Social Proof

[Last Updated January 21st 2024]
Social proof is a heuristic where we look to the actions of others to determine how to behave or what decisions to make, especially in ambiguous social situations where we aren’t quite sure of what to do. The term was created by Robert Cialdini (1985) in his book Influence: Science and Practice. However, the research behind it goes back to the 1930s and was especially prominent following World War II, as researchers attempted to understand how so many individuals could condone the atrocities of the war by studying the influence of authority, conformity, in-group-out-group bias, and herd behaviour (all of which influence social proof). In one of the most famous early social influence studies, Sherif (1935) had participants judge how far a dot of light moved while in a completely dark room. As a result of the autokinetic effect (where a small point of light in darkness appears to move, such as a star in the sky) participants estimated some amount of movement even though the light was always stationary. They did this 100 times, so that experimenters could determine a range and average movement measurement for each individual (e.g. 2 to 8 inches with a median of 5.45). They also ran this study on four participants, who performed the task on three separate days, and determined an individual’s range and median tended to persist over time. Sherif (1935) then performed a second experiment where participants either began making estimates in a group, or by themselves, and then switched (e.g. started by themselves, then switched to a group). Each participant was involved in 3 group sessions and 1 individual session, split over four days. Those who started in group sessions saw a quick convergence of range and mean, which lasted across all 4 days and into the final individual session. Those who started with an individual session converged towards a common range and mean once they joined a group, starting far apart from one another and moving incredibly close together by the fourth session. Thus, there seemed to be clear evidence that individuals estimations of an ambiguous value were influenced by the estimations of others. Asch (1951) ran a similar study to examine the power of social influence, by having participants perform a vision test with a group of confederates (actors who were in on the study) pretending to be other participants. Participants alongside confederates were shown a target line, and then three lines (A, B, and C) and asked to state out loud which of the three lines were the same length as the target line. The answer was always obvious. However, the confederates were instructed to give wrong answers on 12 of the 18 trials, and the participant was always the last to provide their answer. Therefore, the participants were faced with a situation where they thought a specific answer was correct, but where everyone else gave a different answer. In respect to the 12 trials where individuals were faced with a wrong answer from the group, 74% of participants conformed to the wrong answer at least once. Further, one-third of participants conformed to the error in 6 or more of the 12 trials. This once again demonstrates that group norms (social factors) can have a clear influence on decision making. However, Asch (1951) made a point of clarifying that 26% of participants never conformed, and that many participants only conformed a few times. Asch conducted many more experiments finding similar results (Asch, 1955, 1956), including one in partnership with the show Candid Camera that you might see replicated on TikTok where confederates (actors) standing backwards on an elevator (not facing the door) influence others who enter the elevator to conform and stand backwards (Search for “Asch elevator video” on YouTube for the original Candid Camera clip where this experiment was carried out). One interesting finding however was that when a participant no longer had to publicly state their answer, they were considerably less likely to conform to the majority when they knew the majority was wrong (Asch, 1956). Deutsch and Gerard (1955) also tested this by examining whether the dominant social influence behind behaviour changes in Asch’s (1951, 1955) experiments were normative (e.g. to conform with a group) or informational (e.g. because they believed the other’s might be correct). They ran a study similar to Asch’s (1951) line study, but removed the normative component by having participants make decisions by pressing a button while partitioned off from others in the room (so others would not know their choice). Much like in Asch’s (1956) study, participants were less likely to conform than those in the normative condition, but still more likely to conform than those outside a group. Thus, they suggested individuals were influenced by both normative and informational social influence. The takeaway here is that even if someone doesn’t agree with a social norm, they may publicly express their agreement (e.g. on social media) to conform to group expectations (which can be leveraged in marketing strategy). And they may even shift their beliefs, if they believe that those expressing different opinions than their own are competent or have some sort of expertise that they lack.

There are a number of different domains where social proof regularly influences consumer decision making, such as reviews, social media engagement, influencer marketing, etc. However, the power of social proof differs across domains, and the best ways to leverage social proof differs depending on the product/service, existing technologies, and current trends. For example, a meta-analysis by Floyd et a. (2014) found that critic reviews on third-party websites were the most impactful review type on sales. However that meta-analysis considered studies going as far back as 2004, when social media had yet to become globally popular. Today, most customers read product reviews on websites like Amazon before making a purchase. For larger purchases (like high-end electronics, cars, appliances, computers, and phones) many consumers seek out the aforementioned third party websites (or YouTube channels) with independent critics who examine every aspect of various products, and compare and contrast them with one another. On the other hand, many customers rely on their favourite influencers to review products, and assume that even if the influencer is paid, they must love the product or they wouldn’t have accepted the deal. In fact, one of the first things many influencers say at the start of a paid-promotion is that they used the product/service before they starting profiting from advertising it. And influencers (especially celebrities) can lead to sales of products just by mentioning they use them. For example, in 2019 when Jungkook from BTS mentioned he used Downy Fabric Softener, the product instantly sold out, leading to countless online memes (Koreaboo, 2019). In fact, influencers and celebrities are not even needed to provide social proof for products. Many products go viral organically in different online communities. Rather than post examples, we suggest you google “books that went viral on TikTok” or “trending #cleantok products” to see the latest trends. Of course, with the right influencers and the right branding, a skilled marketer can help start these organic trends. In the past we would have also included a section on demographic differences in social proof. For example, a study from 20+ years ago by Mangleburg et al. (2004) found that teens spent more money when shopping with friends due in part to social proof (specifically informational social influence that helps teens navigate ambiguous shopping situations). Informational social influence occurs when we conform to others because we believe they are competent, which is different from normative social influence where we conform to be similar to the group. And in the past, we often focused research on teenagers and adolescents who lack life experience and often rely on other’s expertise. But today almost everyone who is active on social media is susceptible to social influence (both informational and normative) and social proof. Without any effort or intent to seek out the information, social media algorithms feed us social proof from others, whether in the form of advice, reviews, entertainment, news, or advertisements. Even when using rideshare apps, food delivery apps, house rental apps, etc, we consistently rely on social proof indicators like reviews and ratings to determine what options to choose.

Applying Social Proof to Marketing

Unless you don’t need to seek out customers or clients, social proof is always an important consideration for your business. For B2B marketing, social proof is best expressed through case studies and reviews that reference industry-relevant customers/clients. However, online courses, videos, published articles (including on Medium), podcasts, and popular blogs can also generate social proof if potential customers/clients are able to see the audience metrics. For example, if you run a B2B firm that sells server management services, having popular YouTube videos (or a subscriber account in the 1000s) that teach people how to set up servers demonstrates expertise, and suggests that others in the industry trust you as a source of knowledge. This in turn acts as tacit social proof that your B2B firm is competent. BTC marketing is a bit more complex. Influencers are always one of the best sources of social proof, provided that the influencers you work with have the trust of their viewers (usually measured through engagement metrics rather than views). And reviews of your product or service come in at a close second. In some industries, third party reviews are important, and you’ll want to send third party reviewers your products while creating a great impression at the same time. For example, many consumers look to third party reviews before buying any computer hardware, and consider technical aspects/metrics they wouldn’t be able to find elsewhere (e.g. monitor black levels or graphics card ray tracing performance). On the other hand, consumers often look at product reviews before purchasing general consumer goods like toothpaste or chocolate bars, especially when ordering online. Clothing purchases on the other hand are often influenced by fashion vloggers and influencers, rather than direct consumer reviews. It can be helpful to discover how your competitors or potential alternative brands/products utilize social proof across their brand presence to determine what domains may be important to your marketing strategy. Once you have an idea of what domains are important, you should consider how you can communicate that others value your product/service. And you should also learn the relative importance/weight of those different communication avenues through A/B testing, as well as their impact on sales (or whatever goal you may have). For example, if you use social influencers, you can provide them with a discount code for their viewers, so that you can track the number of sales they generate. With a good data analytics setup, you can also determine if users who entered that code (or started on a landing page tagged with a code referencing the influencer) spent time looking at reviews of the products they purchased. You may find out that social proof from influencers leads consumers to ignore other’s reviews when making a purchase. Or you may find out that individuals care about both social influencers and reviews from other customers. All of this will require ongoing experimentation. And the effectiveness of social proof sources is likely to change over time as online trends shift. Also keep in mind that social proof is most effective in ambiguous situations (e.g. when a consumer isn’t sure about what the price of a product should be). If you are creating a new brand, you can manufacture ambiguity and leverage social proof. One great example of this comes from a marketing stunt by Payless ShoeSource, who opened a fake luxury shoe store in 2018 for one day called Palessi and invited numerous influencers who were then willing to pay prices up to $640 for shoes that normally sell for between $20 and $40 at their Payless stores (see and Much like in the experiments by Asch (1951; 1955; 1956) influencers invited to the event likely behaved as though the shoes must be high quality because all the influencers around them were behaving that way.

Practical Examples of Social Proof

Creating Social Norms with Social Proof

Imagine you just released a new videogame or app, and you want to convince the online world that it’s amazing. One way to accomplish this is to construct a social norm on social media regarding your game/app. For example, before anyone else can play/use it, make sure influencers are promoting and praising it on social media. This will act as social proof, which in turn may potentially influence how your users feel about the game/app, or how they publicly discuss it. Even if they only find it to be average, if everyone else is praising it, many people will jump on the bandwagon and praise it as well. This in turn will create even more social proof, which in turn will lead to more positive engagement with your game/app. And in the end, you will have constructed a cycle of positive attention that validates a social norm which benefits your brand. This is incredibly relevant on social media. If you view our page on social norms, or read Melnyk et al. (2019), you will see that social norms can impact behaviour in various ways. Keep in mind that this likely won’t work if you’re already a huge brand (unless you manage to buy-off every major influencer in your industry), as there is profit to be made in online criticism. Further, your game/app can’t be terrible, or users will recognize your strategy. This is most effective when you are first launching a game or app to a relatively small audience or niche target market (e.g. less than 100,000 users) and the experience they have with the game/app is either ambiguous or positive.

Leveraging Reviews

Many businesses assume reviews are an organic process, and that they don’t need to play any role in managing them. But this couldn’t be further from the truth. At a bare minimum, you should try to respond to reviews if possible (and when appropriate), and thank the reviewers for their time. Even if a review is negative, letting a reviewer know you appreciate their feedback and will work towards fixing their issues in the future will communicate to others that you care about your customers. The act of having reviews alone tells others that your company is active and can be trusted, especially if most reviews are positive. In many situations, you can leverage reciprocity to generate positive reviews that will act as social proof. One way many companies do this is by providing a financial incentive to leave a review (e.g. $10 amazon gift card). Another way many companies manage their reviews is by using a review service (e.g. paying a company to host the reviews) which often gives them the ability to delete reviews they don’t like, or make reviews they like more salient (e.g. appear at the top of the page). This is a somewhat unethical practice as it defeats the purpose of the review process. But it’s surprisingly common, and it may be hard to compete with a company that uses this strategy if you don’t use it as well. To be clear, companies offering these services will argue they allow their clients to delete reviews to control spam. But marketers tend to recognize the true nature of these services, and many companies take full advantage of them.

Social Proof at Event Booths

One way to leverage social proof at events, tradeshows or conferences where you have a booth is to manufacture some way to keep people at your booth so that others see your booth as more busy, and thus assume you must be offering something interesting or amazing. You can do this through creative engagement that is relevant to your industry or event. For example, if you offer B2B services for a specific industry, you can give people an opportunity to play a five minute game on a tablet related to the industry that is engaging, and gets them a prize. Because it’s short, they will likely have a positive experience. Because they get a prize, they will likely provide you with their email or contact information for future discussions (or sales calls) due to reciprocity. And because you keep them at/near your booth, others will get curious and make a point of checking it out. Keep in mind that one of the issues with this is people skipping your booth due to it being too busy. To remedy this, just make sure you have lots of brand representatives standing around ready to introduce people to your brand/business. And have them stand a bit away from the booth (if possible) so that they can make eye contact with and smile at anyone that seems curious (a social cue that it’s acceptable to come over). Managing the flow of people is a bit of an art, and can take some practice. But this strategy can make your booth the busiest at a convention, which in turn will act as social proof for prospective clients/customers.

Using Social Proof to Set Anchors

If you’re selling a product or service that has an ambiguous value (e.g. fashion), you can use social proof to set an anchor for pricing. Anchors are reference points that can influence our perception or estimate of values. For example, if you are selling street wear, you can have influencers do “try-on haul” videos of your products, mentioning their prices as they try on each piece. This informs their audience of the general value of your brand. For example, you could sell the same hoodie at a $40, $100, or $1000 price point, simply by having your influencers mention the prices on stream or in their videos. You can also do this non-verbally by promoting your brand through key events. For example, if a celebrity wears your brand to a red-carpet event, that acts as non-verbal social proof that your brand has high value, and allows you to price items around $1000 without coming off as a scam. If a customer latches on to an anchor prior to visiting your store or website, that anchor will influence their acceptance of the prices of other goods. For example, if an influencer talks about getting a $40 hoodie from you, it would likely be difficult to sell a $1000 hoodie on your website, as the $40 sets people’s expectations for prices to be near or around that value. This can also be done for products or services without ambiguous values (e.g. if you have many competitors that already set anchor prices for consumers) but requires that you brand your product in a way that differentiates it from existing alternatives. Or put another way, you manufacture the perception of ambiguity through branding and marketing strategy.

Research Example of Social Proof

Charity Lists

Reingen (1982) ran a series of studies that examined the influence of social proof on charitable giving in both student and household populations. In his first experiment, he had experimenters (who were unaware of the experiment) approach same-sex students (e.g. a woman approaching a woman) who were walking or sitting alone on campus and ask them to donate to a heart association. Some students were just asked to donate, while others were shown a list of 8 previous donations while being asked. 25% of students in the non-list condition donated, while 43% of those in the list condition donated, demonstrating that social proof had an impact on willingness to donate (there were no significant differences between the donation amounts). Reingen (1982) then replicated this study with households in a middle class suburban area of Columbia, South Carolina. Once again, those who saw the list were more likely to donate than those who did not (73% compared to 47%). Reingen (1982) then ran a similar study that asked students to donate blood instead of money (a different behaviour), which once again elicited the same findings, with only 3% (one subject) who did not see a list willing to donate, compared to 30% (nine subjects) who saw the list agreeing to donate blood. This experiment demonstrates that simply showing people a list of others who have taken a similar behaviour can influence their decision making.

Works Cited

Asch, S. E. (1951). Effects of group pressure upon the modification and distortion of judgments. In H. Guetzkow (Ed.), Groups, leadership and men; research in human relations (pp. 177-190). Carnegie Press.

Asch, S. E. (1955). Opinions and social pressure. Scientific American, 193(5), 31-35.

Asch, S. E. (1956). Studies of independence and conformity: I. A minority of one against a unanimous majority. Psychological Monographs: General and Applied, 70(9), 1-70.

Cialdini, R. B. (1985). Influence : science and practice. Scott, Foresman.

Deutsch, M., & Gerard, H. B. (1955). A study of normative and informational social influences upon individual judgment. Journal of Abnormal and Social Psychology, 51(3), 629-636.

Floyd, K., Freling, R., Alhoqail, S., Cho, H. Y., & Freling, T. (2014). How online product reviews affect retail sales: A meta-analysis. Journal of Retailing, 90(2), 217-232.

Koreaboo. (2019, January 21). BTS’s Jungkook Accidentally Caused a Fabric Softener Shortage.

Mangleburg, T. F., Doney, P. M., & Bristol, T. (2004). Shopping with friends and teens’ susceptibility to peer influence. Journal of Retailing, 80(2), 101–116.

Melnyk, V., van Herpen, E., Jak, S., & van Trijp, H. C. M. (2019). The mechanisms of social norms’ influence on consumer decision making: A meta-analysis. Zeitschrift für Psychologie, 227(1), 4-17.

Reingen, P. H. (1982). Test of a list procedure for inducing compliance with a request to donate money. Journal of Applied Psychology, 67(1), 110-118.

Sherif, M. (1935). A study of some social factors in perception. Archives of Psychology (Columbia University), 187, 1-60.

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