Supermarkets are hotbeds of attempted seduction and rejection - mostly rejection. There are 30,000 products vying for attention in the aisles of a large outlet but only about 30 will be selected on an average shopping expedition, according to research from the British supermarket chain Tesco. What's more, shoppers commonly make product choices in less than three seconds.

Need, price and habit play significant roles in determining which products will comprise the 30 and which tens of thousands will be left languishing on the shelves. But the power of appearances shouldn't be underestimated.

In the 1940s Louis Cheskin, a US psychologist and the marketing mind behind the Marlboro cigarette man, coined the term "sensation transference" to describe the way people tend to fuse, unconsciously, the impressions made by a product's packaging with the product itself. You can blame him, in part, for the success of margarine in the US. Margarine was a fairly marginal product in North America after World War II, until Cheskin changed a brand of it from white to yellow (looks like butter), put it in foil (which was seen as a high-quality packaging material back then) and added an image of a crown to the package (denoting cachet). Imperial brand margarine became a tasty, desirable product.

Cheskin also discovered American shoppers are attracted to circles over triangles on packaging. Why, however, remains a tantalising mystery.

Green & Black's organic chocolate is a more recent example of the power of packaging. It hit the market in Britain in 1991 and its "organic credentials and high cocoa content earned it instant niche appeal" - but it managed to capture only about 1 per cent of the chocolate market, writes David Taylor, the author of several treatises on branding and the founding partner of Brandgym. "Green & Black's was sold mainly in specialist stores and when it was in supermarkets, it was stuck in the organic section."

A decade later, branding and design company Pearlfisher was employed to give Green & Black's a makeover. The updated packaging de-emphasised the organic message and instead promoted ideas of luxury and intense flavour. This was achieved in large part through tasty-looking wrapping in shades of brown and cream - created specially for the brand by the colour authority Pantone - and overlaid with prestigious-looking gold and brown typography. Nothing about the chocolate itself changed but it escaped the health-food aisle and sales went mad (increasing by 700 per cent, according to Pearlfisher). The brand was snapped up by Cadbury Schweppes in 2006 for an undisclosed but undoubtedly large sum.