Ever had a great meal at a restaurant rated four out of five stars, but then had a lackluster meal at another restaurant with the exact same rating? If so, you might have fallen victim to “the positivity problem”: the vast majority of online reviews are positive, but those favorable reviews don’t always translate to real-world quality. “You can have two products with four-and-a-half stars, but they’re not equally good, nor are they equally successful in the marketplace,” explains Derek Rucker, Professor of Marketing at Northwestern University.
Online reviews are everywhere, guiding our choices on everything from electronics to restaurants to novels. Behind the scenes, as a user experience (UX) researcher, I have been hard at work trying to understand how the language used in reviews affects whether they persuade others—and whether they truly reflect a product’s quality. Recent studies by Derek Rucker, Loran Nordgren, and Matthew Rocklage shed light on two key findings. First, when people are motivated to influence others, their reviews become more emotional. Second, it’s not just the number of stars that matters—how we talk about a product can more accurately predict its real-world success.
Imagine you’ve bought a toaster that you genuinely liked. If you’re simply describing its positive traits—maybe it heats evenly, or it looks nice on your countertop—you might write something like, “It’s well-made and easy to use.” But if you’ve been offered a reward for convincing others to purchase that same toaster, you may leave a more general and vague review, calling it “amazing” or even “life-changing.”
In a series of experiments that showed when people are leaving reviews to persuade others, they naturally use more emotional language.
In one study, participants were asked to write a 5-star review about a product—say, a printer—based on a neutral product description. One group was simply told to note the product’s positive qualities; another was told explicitly to persuade prospective buyers. Using a computational tool called the Evaluative Lexicon (EL)—which scores words for positivity (valence), extremity, and emotionality—researchers discovered that people trying to persuade used words with higher emotionality (for example, “delightful” instead of just “useful”).
“We observe that people express more emotion even in categories where that might be odd and potentially less effective,” Rucker explains.
Is this emotional shift deliberate, or does it happen subconsciously? To investigate, the experiments asked participants to describe a novel while simultaneously remembering either a short or a long numeric code. The idea was that if writing more emotional descriptions requires conscious effort, then occupying people’s minds with a difficult memory task would reduce their ability to produce emotive language.
But that didn’t happen. Participants creating descriptions with the objective of persuasion still used more emotional words regardless of their “mental load,” suggesting that the emotional tilt toward persuasion is largely automatic, rather than a carefully considered strategy.
Another striking finding is that people’s emotional approach remains persistent even when they know the audience is unlikely to be swayed by feelings.
In one experiment, participants wrote a positive review of a restaurant. Those who were incentivized to be persuasive still increased the emotionality of their language—even when their target audience was described as “The Society for Applied Rationality and Mathematics.” In other words, even with a clear signal that rational, cognitive arguments might be more persuasive to that audience, participants had a hard time dialing back the emotion.
“You should skew your appeals to be more cognitive, but that does not appear to come naturally to people,” Rucker says. “It goes against these hard-wired associations.”
As a consumer, I’ve often encountered a frustrating pattern - products with glowing star ratings but results that didn’t always meet expectations in reality. This led me to a crucial question: how can I distinguish authentic reviews from incentivized ones? This phenomenon - that most online ratings tend to be overwhelmingly positive, is also called a “positivity problem.” This means that both an outstanding product and an average one could receive four stars, making it difficult for consumers to differentiate between truly exceptional experiences and those that are mediocre.
Over the years, more e-commerce platforms have introduced “Incentivized” tags to indicate when a reviewer received a free product or discount in exchange for their feedback or reviews. I noticed a distinct pattern - these reviews tend to sound neutral, descriptive, and factual rather than personal and enthusiastic.
On the other hand, the most helpful reviews (based on user engagement) were filled with strong emotions, certainty, and personal experience. These reviews didn’t just say a product was “good” but rather how it made the reviewer feel or how it transformed their routine.
I decided to take a closer look at Sephora's product reviews, sorting them by “Most Helpful.” What I found confirmed my suspicion:
This distinction suggests that shoppers gravitate towards emotionally expressive reviews because they feel more trustworthy and relatable.
“Within the sea of positivity, one of the distinguishing factors is how much emotion is conveyed in the review,” Rucker explains.
The Evaluative Lexicon team focuseshg on a specific quality called emotionality. Emotionality distinguishes how intensely emotional a word is—regardless of whether it’s positive or negative.
By analyzing user-generated reviews of movies, books, and restaurants, they found that star ratings alone did not consistently predict a product’s success. But the emotionality of the written text was a more reliable gauge.
I took my observations further by posting two new Google reviews for local businesses:
Then, I compared both to a review I’d posted a year ago to see which got more engagement.
In the short time the reviews have been live, the one with stronger emotional language has already shown a trend toward higher engagement (views and likes), aligning with the Sephora findings. While further data might be needed for firm conclusions, it appears people gravitate to passionate, relatable feedback over simple facts.
For consumers, these findings offer a practical way to navigate review overload. When every product has 4 or 5 stars, look at the words, not just the rating. Are reviewers saying “I liked it” or are they gushing with “I absolutely loved it—this changed my life!”? That level of emotion hints at genuine passion and a stronger predictor of quality (or dissatisfaction, if the language is extremely negative).
For businesses that encourage customers to post reviews—perhaps by offering rewards—the research highlights a possible downside. Incentivizing people to write positive, persuasive reviews might unintentionally push them to use more emotional language than is ideal for certain categories. If the product is a highly functional, technical item (like a coffee grinder or a toaster), readers might want to know more about its rational pros and cons rather than see it described as “amazing.”
“You might actually be less persuaded by the message if it focuses too heavily on emotion,” Rucker says.
Companies also need to consider which influencers or bloggers they work with. A blogger known for emotive language could more effectively shape others’ opinions—and potentially predict which products have staying power.
Human decision-making and emotional motivations vary by category
Even when a review is positive, a lack of emotional language can signal lukewarm enthusiasm. A brand manager might see mostly favorable ratings—three or four stars—but if customers say only “good” or “nice,” that might indicate an absence of genuine excitement. Knowing why people aren’t raving can be an opportunity for a business to improve.
At SHOPLINE - we’re using these findings to improve how reviews are displayed. Many store owners list reviews in chronological order or by star rating. Yet studies show that buyers often read only the top 10–15 displayed reviews before making a purchase decision.
We recently worked with one of our merchants who has over 3,000 customer reviews in their SHOPLINE online store. Rather than leaving the default sorting (chronologically or by raw star average), we applied a new system that filters top reviews by valence (positive/negative sentiment), extremity (how strongly positive or negative), emotionality (intensity of emotion), and certainty (how confident they sound).
Below is an illustrative table. The left side represents the typical “default” top reviews (often short, time-based), while the right side uses advanced sorting to bring the most enthusiastic and confident feedback to the front:
By surfacing reviews that exude both strong positive emotion and high certainty, the merchant’s prospective buyers see messages that are more confident, persuasive, and authentic. This approach:
By incorporating measures of emotionality and certainty, online stores can transform generic positivity into valuable insights. At SHOPLINE, we provide research-backed insights and tools that help merchants surface the most telling reviews - whether they convey genuine delight or honest disappointment. This allows shoppers to see not just a product’s star rating but also how it made other customers feel and how confident they are about it.
This shift isn’t just about finding “the right” product; it’s about enhancing the overall shopping experience. When readers see authentic, emotion-rich feedback, they feel a stronger connection to both the product and the brand, leading to deeper trust and higher satisfaction. Over time, customers learn to rely on these more transparent and genuine reviews, making more informed decisions and forging a closer bond with the merchant.
Ultimately, if you rely only on the number of stars, you might miss the signals that really matter - where shoppers share personal stories, express genuine passion, or speak with certainty. By spotlighting enthusiastic and heartfelt feedback, merchants can encourage trust, guide new visitors through their purchase journey, and ultimately foster lasting loyalty. After all, a standard five-star rating may be good, but an emotionally charged review that conveys a reviewer’s excitement and certainty is often what truly clinches the sale.
Reference:
Rocklage, Matthew & He, Sharlene & Rucker, Derek & Nordgren, Loran. (2023). Beyond Sentiment: The Value and Measurement of Consumer Certainty in Language. 002224372211348. 10.1177/00222437221134802.
Rocklage, Matthew D et al. “Persuasion, Emotion, and Language: The Intent to Persuade Transforms Language via Emotionality.” Psychological science vol. 29,5 (2018): 749-760. doi:10.1177/0956797617744797
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