Many farmed animal advocates engage in diet change work — the attempt to convince individuals to adopt vegan diets as a way of preventing harm to animals used in our food systems. However, little is understood about the ways in which veganism is spread through a social network. This new study from Faunalytics attempts to shed light on social contagion, paving the way for more effective individual advocacy and further research into the social spread of veganism.

https://faunalytics.org/what-vegan-advocates-can-learn-from-the-social-spread-of-quitting-smoking/ 

Key Findings

1. Romantic partners are often the strongest social ties we have, which makes them strong candidates for influencing behavior—people are anywhere between 1.3 and 11.8 times more likely to quit smoking if their partner also quits. Applied to veg*nism, this may suggest that individuals in a romantic relationship may be more likely to go veg*n together versus individually. Nonetheless, limited research on this topic has revealed that individuals in a heterosexual relationship perceive that shifting to a plant-based diet together would upset both partners and thus be challenging, although the authors also found that perceived challenges were less apparent in couples with more flexible leadership styles and left wing political ideologies (Gregson & Piazza, 2023). Thus, some couples may be better suited for targeted diet-change interventions than other couples, but more research is needed to confirm this hypothesis. 
2. A non-smoking partner can also serve as a good role model—people are anywhere between 1.6 and 4.4 times more likely to quit smoking if their partner is a non-smoker, while those married to current smokers are the least likely to quit. Applied to veg*nism, we speculate that omnivores may be more likely to go veg*n if their partner is veg*n instead of an omnivore, a hypothesis supported by one study to date: Couples with different diets are more open to reducing their animal product consumption than couples with a similar diet (Gregson & Piazza, 2023). Nonetheless, the dynamics of animal product consumption and gender suggest that men may have a more difficult time going veg*n than women and that a partner transitioning to a plant-based diet may cause more tension in the male partner than the female partner among heterosexual couples (Gregson & Piazza, 2023). 
3. After romantic couples, friends have the strongest social influence on quitting smoking. In one social network analysis, a spouse was 67% less likely to smoke if their spouse had quit smoking, 43% for mutual friends, 34% for coworkers in small firms, and 25% for siblings. Entire clusters of smokers become non-smoking clusters over time, suggesting that one’s immediate social circle influences individual behavior, especially in adulthood. In contrast, adolescents tend to be more susceptible to start smoking if their friends are smokers than to quit smoking if their friends are non-smokers. In regards to veg*nism, veg*ns are up to six times more likely to be friends with veg*ns than omnivores (Nezlek et al.,  2020), which may suggest that veg*ns may have a limited social influence if their immediate social circle is already veg*n. 
4. Smoking is susceptible to social norms—although once widely popular, smoking rates have fallen over the past century worldwide, with  smokers becoming less popular in their social networks and shifting towards the edge of their networks over time. A study that tracked smoking habits across a 32-year period, from 1971 to 2003, found that smoker clusters eventually became nonsmokers altogether, suggesting a strong peer influence to quit smoking. For instance, the percentage of daily smokers in the U.S. dropped from 30% to 15% between the years of 1980 and 2012 (Our World In Data, 2023). Applying this to veg*nism is tricky as abstaining from animal products is still a niche lifestyle with just a minority of people identifying as vegan or vegetarian (e.g., 3% of U.S. adults: Pew Research Center, 2016). Not only that, but social pressure to eat animal products (e.g., when living and/or eating with non-veg*n friends and family) has been reported as a reason why people stop eating veg*n (Faunalytics, 2023; Rosenfeld & Tomiyama, 2019). This may suggest that the social influence of veg*nism may be limited as it’s yet not a popular behavior. 
5. A network analysis of over 50,000 social ties, including couples, friends, and coworkers, found that the social spread of smoking drops after three degrees of separation. In other words, a person’s smoking behavior appears to be influenced by their peers’ peers’ peers, but not any further. Importantly, the social spread of smoking is weaker with each degree of separation, meaning that closer connections are associated with more influence. However, we’re not confident that this would apply to the spread of veg*nism, but it’s worth further research. 

Figure 3. Peer Influence On Quitting Smoking 

Background

Anyone who has been vegan for a while has likely seen how their diet and lifestyle can influence or spread to those around them. Yet if each vegan was able to create two new vegans, we would have likely seen more significant shifts in the rates of veganism (Our World In Data, 2022) in recent decades. This illustrates the difficulties of understanding social contagion—the process of information (including attitudes or behaviors) spreading throughout a group—especially in relation to veganism. By understanding social contagion better, advocates can improve their diet change outreach, possibly by mastering the art of “vegan contagion.”

One way to understand social contagion is through a social network analysis where social interactions or relationships between individuals or groups of people (e.g., countries, political parties, sport teams, etc.) are mapped out and analysed. A full network, for example, is one that outlines all social ties within a particular context, such as all students within a university. But social networks have smaller networks within them of varying strengths too, such as a romantic couple within a friend group within an acquaintance group, overlapping within a classroom and the larger university group (see figure below). 

Spreading veganism or vegetarianism (combined, veg*nism)—with the long-lasting behavioral changes and beliefs it entails—requires complex contagion, which is repeated exposures by strong ties (e.g., friends and family), not just the simple spread of information (Centola, 2021). For the purpose of this review, we refer to veg*nism as a behavior (i.e., eating a plant-based diet). 

Figure 1. Social Network Example

One theory, the independent cascade model, posits that change within a social network occurs at the micro-level, like between two peers, and then cascades or spreads further within the network (Hodas & Lermanm, 2014). But as mentioned above, change isn’t always that simple, and can depend upon other factors like the number of exposures to a new phenomenon and the type of relationship between the recipient and the actor. For instance, one very influential person might have the power to influence all ten of their peers, which may be more cost-effective than trying to influence ten random, less influential individuals. In other words, it may be more effective to influence people who are connected to multiple people as they act as “gatekeepers” of information and could help spread information. 

The spread of veg*nism hasn’t been formally studied as of yet, but this study reflects on a similar behavior change that has been commonly studied: quitting smoking.  

Why Smoking Cessation?

Quitting smoking is a good parallel to going veg*n in several ways: it’s a complex behavioral change, it’s good for one’s health (Oussalah et al., 2020) which motivates people to make the change (Faunalytics, 2021), and it’s a frequently-cued behavior. For instance, cravings (for food or nicotine), a particular time of day, or a particular environment can all remind a person of the behavior they’re trying to change. All of the cues associated with these complex behaviors make them challenging to change, and make the social environment incredibly important. For example, a smoker trying to quit may find it challenging to overcome the urge to smoke at a stressful time—imagine how much harder that is if their best friend goes out for a cigarette right then or leaves their cigarettes lying around in sight. It can be similar to going veg*n: A partner eating meat in front of you or having animal products in the house provides constant cues of the behavior you’re trying to leave behind. Some people are able to “flip the switch” and quit smoking or go veg*n overnight, but for many others there’s a period of reduction or setbacks (Faunalytics, 2021). 

While smoking and animal product consumption are not perfect analogies (see the Conclusions section for more detail), the decreasing popularity of smoking may prove worthwhile for advocates to study as a template for animal product reduction. Indeed, smoking used to be widely popular, but smoking rates have fallen over the past century worldwide (Our World In Data, 2023), partly due to a combination of changing smoking norms and rising evidence of its health and environmental consequences (National Center for Chronic Disease Prevention and Health Promotion (US) Office on Smoking and Health, 2014). 

Figure 2. Quitting Smoking & Quitting Animal Products

With this literature review, we examined peer influences on quitting smoking with the goal of generating hypotheses about peer-to-peer influence on veg*nism. This was an atypical review as our goal was to carefully think about what the findings for quitting smoking in a social context may suggest for going veg*n. Please note that these studies are correlational, so they can’t tell us whether someone’s behavior causes another person to change their own behavior, it can only tell us that peer behaviors are related. We believe these findings will be beneficial for both advocates working on diet change or animal product reduction as well as researchers looking to study the social contagion of veg*nism. 

Research Team

Dr. Jo Anderson (Faunalytics) stewarded this project at the start and Dr. Andrea Polanco (Faunalytics) took over the data interpretation and writing afterwards. Jared Winslow led the preregistration phase, Abby Couture contributed to the review phases, and Dung Nguyen led the review and data extraction phases.

Conclusions

Strong Ties Predict Strong Influence 

Based on our literature review, couples who quit smoking together have the highest chances of success, followed by ‘mismatched’ couples (where a non-smoker partner serves as a role model for the smoker partner) and other peer influences like friends and colleagues. What these all have in common is that they’re considered ‘strong ties’—people you interact with regularly and/or have a meaningful connection with. 

We therefore hypothesize that omnivore couples would have the highest likelihood of adopting a veg*n diet if they both transition together (similar to couples who quit smoking together), followed by ‘mismatched’ couples where a veg*n partner serves as a role model for the omnivore partner. Nonetheless, there is some research that may suggest that omnivore couples will have more difficulty transitioning together compared to couples who share a different diet (Gregson & Piazza, 2023), but more research is needed to test this hypothesis as that study only asked participants about intentions to one’s change diet rather than measuring diet per se. 

For couples where only one of the partners is veg*n, we hypothesize a role-model effect similar to smoking. However, we acknowledge that the veg*n partner who is serving as a role model may lapse and consume animal products as this has been reported by both former (Faunalytics, 2023) and current veg*ns (Rosenfeld & Tomiyama, 2019). Thus, for animal advocacy strategies, there may be untapped potential for interventions to target omnivore couples and encourage them to transition to a plant-based diet together, which may avoid the pitfalls of just targeting one of the partners. However, we reiterate that this is just a hypothesis and that research is needed to compare a diet-change intervention between omnivore couples versus mismatched couples that share a different diet. 

Outside of couples, one study revealed that other forms of peer influences are less influential than couples’ (Christakis & Fowler, 2008). However these are still worth considering for animal advocacy as the same study noted how smoker clusters eventually became non-smoking clusters over time. Indeed, this study was also the only one to measure the spread of smoking and it found third-order effects, meaning that a smoker/non-smoker can influence not only their peers, but their peers’ peers as well. We therefore hypothesize that a veg*n’s reach will plateau after three degrees too and that at minimum, we should expect second order effects, supported by some self-reported data. In our previous study, 40% of participants remembered a family member, friend, or colleague who talked to them about meat reduction or farmed animal suffering and said that this exposure reduced their animal product consumption (Faunalytics, 2022). 

However, because veg*ns are more likely to be friends with other veg*ns (Nezlek et al,  2020), it may be unrealistic to expect entire omnivore clusters to become veg*n clusters over time, especially if there is no veg*n in that cluster to spark an influence. Even if there is a veg*n in a group of non-veg*ns, we know that veg*n stigma is an observed phenomenon (Markowski & Roxburgh, 2019) which could result in negative social interactions and perhaps a loss of friendships. A proper social network analysis that explores veg*nism can help test these hypotheses. 

Harness The Power Of Weaker Ties

Although complex behavior change is more influenced by close-knit connections like friends and family than non-friends and family (called “weak ties”), such weaker ties are still important to consider as they’re more helpful for driving product sales than stronger ties, for example (Godes & Mayzlin, 2009). This is because people receive new information that they otherwise wouldn’t have received from their immediate social circle. 

For animal advocacy, this might mean simple messages spread best (e.g., trying a new alternative protein product or a cruelty-free make-up product), sometimes virally, through such weak ties. Indeed, spreading awareness of animal suffering and/or veg*n products, such as sharing a post on social media, can be low-hanging fruit for animal advocates. In fact, we previously found that reading social media posts and news articles that discussed animal suffering actually reduced animal product consumption in meat-avoiders (i.e., vegetarians, reducetarians, and flexitarians: Faunalytics, 2022). This goes to show that animal advocates shouldn’t ignore the power of weak ties when strategizing how to influence others. 

Keep Up The Fight To Change Social Norms 

To increase your chances to positively influence your strong and weak ties, the social norms around animal product consumption also need to be in favor of veg*nism. As discussed below, while quitting smoking is more common now than it used to be, abstaining from eating animals is not yet popular. This is where the entire animal advocacy community can work together—from targeting systems to individuals—so that eating plant-based isn’t seen as a fringe behavior, but rather as a normal, healthy, and sustainable action that people can take. Changing social norms to make veg*nism appealing involves both macro (systems) and micro (individual) advocacy. 

At the macro level, messages around veg*nism should highlight how more people are eating veg*n (called “dynamic social norms”) as this signals to people that other people are changing, which in turn, can inspire others to change due to social pressure. Aside from messaging, advocates can promote veg*nism on a large scale by changing how veg*n food is presented in grocery stores, cafeterias, and restaurants so that people are more likely to pick the plant-based option over the non-veg option (these are referred to as “plant-based nudges and defaults”). 

At the micro level, more work is needed to make a vegan lifestyle appealing and inviting. This is especially important considering how veg*n stigma may be a barrier for those interested in going veg*n, especially in a peer group of omnivores. Animal advocates can thus serve as positive role models to others (e.g., by showing how veg*nism can be accessible, normal, and fun), especially if efforts are made to expand and build bridges with different social groups.

Whether your goal is to create change at a systems- or individual-level, it’s important to note that social norms have a stronger influence when the individuals referenced in the norm are similar or relevant to the observer (Sparkman et al., 2020). Additionally, veg*n stigma may affect marginalized (e.g., BIPOC) individuals more than non-marginalized individuals, which can create additional hurdles for them to switch to a plant-based diet. For these reasons, more work is needed to make our movement more inclusive, not just regarding race/ethnicity, but also in terms of ages, genders, bodies, disabilities, and sexual orientations so that the animal protection movement reflects the diversity of the wider population. Faunalytics is currently conducting a qualitative study that further investigates BIPOC inclusivity in the U.S. farmed animal protection movement.