San Francisco (Business 2.0) - Presented with a magazine ad touting GM's quality improvements, the middle-age man on the videotape checks off a box on his market survey card indicating that he feels "reassured."

But Dan Hill, who has been watching the video again and again in slow motion, observes a completely different reaction. "There!" Hill says, pointing at the screen as the man's eyebrows drop and his mouth tightens against his teeth. "That's what we call a 'lip press.' I see anger, disgust, maybe some micro-contempt. This man is not buying the message."

Hill is president of Sensory Logic, a 12-person consulting firm based in St. Paul, Minn., that's devoted to the premise that what people tell market researchers is at best only part of what they're really feeling -- and at worst simply false.

"People lie to appear polite or intelligent all the time in real life," Hill says. "Why wouldn't they do it in a focus group?"

To get at the truth, Hill detects emotions by observing facial expressions. If that sounds like so much New Age hocus-pocus, consider that some of America's most innovative marketers, including Target, Nextel, and Eli Lilly, have hired Hill to read the faces -- and minds -- of their customers.

Says General Motors advertising research manager Alka Baijal, "His techniques let us get directly to emotional response."

Ever since Columbia University sociologist Robert Merton performed what is considered the forerunner of the modern focus group -- a 1941 interview of radio listeners regarding their views on the U.S. government's morale-boosting shows -- market researchers have suspected that subjects deny, exaggerate, and otherwise misreport their own emotions.

Merton himself, in his 1956 book The Focused Interview, warned that societal norms might cause interviewees to "censor their self-reports, denying (sometimes even to themselves) the stirrings of sentiment."

He imagined that marketers might one day invent an "introspectometer," but noted that "since no such device exists, the nearest equivalent available is to have each subject act as his own introspectometer."

If Hill and his high-profile customers are to be believed, something akin to Merton's device has finally arrived.

Hill, who quit his PR job at New Jersey utility PSE&G seven years ago to found Sensory Logic, discovered it while scanning academic libraries for scientific ways to measure emotional response to advertising.

The tool he stumbled upon was the Facial Action Coding System (FACS), developed in the 1970s by Paul Ekman, a University of California at San Francisco psychologist.

Ekman and a colleague identified the 43 muscle movements responsible for all human facial expression.

They spent seven years categorizing roughly 3,000 combinations of such movements and the emotions they convey -- the "eyelid tightener" expresses anger, for instance, and the "nasolabial fold deepener" manifests sadness. The system has proven to be highly accurate; the FBI and CIA reportedly use Ekman's methods to determine the emotions of suspects during interrogations.

Hill modified the technique for market research.

To measure initial gut reactions to a commercial or ad, he first attaches electrodes to the side of a subject's mouth (monitoring the zygomatic muscle, for smiles), above the eyebrow (corrugator muscle, for frowns), and on two fingers (for sweat).

He says the facial muscle movements reflect appeal, while perspiration translates into what he calls "impact" -- emotional power.

Last summer Hill wired up 40 subjects recruited from a Pittsburgh mall and showed them a Nationwide Insurance TV commercial called "Smashworld," which depicted a parallel universe with no insurance -- and streets full of dented cars.

When onscreen Nationwide agents saved the day (by processing claims), appeal and impact scores soared.

But when two men had an accident in the final scene -- added for comic relief by Nationwide's ad agency -- appeal tanked.

"With Dan's methodology, you really see where audience attitude goes south," says Nationwide market researcher Michelle Tufford. She went instead with a spot that had a happier ending.

After Hill takes initial readings, he ditches the electrodes and he videotapes an interview with each subject.

Later his FACS-trained team reviews the video, second by second, cataloging emotions.

Replaying the tape of a young woman who says she's "bored" by one version of Nationwide's logo, Hill points out that her expressions say much more. "Her eyebrows come together in a triangle," he says. "And see that upside-down smile? She's approaching what we call a 'super-sneer.'"

She wasn't bored by the logo, he says -- she despised it. Nationwide's Tufford says the logo at the end of her company's TV ads was chosen almost entirely based on Hill's data.

Even some of Hill's happy customers say face reading has limitations.

For one thing, not everyone believes that pitches have to aim for the heart. "A lot of the advertising we do is a more rational sell," GM's Baijal says, "so emotional research doesn't apply. And when it does, this data is just one input among many."

Which leaves some focus group veterans wondering why Hill's methods are considered a specialty. Robert Kahle, who's been running focus groups for automakers for 20 years, says analyzing nonverbal communication is "part and parcel of what a good moderator does."

Be that as it may, Hill is in demand -- and not just for ad-copy testing.

Texas Instruments, for instance, recently hired him to determine whether moviegoers really prefer traditional film projection to digital, as many dyed-in-the-wool Hollywood filmmakers claim.

TI, which makes semiconductors used in digital movie projectors, wanted hard evidence that would persuade studios to release films in digital format.

So Hill pasted electrodes on viewers at a theater in Plano, Texas. Wires dangling from their faces, some watched 10-minute digital clips of the animated feature Finding Nemo or the live-action X-Men sequel, X2, while others watched in analog.

As it happens, viewers registered more intense reactions to the digital version of Nemo. The results were less clear-cut for the digitized X2, but still encouraging.

"Frowns showed less intensity," says TI marketing communications manager Cheraina Dunn, "but smiles were above-normal."

The biggest smile, undoubtedly, was the one on Hill's face.