We present evidence that many product reviews at a private label retailer’s website are submitted by customers who have not purchased the product they are reviewing. We show that these reviews are significantly more negative than other reviews. Moreover, because the reviews are influential, the negative ratings reduce sales of these items.

Deception is generally considered a more cognitively complex process than merely stating the truth leading deceivers to use less complex language. The complexity of the language is often measured by the length of the words used.

Because it is often difficult for deceivers to create concrete details in their messages, they have a tendency to include details that are unrelated to the focus of the message. For example, in a study of deception in hotel reviews report that deceptive reviews are more likely to contain references to the reviewer’s family rather than details of the hotel being reviewed. Other indicators of deception reported in hotel reviews include using more exclamation points “!”

The results indicate strong evidence of deception in the reviews written without a prior transaction. Recall that the word count is one of the most commonly used linguistic cues used to detect deception. The word count for the reviews without prior transactions is approximately 40% higher than in the reviews with prior transactions. We also observe significant (p<0.01) differences on each of the other linguistic cues. We caution that these differences do not indicate that all of the reviews without prior transactions are deceptive. Instead we conclude that these reviews are more likely to contain linguistic cues that are consistent with deception, suggesting that at least some of these reviews are deceptive.

Amazon. The sample of 80 books had a total of 7,219 reviews, averaging 90.2 reviews per book. This included an average of 52.7 reviews tagged as an Amazon Verified Purchase and 37.6 that were not tagged. We report the average rating and the distribution of ratings for these two samples of reviews. We see that the low rating effect is replicated using these reviews from a separate retailer in a different category. The magnitude of the effect is similar to the findings reported before, with approximately twice as many ratings equal to 1 amongst the reviews without a verified Amazon transaction (9.38% versus 4.77%).

Why people write such stuff: The second explanation is in some respects the reverse of the upset customers explanation. It is possible that these customers are acting as “self-appointed brand managers”. They are loyal to the brand and want an avenue to provide feedback to the company about how to improve its products. They will even do so on products they have not purchased.

Third explanation is that reviewers are simply writing reviews to enhance their social status. This explanation is related to the more general question of why do customers ever write reviews with or without prior transactions? In an attempt to answer this more general question some researchers have argued that customers are motivated by self-enhancement. Self-enhancement is defined as a tendency to favor experiences that bolster self-image, and is recognized as one of our most important social motivations. Self-enhancement may explain why reviewers write reviews for items they have not purchased. However, it does not immediately explain why these reviews are more likely to be negative. One possibility is that customers believe that they will be more credible if they contribute some negative reviews.

Check at full at http://web.mit.edu/simester/Public/Papers/Deceptive_Reviews.pdf