“This is the hotel of your dreams.” “This oven will explode when you turn it on.” “This restaurant has the best, most tender steak I ever ate.” That’s the kind of commentary you can find from consumers who review a range of products and services on Web sites, but how do you know whether you can trust them? They may appear to be honest critics, but many are tricksters intentionally misleading you.

Some sparkling reviews actually are posted by people who work for the businesses that are being reviewed…by marketing companies hired by those businesses…or by consumers who have been bribed with free merchandise.

Negative reviews are not always legitimate either. Some are posted by competing businesses…by disgruntled former employees…and by others who have axes to grind.

This is troubling because about 80% of Internet shoppers change their minds about purchases based on online reviews from other consumers, according to a 2011 survey by the market analysis firm Cone Communications.

We asked Cornell associate professor Jeffrey Hancock, PhD, who led a study of online reviews, how we can distinguish honest ones from phony ones…

Trust reviews that feature numerous references to space, size and distance. When we use a product or a service such as a hotel or restaurant, our minds make note of things such as size and distance. When we later describe the experience, these spatial aspects inevitably come out.

Examples: We might note that a hotel room seemed too small to fit a suitcase…that a popular restaurant was just a block east of our hotel…or that a product was larger than we expected.

In contrast, our team’s research suggests that people tend to make significantly fewer references to space, size and distance when they fabricate reviews. Their descriptions of hotels or restaurants generally say little about where they are or how to reach them…and their descriptions of products generally say little about the size of the products.

Helpful: It’s tricky to judge just how many spatial references are sufficient to suggest an honest review, so our team created a free online tool to help. Copy and paste a review into Review Skeptic (www.ReviewSkeptic.com), and it will tell you whether it’s truthful or deceptive with about 90% accuracy, based on a test run conducted on 800 reviews of Chicago hotels that had been validated as real or fake. Review Skeptic currently is designed to vet only hotel reviews, but we expect to expand the site over the course of 2012 to include evaluations of online product reviews and doctor reviews.

Trust reviews of the reviews. Web sites that feature user reviews sometimes let other consumers rate the usefulness of each posted review.

Example: On Amazon.com, reviews often are preceded by a statistic reporting how many other shoppers “found the following review helpful.”

Reviews that receive high scores from other users generally are honest. A fake review might be convincing enough to fool those who are unfamiliar with the product in question, but few fake reviews can overcome the collective wisdom of all shoppers on a Web site.

True, someone who writes a fake review also could fake a good score for that review by logging onto the site many times under different names and reporting the review helpful—but that would be very time-consuming, so it doesn’t happen often.

Seek confirmation from other sites. Enter the name of the product or service that you’re considering and the word “reviews” into a search engine to find other sites that offer user reviews or professionally written reviews of it. Be suspicious if different review sites offer substantially different opinions. A fake reviewer might have targeted one site but not another.

Beware of reviews offering strong opinions but few specifics. Reviews that provide little detail beyond over-the-top adjectives extolling or panning a product or service often are fake. And even if these reviews are honest, they’re not very useful—without specifics, there’s no way to know whether the reason for the strong opinion is something that is important to you.

Trust reviews from verified customers. Some Web sites that feature online user reviews specify which of those reviews come from shoppers who actually purchased the product or used the service through the Web site. Reviews that come from verified customers are very likely to be honest.

Example: On Amazon.com, reviews labeled “Amazon Verified Purchase” are written by people who bought the item from Amazon.com.

Some hotel review Web sites, including www.Hotels.com and www.Orbitz.com, do not allow users to post reviews unless they have booked a room at the hotel through the site, greatly decreasing the odds of fake reviews. Other sites, including www.TripAdvisor.com, let anyone post a review, making fakes more likely.

Read the negative reviews even if they’re outnumbered. A product or service that receives mostly very positive reviews still might have a few very negative reviews. True, those harsh reviews might be written by cranks—but they also might be the only honest reviews. Someone might be trying to bury the honest negative reviews under a flood of fake raves.

If the bad reviews point to similar, specific and significant problems, there could be cause for concern. Maybe the raves are fakes or maybe there’s a serious problem that only crops up in some cases. Either way, proceed with caution.

Example: An elliptical trainer received great user reviews—except for a handful of negative reviews, each of which mentioned that a particular metal bar on the device snapped, a sign of a serious flaw.

Trust the product’s or service’s overall score if there are at least 50 or so reviews of it on the site. When there are a large number of reviews, it’s hard for fakers to skew the score. It would take too much time and effort to substantially alter it.

Do not be convinced by “balanced” reviews. There’s a widespread belief that online user reviews must be honest if they make any attempt to be balanced—a score of four stars rather than five, perhaps, or a mention of some small feature that they say could have been better but was not terrible. Unfortunately, savvy fake reviewers have figured out that shoppers trust balanced reviews, and some now intentionally include a touch of balance to add credibility.

Be particularly leery of reviews of doctors. Our preliminary research into online reviews of medical providers suggests that the deception rate can be high, likely in part because medical provider review Web sites do not yet attract the heavy volume of legitimate reviews that product, hotel and restaurant review sites often do, making it easier for fake reviews to skew the results.

The sites that provide doctor reviews—most notably www.RateMDs.com—are aware of this problem and are trying to correct it. But for the time being, I would not recommend selecting a health-care provider based solely on online reviews. Instead, obtain recommendations from your other health-care providers or from people you know and trust.

Be suspicious of rave reviews from “top reviewers.” Some sites identify certain reviews as coming from elite reviewers who are particularly active on the site. Example: On Amazon.com, some reviewers are described as “Top 500” or “Top 1,000” reviewers.

Consumers tend to assume that reviews from these elite reviewers must be particularly trustworthy. But a recent survey of 166 of Amazon’s top 1,000 reviewers (whose names and/or e-mail addresses often are publicly available by Cornell professor of science and technology studies Trevor Pinch, PhD, suggests that these top reviewers often are not as independent as they seem.

It turns out that product marketers know that opinions from top reviewers carry a lot of weight, so they shower the top reviewers with free merchandise in hopes of getting these products reviewed. The top reviewers understand that the free stuff will stop arriving if they are critical in their reviews, so many of them write overwhelmingly or exclusively positive reviews.

Before trusting a review written by a “top reviewer,” scan other reviews written by this person. Make sure that there’s a full range of positive, neutral and negative scores—not all raves. On Amazon.com, this is done by clicking “See all my reviews.”

Helpful: Also be wary of reviews labeled “Amazon Vine.” This means that the reviewer received the product for free from Amazon.com.