Because the animals farmed for food (chickens, pigs, ruminants, fish) are most probably sentient and able to suffer (Low, 2012; Fleischman, 2020), their mass production and instrumental use for consumption poses a pressing moral problem (Singer, 1975; Francione, 2020; Bruers, 2021). At any given moment, there are billions of vertebrate animals that are being farmed for food globally and most are raised in factory farms to maximize productivity (~74% of farmed land animals and virtually all farmed fish; Anthis & Anthis, 2019). Common sources of animal suffering include: intensive confinement in artificial conditions, unhygienic overcrowding, early mother-offspring separation and mutilating procedures (e.g., debeaking of chickens, tail docking of pigs, disbudding of cattle; Graça, 2016; Nordquist et al., 2017). Even “humane” slaughter typically involves stunning by a captive bolt, through electrocution or gas suffocation (Browning and Veit, 2020). To deny sentient beings bodily autonomy and care simply because they do not belong to the human species would be arbitrary species-based discrimination (i.e., speciesism; Bruers, 2021). Boycotting products for which animals were exploited and harmed by adopting a vegan lifestyle “as far as possible and practicable” seems to be a logically consistent approach to avoid speciesism and prevent suffering (Wrenn, 2018; Francione, 2020; Bruers, 2021). Likewise, avoiding the killing (i.e., vegetarianism) and exploitation of farmed animals (i.e., veganism) for consuming their flesh and byproducts as food is often a primary motive of veg*ns (Janssen et al., 2016; Rothgerber, 2017). Although animal rights arguments arguably provide the clearest challenge against animal-product consumption, the (over)consumption of animal products also poses environmental and health problems (Clark et al., 2019; Willett et al., 2019).

Indeed, the widespread global consumption of animal products, particularly in Western countries, is a leading cause of urgent environmental problems, including the decimation of natural habitats and wildlife, nutrient pollution and global warming (Machovina et al., 2015; Springmann et al., 2016; Poore and Nemecek, 2018). While environmental impacts may vary considerably depending on the type of animal product and the producer (up to 50-fold for the same product; Poore and Nemecek, 2018), plant-based foods are generally less resource-intensive (excl. nuts, legumes) and polluting (Poore and Nemecek, 2018; Shepon et al., 2018), especially compared to red and ruminant meats (10–100 fold impact; Clark et al., 2019, 2022). Likewise, diets with less animal products (e.g., healthy meat-reduced, no ruminant meat, veg*n) offer substantial environmental benefits, with vegan diets being the most eco-friendly (Hallström et al., 2015; Chai et al., 2019). Although modern plant-based diets increasingly include highly processed animal-product alternatives (e.g., sausages, burgers), which are usually more impactful than minimally processed plant foods (MacDiarmid, 2021), actual animal products are overall still less environmentally sustainable than these alternatives (Bryant, 2022; Clark et al., 2022). Only in very rare cases a healthy diet with some meat (mainly local) is more sustainable than a veg*n diet (e.g., many processed foods from afar) (Chai et al., 2019). Directly allocating more plant crops for human consumption rather than feeding livestock would allow to reduce global food-feed competition and foster intra- and intergenerational equity while maintaining land to conserve biodiversity and regaining land to tackle climate change (Stoll-Kleemann and Schmidt, 2017; Poore and Nemecek, 2018).

Lastly, an excessive consumption of animal products that include high levels of saturated fat and cholesterol has been associated with chronic non-communicable diseases of welfare that lower life expectancies (Springmann et al., 2016; Wang et al., 2016; Clark et al., 2019; Barnard and Leroy, 2020). In particular, higher intakes of (un)processed red meat have been linked with cardiovascular disease (Wang et al., 2016), stroke (Kim et al., 2017), cancer (Wang et al., 2016), obesity (Rouhani et al., 2014) and type 2 diabetes (Neuenschwander et al., 2019). Nevertheless, the exact health effects of high meat consumption are difficult to disentangle because of potential confounding with (other) unhealthy behaviors (Boutron-Ruault et al., 2017). By contrast, fish and seafood are typically associated with improved health (Clark et al., 2019, 2022), though the (over)exploitation of wild-caught sea-animals and aquaculture expansion also poses environmental and animal welfare problems (Lam, 2019). In addition, avoiding factory farmed animal products (esp. from chickens and pigs) may decrease the risk of spreading zoonotic infectious diseases (Karesh et al., 2012; UNEP, 2020; Hayek, 2022) and antibiotic-resistance related illness (Tang et al., 2017; Hayek, 2022).

A common motive among people to adopt veg*n diets is to prevent and treat diseases of welfare (e.g., obesity, type 2 diabetes, cardiovascular disease) (Radnitz et al., 2015; Cramer et al., 2017; Costa et al., 2019) and nutritional science indicates that well-planned veg*n diets may indeed serve this function (Melina et al., 2016; Medawar et al., 2019; Selinger et al., 2022). Nevertheless, it is important to note that plant-based diets can also be unhealthy if they include unhealthy ingredients (e.g., highly processed plant-based alternatives high in fat, sugar and salt) or exclude healthy plant-based foods (e.g., vegetables, fruits, whole grains, olive oil, nuts) (Clark et al., 2019; Barnard and Leroy, 2020; MacDiarmid, 2021). There is also weak evidence that a vegan diet increases the risk of bone fractures, which could be due to lower intakes of vitamin B-12, vitamin D, calcium and protein (Craig, 2009; Selinger et al., 2022). Vegan diets thus require a reliable source of these nutrients via fortified foods or supplements (other nutrients of potential concern are omega-3-fatty acids, taurine, iron and zinc) (McCarty, 2004; Craig, 2009). Another common health motive among veg*ns is the promotion of physical and mental fitness (e.g., lose weight and gain energy) (Radnitz et al., 2015; Cramer et al., 2017; Costa et al., 2019). Evidence as to whether veg*n diets improve or decrease mental health (e.g., depression) is, however, mixed and not robust (Rosenfeld, 2018; Selinger et al., 2022).

Although veg*n diets could in principle provide integrated solutions to avoid animal, environmental and health harms associated with animal-product consumption, veg*ns remain a minority and claims against animal-based diets are often resisted by members of the omnivorous majority (Morris et al., 2014; De Groeve and Rosenfeld, 2022). This resistance has sparked a lot of academic interest (Graça et al., 2019).

Over the past decades, a vast body of literature has emerged on the barriers and enablers to eat less animal products and to adopt veg*n diets (Corrin and Papadopoulos, 2017; Graça et al., 2019; Taufik et al., 2019), with important work on the history of meat-eating (Leroy and Praet, 2015; Chiles and Fitzgerald, 2018), reviews on the psychology of veg*nism (Ruby, 2012; Rosenfeld, 2018) and systematic reviews on interventions to reduce meat eating (Bianchi, Dorsel, et al., 2018a; Bianchi, Garnett, et al., 2018b; Harguess et al., 2020; Kwasny et al., 2022). Other reviews discussed meat reduction or plant-based diets/alternatives within the context of health promotion (Corrin and Papadopoulos, 2017; Bryant, 2022), pro-environmentalism (Hartmann and Siegrist, 2017; Bryant, 2022) and animal protection (Mathur et al., 2021). In addition, various theories have been applied to examine meat-eating (Povey et al., 2001; Graça et al., 2016; Grünhage and Reuter, 2021), including cognitive dissonance theory (Festinger, 1962) to gain insight in the meat paradox (“how can people care about animals, but also eat them?”) (Loughnan et al., 2014; Lin-Schilstra and Fischer, 2020) and the psychology of meat-eating as a morally questionable and dissonance-arousing activity (Bastian and Loughnan, 2017; Rothgerber, 2020). This vast literature indicates that the promotion of meat reduction and veg*n dietary changes is held back by a complex and diverse set of barriers, involving both macro-level historical, economic, political, technological and societal barriers and micro-level psychological barriers concerning awareness and habitual behavior, conflicting goals and values, ambivalent feelings and moral disengagement (Graça, 2016; Graça et al., 2019; Harguess et al., 2020).

More in particular, vegetarian and especially vegan diets may be criticized for being a privilege that may not be achievable for everyone due to medical conditions (e.g., health disorders), increased vulnerability (e.g., childhood, pregnancy), restricted food access (e.g., food deserts, livestock dependency), a lack of nutrition literacy, time or money (Greenebaum, 2017; Leroy et al., 2020). Cooking with fresh plant foods may be time-consuming while highly processed plant-based convenience foods are less nutritious in comparison (MacDiarmid, 2021). In addition, besides veg*n dietary changes, “less but better” animal products (i.e., more healthy, eco- and animal-friendly) and production systems (e.g., agroecological, regenerative) could provide pragmatic solutions to improve the global food system and human, environmental and animal health (Sahlin and Trewern, 2022).

In response to these criticisms, one may argue that an insistence on 100% purity in vegan practice is counter-productive (cf. “as far as possible”) (Leenaert, 2017) and that the ability to make healthy food choices in general is a luxury that requires nutrition literacy (Greenebaum, 2017). In addition, Bryant’s (2022) meta-analysis indicates that plant-based convenience foods are generally more nutritious than the animal products they replace. However, nutritional profiles of plant-based alternatives are highly variable (see also Clark et al., 2022) and further improving their healthiness (e.g., reducing salt and increasing protein, iron, vitamin B-12 content), familiarity, price and sustainability is recommended. Lastly, the promotion of veg*n diets may be complemented with “less but better” strategies, although these strategies have been criticized for lacking clear implementation goals (Sahlin and Trewern, 2022), while veg*n diets provide clear goals that also challenge speciesism more strongly (Singer, 1975; Rosenfeld, 2019b). In either case, the extent with which animal-product consumption is avoidable in practice remains open for empirical research. Although it is clear that omnivores may resist dietary change due to a wide variety of factors, our article elaborates on one potent motivational barrier: identity.

More recently, there has been an increased attention on the influence of social identity on attitudes toward meat reduction and veg*nism, for example by considering the influence of political identity (Dhont and Hodson, 2014), gender (De Backer et al., 2020), species (Leite et al., 2019) and cultural identity (Ruby et al., 2016). Social identity refers to one’s self-perception based on feelings of belonging to a particular social group (e.g., conservatives, females, humans) (Tajfel, 1972; Turner and Reynolds, 2010). According to social identity theory (Tajfel and Turner, 1979, 1986), people are able to flexibly construe themselves as individuals or group members across situations, depending on perceived similarities and differences in a social comparison context (Turner and Reynolds, 2010; Hogg, 2016). The theory postulates that people desire a positive and distinct identity which, through social comparison and identification, could explain why people are motivated to favor their own ingroup (i.e., ingroup favoritism) and discriminate against outgroups, even when they are categorized based on minimal criteria (e.g., preferring a painting of Klee vs. Kandinsky) (Abrams, 2001; Otten, 2016). Given that the mainstream ideology (called “carnism”) legitimizes the consumption of animal products (e.g., as normal, natural, and necessary) (Joy, 2009, 2018) and delegitimizes veg*n minorities and veg*n practices (Joy, 2009, 2018), the omnivorous majority may resist changing their diet because they are motivated to protect their identity as consumers of animal products when confronted with an “outgroup” of veg*n advocates. What is currently missing in literature, however, is a comprehensive account of how ideological resistance to veg*n advocacy can be traced back to identity-based motivations.

As a minority (Martin et al., 2008), veg*ns are a numerically small group (about 2–10% in Western countries; Corrin & Papadopoulos, 2017) who typically hold moral, antinormative positions. Although veg*ns may have various motives for their diet – such as taste preference, religious or political beliefs, upbringing, influence of family and friends, and financial constraints (Ruby, 2012; Rosenfeld and Burrow, 2017), the three most common veg*n motives in Western countries include concerns about animal, environmental and health (see §1.1) (Janssen et al., 2016; Rosenfeld, 2018; Hopwood et al., 2020). These three motivations often co-occur (Janssen et al., 2016; Trethewey and Jackson, 2019) and may form a hierarchy with “more moral” motivations being viewed more positively (i.e., concerns about animals followed by environmental and then health concerns), especially among vegans (MacInnis and Hodson, 2021).

Because veg*ns often decide to consciously deviate from carnist norms based on strong moral motivations, they tend to strongly internalize their diet as an important aspect of who they are (Rosenfeld and Burrow, 2018; Rosenfeld, 2019b) and as a part of their moral identity (Chuck et al., 2016; Feinberg et al., 2019), i.e., their identity as a morally committed person and associated thoughts, feelings, and behaviors with regard to promoting or protecting the welfare of others (Aquino and Reed, 2002; De Groeve and Rosenfeld, 2022). The labels “vegetarian” and “vegan” may be a source of ingroup pride (Rosenfeld, 2018), facilitate cooperative group formation (Smaldino, 2019) and moral identity signaling (Aquino and Reed, 2002; Paxman, 2016), so that omnivores may readily perceive veg*ns as morally committed advocates who attract attention for “their” cause (Markowski and Roxburgh, 2019; De Groeve et al., 2021).

Indeed, there are a lot of actions veg*ns may partake to promote their diet and moralized identity, such as sharing messages on social media, signing petitions, donating money to campaigns and/or protesting (Thomas et al., 2019). Veg*ns may participate in various education and community engagement – from cooking and sharing veg*n food with others, to writing books or articles, to engaging in outreach (e.g., giving lectures, advertising stalls) (Chuck et al., 2016; Paxman, 2016). Yet, there is a lot of heterogeneity in how veg*ns construe their identity and engage in different forms of advocacy (Chuck et al., 2016; Paxman, 2016; Thomas et al., 2019). While only a radical minority engages in illegal actions such as clandestine investigations and animal rescue operations in pursuit of social change (Thomas et al., 2019), many veg*ns may detach from the veg*n label in some circumstances, see it as a personal burden, and are reluctant to discuss their dietary preferences with others (Chuck et al., 2016; Paxman, 2016; Rosenfeld and Tomiyama, 2019).

Based literature on veg*ns’ main motives and collective goals (MacInnis and Hodson, 2021; De Groeve and Rosenfeld, 2022), we presuppose that veg*n advocacy primarily involves claims that animal-product consumption harms animals, while claims about environmental and/or health harms are secondary. Stronger moral convictions, a stronger rejection of carnist and speciesist majority beliefs and a higher perceived inconsistency between moral vs. majority beliefs may motivate activism (Piazza et al., 2015; Harrington et al., 2022). In addition, Judge et al. (2022) showed that more principled convictions predict engagement in vegan advocacy via a stronger identification with other vegans and animals, perceived collective efficacy and moral outrage. Although pragmatic veg*n advocates may welcome incremental dietary changes (i.e., eating less meat/animal products rather than none) based on various motives, the desire to communicate a clear moral identity with consistent goals may cause veg*ns to dissociate from other self-identified veg*ns who do not share the same motives (e.g., categorizing health-motivated veg*ns as merely plant-based dieters) or calls for change (e.g., dismissing incremental changes as hypocritical) (Leenaert, 2017; MacInnis and Hodson, 2021; De Groeve and Rosenfeld, 2022). Advocates who clearly signal a moral identity are likely to evoke carnism-induced ideological resistance among members of the omnivorous majority (De Groeve and Rosenfeld, 2022; De Groeve et al., 2022).

Although humans have gradually included meat in their diet over evolutionary history, the prevalent consumption of animal products only became the norm in Western countries over the last century (Graça, 2016; Chiles and Fitzgerald, 2018). Joy (2009) introduced the term “carnism” to refer to the normative belief system that legitimizes animal-product consumption as a given rather than a choice, rendering associated harms “invisible.” Indeed, many people nowadays are socialized to adopt a diet rich in animal products as a part of their identity, which is by default deemed appropriate and therefore unlabeled (Bastian and Loughnan, 2017; de Boer et al., 2017). Consequently, omnivores generally do not consider their diet as a central aspect of who they are or take pride in their diet (Piazza et al., 2015; Rosenfeld and Burrow, 2018). Although omnivores generally care about animal welfare and, to some extent, the environment (Trethewey & Jackson, 2019), they tend to dissociate these values from their dietary pattern (Lacroix and Gifford, 2019; Rothgerber, 2020) and do not report prosocial/moral motives to follow their diet (Rosenfeld and Burrow, 2018). The most common reasons for eating meat include taste, habit, upbringing, convenience (e.g., socially, practically, financially), and perceived health of eating meat (Povey et al., 2001; Mullee et al., 2017; Lacroix and Gifford, 2019). Compared to veg*ns, omnivores are moderately more likely to endorse conventional values that bind groups together, including power/authority, loyalty and purity (Graham et al., 2013; Grünhage and Reuter, 2021; Holler et al., 2021).

Because the omnivorous diet is conventional, majority norms exert a strong immediate influence on omnivores. One reason for majority’s social power is that majority membership protects against social rejection (Martin et al., 2008): eating and sharing animal products is a way to facilitate social bonding and different animal foods may characterize different nations (e.g., Australian meat pies), celebrations (e.g., Thanksgiving Turkey) or (sub) cultures (Markowski and Roxburgh, 2019; Nguyen and Platow, 2021). For example, in Western countries many people love dogs and eat pigs (Joy, 2009), while eating dogs may be acceptable in some Asian countries (Podberscek, 2009) and eating pigs is forbidden by Islamic and Judaic scripture (Farouk et al., 2015). Majorities also exert a powerful influence because individuals may doubt their own convictions in the face of the majority (Martin et al., 2008; Bolderdijk and Jans, 2021; May and Kumar, 2022). Conforming to majority norms (e.g., eat what your peers eat) enables fast and frugal decision making, obviating the need for individuals to extensively deliberate on food choice (Henrich et al., 2001). Unsurprisingly then, one of the most persistent barriers to follow more plant-based diets are conformity pressures (Ruby, 2012; Leenaert, 2017; Lacroix and Gifford, 2019).

Conformity pressures may explain why meat reduction initiatives may evoke considerable resistance (Morris et al., 2014) and why omnivores often report having experienced conflict with veg*ns, who oppose the majority’s carnist ideology (Guerin, 2014; Piazza et al., 2015; Markowski and Roxburgh, 2019). Conversely, veg*ns can be targets of anti-veg*n bias (Earle and Hodson, 2017) such as social stigma and negative stereotypes (Chin et al., 2002; Minson and Monin, 2012; MacInnis and Hodson, 2017; Markowski and Roxburgh, 2019; De Groeve and Rosenfeld, 2022). Joy (2018) distinguishes two sets of psychological defenses people use to maintain animal-product consumption and resist change, which we refer to as “carnist resistance”: (1) defenses that legitimize the consumption of animal products (i.e., pro-carnist defenses) and (2) defenses that delegitimize veg*nism (i.e., counter-veg*n defenses). These two defenses resemble a tendency of people to selectively seek and process information that confirms one’s identity or position (i.e., confirmation bias), while being disproportionally more critical of refuting information (i.e., disconfirmation bias; Taber and Lodge, 2012). At the same time, it is important to note that defensive and stigmatizing attitudes are dynamic and may vary considerable across individuals, cultures and contexts (Paxman, 2016; MacInnis and Hodson, 2017). Individual variation and the versatility of the human mind (e.g., identities, language) through time should prevent us from essentializing identity categories. As we analyze carnist resistance further, we will consider more variety among omnivores in how they might respond to veg*n advocacy.

Most research that examined carnist resistance until now has relied on cognitive dissonance theory (Festinger, 1962) to explain the maintenance of meat consumption as a morally-conflicting behavior (i.e., the meat paradox) (Bastian and Loughnan, 2017; Lin-Schilstra and Fischer, 2020; Rothgerber, 2020). Cognitive dissonance refers to a state of negative arousal that arises when someone holds two contradictory cognitions, typically involving a behavior versus an attitude (e.g., eating meat but caring for animals). Subsequently, individuals are motivated to resolve this perceived inconsistency either by changing one’s behavior (e.g., refusing to eat meat) or by changing one’s attitudes (i.e., defending meat consumption).

In our account of carnist resistance, we draw on revisions of cognitive dissonance theory that integrate the role of identity or the self-concept (Cooper, 2007). Self-based revisions of dissonance theory assert that perceived attitude-behavior inconsistencies do not just arouse dissonance due to a perception of inconsistency between two cognitions (Festinger, 1962), but that dissonance only occurs to the extent that it involves a threat to the self (Cooper, 2007): When a behavior is perceived as contradicting one’s self-concept in Aronson’s (1968) self-consistency account, or when it challenges one’s self-integrity as a moral and competent person in Steele’s (1988) self-affirmation account. These accounts are in line with the postulate that humans desire a positive and distinct identity (Hogg, 2016). Consequently, omnivores are likely to experience self-threat when veg*n advocates signal a moral identity by claiming that animal-product consumption entails avoidable harm. More specifically, such an exposure may readily threaten omnivores’ own moral identity (Bastian and Loughnan, 2017; De Groeve and Rosenfeld, 2022). In addition, although omnivores generally view eating animal products as a given and not as central to their identity (Joy, 2009; Rosenfeld and Burrow, 2018), a confrontation with veg*n advocates may increase the salience of omnivores’ carnist identity – their identity as consumers of animal products (or non-veg*ns) and the thoughts, feelings and behaviors associated with it (De Groeve and Rosenfeld, 2022). Based on this theorizing, Minson and Monin (2012) their measure of anticipated moral reproach (e.g., “If they saw what I normally eat, most vegetarians would think I am extremely (im)moral.”) can be construed as a proxy of moral/carnist identity threat and the meat paradox can be construed as an inconsistency between omnivores’ moral and carnist identity, which omnivores are motivated to resolve in order to maintain a positive identity and avoid dissonant feelings of self-threat. Our theorizing is also consistent with the New Look model of dissonance, according to which individuals reduce dissonance to render consequences of behavior non-aversive (Cooper, 2007).

Based on research on the meat paradox, meat-related dissonance (e.g., Bastian and Loughnan, 2017; Rothgerber, 2020), moral disengagement (Graça et al., 2016) and research on identity-protective and motivated cognition (Kunda, 1990; Kahan, 2013; Williams, 2020; May and Kumar, 2022), a distinction can be made between two broad categories of pro-carnist defenses omnivores employ to resolve moral/carnist identity threat: (1) motivated reasoning and (2) motivated ignorance. Below, we will shortly discuss these motivated defenses and clarify their interrelationship with counter-veg*n defenses in the form of negative stereotyping and stigmatization. We note that our discussion is mainly focused on defenses against animal welfare claims because these embody the primary motive for veg*n advocacy (MacInnis and Hodson, 2021) and have been studied most extensively. In addition, environmental and especially health claims pro veg*nism may be less persuasive or arouse less dissonance (De Groeve and Rosenfeld, 2022; Silva Souza and O’Dwyer, 2022).

Omnivores who are already committed to their diet and have a stronger carnist identity (typically more meat-attached, conservative, traditional men, speciesist and/or proud of their cultural identity) are more likely to actively defend themselves through motivated reasoning and negative stereotyping of veg*ns, which reinforces the idea that eating (more) plant-based is difficult (Graça et al., 2016), pointless and “not for me” (Oyserman, 2015). By rejecting claims against the consumption of animal products, omnivores may strengthen their commitment to eating animal products and their aversion for veg*nism (Bastian and Loughnan, 2017; Rothgerber, 2020). This individual-level polarization may spur group-polarization in society at large if omnivores publicly rationalize their diet and derogate those who oppose it, because in doing so, they may potentially recruit others to share and reinforce the carnist majority position (Kahan, 2013; Bastian and Loughnan, 2017). Omnivores with a weaker carnist identity (more likely less meat-attached or flexitarian, more liberal, less masculine and more feminine, higher solidarity for animals and less attached to cultural norms) are less likely to actively defend their diet; motivated ignorance and passive forms of veg*n stigmatization (e.g., avoidance) may suffice. These indirect defenses allow omnivores to ignore veg*n advocates’ claims, so that they remain ambivalent about the consumption of animal products (Rothgerber, 2020).

Overall, these findings are remarkably consistent with studies on minority influence (Moscovici, 1985; Mugny and Pérez, 1991; Martin et al., 2008; Levine and Tindale, 2014) showing that minority’s calls for change often evoke immediate defensiveness or only ambivalence. As a result, the influence minorities exert on majority members is usually non-existent or even negative at a direct, manifest level (Moscovici, 1985; Mugny and Pérez, 1991; Wood et al., 1994). This does not mean, however, that minorities exert no influence at all (Mugny and Pérez, 1991; Wood et al., 1994). In Western countries, the market of plant-based alternatives is growing and majority norms are gradually shifting as flexitarianism is gaining popularity and veg*nism is increasingly accepted (Vranken et al., 2014; Lundahl, 2020; Verain et al., 2022). Consequently, it may become increasingly difficult to defend animal-product consumption and advocates may become more influential (De Groeve and Rosenfeld, 2022). Both research on minority influence and cognitive dissonance suggests that omnivores may resolve moral/carnist identity threat by adopting a third dissonance-reducing strategy: committing to behavioral change.

Omnivores may (privately) accept claims that animal products entail avoidable harm (e.g., to animals, the environment) and might reduce dissonance by aligning their dietary behavior more with their moral identity and principles (Feinberg et al., 2019; Bouwman et al., 2022; De Groeve and Rosenfeld, 2022), thus rejecting animal-product consumption at least partially by making shifts toward veg*n diets (Rothgerber, 2020). One recent study (Silva Souza and O’Dwyer, 2022) found personal health arguments with a mixed recommendation (i.e., to reduce or eliminate animal products) could not persuade people to eat less animal products, but that arguments related to animal rights and environmental welfare were effective to increase omnivores’ willingness to reduce (not cease) animal-product consumption via elevated dissonance. In addition, participants exposed to environmental arguments were more likely to disagree with ceasing animal-product consumption. Arguably, health arguments do not consistently favor veg*n dieting (i.e., omnivorous diets can also be healthy), while environmental arguments appear less stringent and animal rights favor veg*n diets most consistently.

A meta-analysis of minority influence research suggests that consistency is especially important for minorities to exert influence (Wood et al., 1994). Not only does consistency allow to capture attention of the majority (Wood et al., 1994), it also allows to signal that the majority behaves inconsistently (Wrenn, 2018), should rethink their position and change their behavior to the minority position (Mugny and Pérez, 1991; Wood et al., 1994). Given that veganism is a consistent anti-speciesist position (Bruers, 2021), this might explain why animal-welfare interventions with a “go vegan” recommendation may have larger effects on meat reduction than more modest recommendations (“go vegetarian” or “reduce your consumption”) (Mathur et al., 2021). Similarly, Dakin et al. (2021) found that prescribing vegetarian (vs. flexitarian) diets for a week based on animal welfare arguments led to larger sustained reductions in meat intake, which was partially mediated by reduced 4Ns rationalization and commitment to eat meat. It is important to note, however, that participants in the studies above were probably already more receptive to eating less meat. As differences in opinion increase, a more flexible (vs. uncompromising) style of negotiation becomes more important for a consistent minority to exert influence (Mugny, 1975; Mugny and Pérez, 1991; Leenaert, 2017; Weiper and Vonk, 2021).

Minority influence research further suggests that conversion to a minority position is often delayed (rather than immediate) and typically happens after a validation process where majority members actively thought about the minority’s claims (Moscovici, 1980; Mugny and Pérez, 1991; Wood et al., 1994). Likewise, veg*ns typically report that they changed gradually in different stages (Chuck et al., 2016; Grassian, 2019; Bryant et al., 2022). Highlighting the role of motivated resistance, Bryant et al. (2022) provide an overview of psychosocial barriers to overcome in the journey to ethical veganism through five stages of change: precontemplation, contemplation, preparation, action, and maintenance. Consumers who reject rationalizations for eating animal products may become more ambivalent about eating meat and negative about conventional meat production systems (Berndsen and Van Der Pligt, 2004; Hartmann and Siegrist, 2020). Although they might initially be motivated to ignore claims against consuming animal products, they may be more open to eat meat alternatives (e.g., Quorn, tofu, seitan) (Hartmann and Siegrist, 2020) and change their diet after effortful information seeking if concerns about eating animal products can no longer be ignored (Rothgerber, 2020; Pauer et al., 2022). Based on interviews with veg*ns, this information may include a variety of sources, such as educational materials (e.g., documentaries, books, flyers, speeches), role models and emotionally intensive imagery related to animal cruelty (Chuck et al., 2016; Grassian, 2019).

Reducing carnist resistance seems crucial to promote dietary change among omnivores. As people reject carnism more, eat less meat, follow a flexitarian diet longer, and see avoiding meat as more self-defining, they are more likely to identify with vegetarians rather then meat-eaters (Rosenfeld et al., 2019) and less likely to negatively stereotype veg*ns as socially unattractive (Minson and Monin, 2012; De Groeve et al., 2022). A rejection of carnism is also strongly associated with more positive and less speciesist attitudes toward animals, feeling more guilty about eating animal products, and being more engaged in animal advocacy (Piazza et al., 2015; Monteiro et al., 2017; Rosenfeld, 2019b; Amiot et al., 2020). If moral reasons for veg*n diets are internalized, people are likely to develop disgust toward the idea of eating animal products (Rozin, 1996; Graça et al., 2016) and if eating veg*n diets feels identity-congruent, perceived difficulties in veg*n practice may be interpreted as worthwhile and meaningful (Oyserman, 2015). Nevertheless, important barriers for adopting veg*n diets (e.g., conformity, meat attachment, health concerns, practical convenience) may also cause a significant number of veg*ns to lapse or revert from veg*n diets temporarily or permanently (Rosenfeld, 2018; Salehi et al., 2020). Conversely, veg*ns are more likely to maintain their diet if they have social support, if they are motivated by animal ethics, if they have knowledge about veg*n nutrition and if it is practically feasible and affordable (Ruby, 2012; Salehi et al., 2020).

First, our account presupposes that veg*n advocacy is based on claims that animal-product consumption is harmful and avoidable. Future research could test to which extent veg*ns (vs. omnivores) perceive different non-veg*n diets and/or animal products as harmful (e.g., to animals, the environment, health) (e.g., Schein and Gray, 2015) and avoidable (e.g., by measuring “outcome efficacy”; Steg and de Groot, 2010). We expect that veg*ns are more likely to construe their diet as a part of their moral identity due to perceiving more avoidable animal harms, followed by environmental and health harms, respectively. More research is required to examine how veg*n dietary motivations (e.g., Hopwood et al., 2020, 2021b) contribute to moral identity internalization, as well as a desire to signal one’s moral identity (Aquino and Reed, 2002) via veg*n advocacy (e.g., Thomas et al., 2019; Judge et al., 2022).

Our account suggests that moral identity signaling among advocates may threaten omnivores’ moral and carnist identity simultaneously, and claims against animal-product consumption that are perceived as more harmful and avoidable are expected to arouse a stronger moral/carnist identity threat (e.g., by measuring “moral reproach”; Minson and Monin, 2012) and dissonant feelings (e.g., Silva Souza and O’Dwyer, 2022) among omnivores, especially among those with stronger moral and carnist identities. Future research could examine whether the strength of omnivores’ moral and carnist identity moderates threat perceptions of advocacy (see De Groeve and Rosenfeld, 2022) and also consider environmental and health harms related to various animal products as potential causes of dissonance besides animal harms related to meat in particular (Rothgerber, 2020; De Groeve and Rosenfeld, 2022; Silva Souza and O’Dwyer, 2022). Concerning moral identity, we acknowledge that people’s conceptions of what is “moral” may vary considerably, depending on various cooperative relationships (Curry et al., 2019), the endorsement of conventional values (i.e., authority, loyalty, purity) (Graham et al., 2013) and divine authority (Simpson et al., 2016). Although some research suggests that moral identity (Dawson et al., 2021) and moral judgment processes can be largely attributed to concerns about (intentional, unjustified) harms (Schein and Gray, 2015, 2018; Sousa et al., 2021), different moral paradigms may affect how people respond to veg*n advocacy (e.g., Grünhage and Reuter, 2021). Similarly, omnivores may vary considerably in how they construe their carnist identity, depending on the individual, culture, and the particular context in which it is cued (Turner and Reynolds, 2010; Oyserman, 2015). Pursuing a more comprehensive, multifaceted understanding of carnist identity, for example by conducting segmentation studies (e.g., Lacroix and Gifford, 2019; Verain et al., 2022), is recommended. Carnist resistance (i.e., pro-carnist and counter-veg*n defensiveness) is relevant to consider in this regard (see Table S2 for existing measurement scales).

Based on our account, we expect that a stronger carnist identity positively predicts motivated reasoning, negative stereotyping of advocates, and commitment to eat animal products. More research could test whether motivated reasoning negatively predicts perceived harms and the perceived efficacy of veg*n diets to avoid harms, and whether different rationalizations for eating animal products (e.g., the 4Ns) support different negative stereotypes (e.g., veg*ns seen as contradicting the 4Ns). Conversely, omnivores with a weaker carnist identity should be less likely to rationalize animal-product consumption or actively stigmatize veg*ns by expressing negative stereotypes (though still more likely than veg*ns), and mainly rely on motivated ignorance. Researchers may examine whether different forms of motivated ignorance (e.g., ignoring farmed animal suffering) inform different stigmatizing attitudes (e.g., avoiding contact with veg*ns). Although relevant scales to measure stigmatization exist (Table S2), future research is needed to examine whether passive forms of stigmatization can be distinguished from negative stereotyping. We also recommend more psychometric analysis to better understand the interrelationship between pro-carnist defenses: for example, our conceptualization of neutralization as a form of motivated ignorance is rather tentative and the status of dichotomization is also less clear (Hartmann and Siegrist, 2020; Rothgerber, 2020). In addition, future research could assess the relative importance and interrelationship between personal and social motivations linked with one’s carnist identity related to individual meat attachment and healthy eating, politics (e.g., conservativism), gender (e.g., new/traditional masculinity), species (e.g., human supremacy) and culture (e.g., nation, religion) (see studies in §2.2.5 for measurement scales) and how these identities inform pro-carnist and counter-veg*n defenses. Lastly, research on how these defenses are associated with an ambivalence about or a commitment to animal-product consumption is recommended. For example, previous research has found both committed and ambivalent omnivores may be motivated to ignore/downplay the sentience of farmed animals (Buttlar and Walther, 2018; Leach et al., 2022), which might be due to differences in moral/carnist identity threat. Committed omnivores may ignore information due to indifference (i.e., low moral, high carnist identity threat), while ambivalent omnivores may want to avoid confrontation (i.e., higher moral identity threat) (Onwezen and van der Weele, 2016; Rothgerber, 2020), though this needs to be verified.

Our account further suggests that an apparent resistance against veg*n advocacy may mask indirect, private influence, often at a later point in time. Therefore, future research on veg*n advocacy would benefit from integrating minority influence perspectives (Martin et al., 2008; Levine and Tindale, 2014), ideally using longitudinal designs to capture delayed influence across different stages of change (Bryant et al., 2022; De Groeve and Rosenfeld, 2022). More diverse quantitative and qualitative research approaches (e.g., field experiments, participant observation) are also recommended to demonstrate potential differences between publicly expressed and privately held beliefs (cf. pluralistic ignorance) (Bolderdijk and Cornelissen, 2022; De Groeve and Rosenfeld, 2022). In addition, our account suggests that the rejection of carnist beliefs is an important predictor of accepting commitments to dietary change (Rosenfeld et al., 2019; Trethewey and Jackson, 2019). Future research could thus develop interventions that target pro-carnist defenses, for example within an open, respectful dialogue (Buttlar et al., 2020). Although experimental studies have manipulated variables related to social norms and motivated ignorance such as dissociation and dichotomization (Mathur et al., 2021; Kwasny et al., 2022), experiments on how to tackle specific rationalizations (e.g., nice, natural, necessary, human supremacy, faith) and denial of harms are missing (Rothgerber, 2020; Kwasny et al., 2022). In addition, researchers could examine how to reduce negative stereotyping of vegan advocates, moralistic stereotyping in particular (for a review, see De Groeve and Rosenfeld, 2022).

Because our account suggests that promoting veg*n diets might increase polarization, we also recommend researchers to examine more pragmatic approaches to support change (De Groeve and Rosenfeld, 2022), for example by addressing the practical barriers (e.g., capacities, opportunities) that make changing one’s mind costly (Graça et al., 2019; Williams, 2020). For committed omnivores, the promotion of small dietary changes within meat formats that are already familiar (e.g., meat substitution) seems promising (Lacroix and Gifford, 2020). Emphasizing similarities between omnivores and veg*ns might also improve intergroup relations, trust and credibility (De Groeve and Rosenfeld, 2022), which could be examined using common and dual identity approaches (Gaertner et al., 1994; Dovidio et al., 2007). For example, to tackle human supremacy, advocates may emphasize commonalities (e.g., most people find factory farming problematic) and group differences (e.g., vegan diets minimize animal abuse) within a shared social identity (e.g., humans). To appeal to conservatives, veg*n advocates could argue that factory farming is untraditional and that environmental protection is patriotic (Rothgerber, 2020; Grünhage and Reuter, 2021). “Masculine” males may be motivated to challenge majority norms by emphasizing norms of responsibility, rebellion, and strength (Rothgerber, 2013). In addition, future research could examine the promotion of veg*n diets as a way to reclaim individuality: One does not have to identify with a particular group (veg*n or omnivore, male or female, liberal or conservative, etc.), in order to reflect on whether one’s diet violates one’s moral values (Bruers, 2021; Bouwman et al., 2022).

Although our account addresses resistance among omnivores against veg*n advocates, we also recommend future research to assess how motivated cognitions affect veg*ns’ commitment to their diets. Like omnivores, veg*ns may too eagerly embrace or suppress information that strengthens or protects their (moral) identity, for example by believing that humans are “naturally” herbivores, that non-veg*ns cannot care about animals or by denying that omnivorous diets can be healthy (van der Weele, 2013). Conversely, veg*ns may also comply with carnist norms in social situations if they experience stigma (Rosenfeld and Tomiyama, 2019; Bolderdijk and Cornelissen, 2022), for example by framing their diet as a requirement (e.g., allergies) rather than a (moral) choice or identity (Paxman, 2016; Rosenfeld and Tomiyama, 2019).