²⁶ This suggests that as people become more comfortable with each other, they may feel less need to automatically mirror one another’s emotions, allowing for greater emotional independence and divergence.

Geopolitics

Emotional contagion can have serious effects on global politics, especially in places like China. When tensions rise internationally, social media can amplify emotional messages—like those about national humiliation—leading to widespread public outrage. These emotions don’t stay isolated and can quickly ripple through communities. On platforms like Sina Weibo, a popular Chinese social media platform, posts about humiliation have been linked to growing support for aggressive moves like military action or trade restrictions.²⁸

Political scientist Michael Masterson warns that this emotional wave becomes especially risky during crises. Even though China’s leaders aren’t elected, they still face pressure from the public and may feel forced to act tough to avoid backlash. As outrage spreads online, it becomes harder for the government to stay in control. Narratives meant to unify the country can suddenly fuel anger and push leaders toward conflict, even when they might want to keep the peace—especially in hotspots like Taiwan or the South China Sea.

Effects on consumer behavior

The decisions we make around what to buy are highly social. Whether it’s the sense of connection we have with the celebrity endorsing a new product in an advert, or the conversation we have with the friendly store assistant who helps us decide on the best appliance for our needs, we never make product choices in isolation. 

Within this context, research has shown that emotional contagion can shape consumer attitudes toward products. In a pair of experiments, marketing professors Daniel Howard and Charles Gengler explored how the emotions of one person can influence the opinions of another person toward an item.¹⁰ 

When the study participants signed up for the study, they were told its purpose was to explore the feasibility of marketing lacquered Russian palekh boxes in the United States. While these ornaments are popular and well-known in their homeland, they are not widely sold elsewhere. Participants received a booklet featuring information about sample palekh boxes, along with an article about their history and craftsmanship, and were asked to review these before evaluating one box. As an incentive, they were entered into a prize draw to win one of the highly valued boxes. When they pre-tested participants’ perceptions of the boxes, they found that they were perceived as highly valuable and desirable. 

In the first experiment, pairs of adult women who didn’t know each other were assigned roles as either a “sender” or a “receiver.” The sender’s mood was manipulated by making her believe she had either won a palekh box (to induce happiness) or nothing (neutral mood). Some receivers were also led to believe the sender had shared a prize with them—such as giving them a six-pack of Coca-Cola—to create a sense of liking. The pair then sat together to evaluate the palekh box while being silently observed and videotaped to measure smiling. Afterward, both participants rated their mood and how much they liked the product through questionnaires. 

The second experiment tested whether actually seeing the sender’s face was necessary for emotional contagion to occur. In this version, all senders were happy, but in some cases, a screen blocked their facial expressions. 

The findings of the first study showed that when the “receiver” interacted with the “sender,” who was visibly happy and whom they liked, the receiver not only mimicked the sender’s smiling but also reported feeling happier. This observation clearly showed emotional contagion. This shared happiness led the receiver to view the product more positively. Notably, the sender’s cheerful mood also affected the receiver’s opinion of the product, even though the sender didn’t say anything positive about it.

In the second iteration, when receivers couldn’t see the sender’s face, they smiled less, felt less happy, and gave less favorable product ratings. This finding suggests that facial or behavioral mimicry contributes to how emotional contagion works. However, as the next case study shows, we now know that facial mimicry is not always a requisite for emotional contagion. 

So next time you’re watching an overly enthusiastic influencer celebrating the benefits of a new product on Instagram, have a think about whether your opinion is shaped by the item itself or the massive grin across their face. 

Facebook contagion

Emotional contagion doesn’t just occur in face-to-face interactions. While we often associate the phenomenon with someone else’s smile, tone of voice, or body language, research shows that emotions can spread through the content we see online.

In a groundbreaking and controversial 2014 study, communications and data specialists Adam Kramer, Jamie Guillory, and Jeffrey Hancock tested whether emotional contagion could occur on a massive scale online without any physical or verbal interaction.¹¹ Nearly 690,000 users unknowingly took part in the experiment where Facebook’s algorithm reduced either the number of positive or negative posts they saw on their News Feed for one week. Two parallel experiments were conducted: one reduced exposure to positive emotional content from friends in the News Feed, while the other reduced exposure to negative emotional content in the News Feed (all posts). Posts were considered positive or negative if they contained at least one positive or negative word. 

The findings of the study provided strong evidence that emotions can be contagious through digital text alone, without the need for direct interaction or nonverbal cues. People exposed to fewer positive posts wrote more negative updates themselves, while those who saw less negativity became more positive in their own posts. Emotional tone was measured using linguistic analysis software that tracked the frequency of positive or negative words. Although the individual effects were small, the sheer scale of the network meant the emotional impact reached millions. 

The study, however, sparked considerable controversy. The Facebook users involved in the study were not explicitly told they were participating in a psychological experiment. That is, they had their News Feeds deliberately altered without their knowledge, raising questions about transparency and autonomy. While Facebook’s terms of service included broad consent for data use, some argued this did not constitute clear or informed consent from a research ethics perspective.¹² 

And then there’s the possible harm that can be caused by attempting to manipulate the emotions of users. As Kate Crawford, Senior Principal Researcher at Microsoft, pointed out, we can’t know to what extent participants were harmed psychologically (or even physically) by the negatively skewed feeds.¹³ This is particularly concerning for users with existing mental health concerns who may have struggled as a result of the experiment they were unknowingly participating in. If the study had undergone a rigorous ethical review, as is standard research practice, participants would likely have access to support services in the event that they felt negatively impacted.  

What’s remarkable about this study is that neither Facebook, a peer-reviewed journal, nor an Ivy League university foresaw the backlash that later erupted. The experiment became the focus of several papers that critically examined not only the study’s ethical failings, but also posed important questions such as: are pre-social media ethics and regulations still fit for use in today’s digital society?²⁷ 

Does emotion affect our ability to make rational decisions?

Ever wonder why it's so hard to stay logical when you're overwhelmed with emotion? In this article, Tiantian Li breaks down how emotions can subtly influence our decision-making processes. It’s a compelling look at how feelings shape choices in ways we often don’t realize.

TDL Brief: Online Toxicity

Social contagion, and more specifically emotional contagion, plays a key role in online toxicity. Rude, aggressive, and degrading attitudes and behavior exhibited on online platforms, particularly gaming platforms, quickly spread among online users. Dan Pilat and Dr. Sekoul Krastev explore emotional contagion and the other driving forces behind online toxicity and what interventions can do to stop it.

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