The supermarket camera that looks inside your head

If You feel bewildered when your supermarket moves things round on the shelves, spare a thought for it and the firms that produce the goods. They are just as puzzled by your actions.

Much effort is devoted to investigating shopping patterns. Traditionally, this has been done by interviews. But consumers are unreliable and the reasons they give for buying things are not necessarily accurate.

Now, Siebert Head, the design consultants, and ID Magasin, the retail researchers, claim to have developed a more sophisticated and objective way of finding out how customers think. The technique, called PackTrack, uses an infra-red eye-tracking device to record a video image of what the consumer sees on the shelf. This record is overlaid with a zigzagging line that shows the instantaneous focus of the consumer's attention.

Interpretation of the videotape provides a precise indication of what it is in what the consumer sees that leads to the decision to buy something. Siebert Head is a long-established packaging design firm and ID Magasin advises shops on lighting levels, and store and shelf layout. They have combined their expertise to narrow the kind of monitoring often used in a store-wide context down to individual shelves and individual packs. The process reveals the significant elements of pack design and stacking.

The companies claim that PackTrack is the only method of providing an objective evaluation of brand performance on the shelf. "Shopping is very much a non-rational process," says Siemon Scamell-Katz, the managing director of ID Magasin. "So consumers post-rationalise."

The eye-tracking process was originally employed in the aerospace industry in aircraft cockpit design, and later adopted for other ergonomic studies. The department of vision sciences at Aston University has used it to investigate road usage and the ideal positioning of road signs, for example. Aston is one of several university groups to have contributed to two years of studies that preceded the launch of PackTrack. Retailers such as Asda and Superdrug have also been involved.

In a typical operation, up to 200 shoppers are covertly monitored by remote video cameras. From these videotapes it is possible to extract a certain amount of solid data - for example, the time from aisle to a given shelf location, or the time spent in front of a shelf before the consumer plucks an item from it. The proportions of product selected and retained, or selected and replaced, are also measured. "We can contextualise these measures to see if it is taking a consumer too long to interact," says Mr Scamell-Katz.

What is not revealed is why consumers do what they do. So afterwards they are invited for interview. Typically, half of the 200 tell the researchers where they can put their video. The others offer explanations for their actions - why they chose certain brands and left others, why they hesitated here or were attracted there.

Two dozen or so are then invited to perform a second shopping exercise, this time wearing the eye-tracking headset. This time the videotapes show the scope of each consumer's vision and the focus of attention at any instant. They are slowed down by a factor of 100 in order to study the pattern of eye movement and points of fixation.

This analysis reveals the relative importance of elements of individual pack design, such as colour, shape, product name, brand and corporate logo, illustration and photography. It also shows the eye as it cuts away to prices on the shelves and comparable products.

In the case of a frozen food client, for example, Siebert Head and ID Magasin were able to establish that the illustration was more significant than the branding. Likewise, the grouse is important for consumer recognition of Famous Grouse whisky, but the name counts for more in the case of Bell's. The eye-tracking process also enables marketers to understand how a distinctive colour or an attractive picture can be used to draw the consumer's eye to the product name or other important information.

Results must be interpreted with care. An observation of many fixations is an indication not of interest but of confusion. Some consumers fixate in disbelief on a product if its packaging is strikingly ugly, for example, not because they are considering a purchase. For such reasons, debriefing interviews remain important. Items showing high levels of fixations are not always the ones that are recalled in interviews.

Siebert Head and ID Magasin report great interest, especially from large corporations with blue-chip brands, such as Procter & Gamble. "They would like to gain live information from consumers while they are shopping," says Satkar Gidda, the marketing director at Siebert Head. Some clients may be tempted to use this technique as a prescription for the ideal pack design, but that would be to miss the point, says Mr Gidda. "The intention is to enable clients to understand how packaging works in the market, not to give a design brief."

PackTrack might tell you, for example, that three out of seven elements of a pack design are crucial to its appeal and that any redesign must be treated with care.