The observational research has "given us a much better understanding about what occurs in people's showers," says Jack Suvak, director of marketing research for Ohio-based Moen.
And it reinforces one principle that many observational researchers agree on: They can delve into very private areas as long as the consumer has the choice up front not to participate. How obvious that choice should be gets a little tricky.
In downtown Minneapolis, a retail-brand agency called Fame runs an elegant store that sells an eclectic mix of gifts and housewares from $1.99 greeting cards to $15,000 antique furniture.
But it's really a laboratory for retailers. Wired with microphones and cameras, the store carries products that manufacturers want to test on shoppers.
Earlier this month, Fame displayed a variety of soaps with unusual ingredients. It found that while eggplant soap might attract the curious, shoppers generally gravitated to more familiar scents. The cameras also collect other clues.
"We can test a customer's interest in a product by how often they pick it up, how they look at it," says Jeri Quest, Fame's executive vice president of strategic development.
Often, a Fame researcher will approach a customer to ask for additional information. So far, the combination of overt and covert research has elicited no complaints.
"Customers understand what's happening, and they have a choice" to shop or not shop at the store, Ms. Quest says. Just outside the store, a blinking sign alerts would-be shoppers when a test is under way.
Of course, observational researchers also tape customers without their knowledge a practice researchers defend as long as customers remain anonymous.