You know what emotional intelligence is — having a feel for what’s right, as distinct from a razor-sharp intellect. Fashion intelligence (FI) is the style equivalent: it’s a flair for putting together clothes that exists independent of money or looks, or even trying.

FI has nothing to do with real intelligence, which is why the Olsen twins look great, despite being college dropouts and why, even though Kirsty Wark has a brain the size of the Highlands, she looks as if she shops in Burton.

Looking good is an achievable goal for most women. With a bit of care, attention and maybe a great shoe, even a plain Jane can achieve a medium-FI score. Desperate Housewife Felicity Huffman, for instance, scrubs up nicely for her red-carpet appearances. But folk with high fashion intelligence are in a different league. They don’t just look okay. They look fabulous, almost all the time.

At its root, FI is about understanding fashion — being able to see beyond trends to the clothes that count, then putting them together in an original way. Having high FI doesn’t mean letting your stylist do all your thinking for you (we mean you, Mischa Barton). Nor does it mean wearing all your free gifts at once (hands up, Sienna, you’ve been rumbled). And just because you’ve got a great body, that doesn’t mean you can wear whatever you like. Madonna is guilty of this. Her recent outing in a satin disco tracksuit, tucked into spike-heeled boots and accompanied with stiff hair flicks, was more why-con than icon.

But one bad outfit is not the end of the world. Whereas your IQ remains pretty static, you can make vast improvements to your FI. Look at Nicole Richie. A year ago, she was an also-ran to Paris Hilton; now she’s starring in the latset Jimmy Choo ads and is a key LA trendsetter, complete with big shades, tiny body and fashionably baggy clothes. Coleen McLoughlin is another woman whose FI score is steadily improving. Her preference for rabbit-trimmed Mukluk boots and Juicy tracksuits is fading; now you are just as likely to see her in a vintage cocktail frock or a sleek Chloé number.

On the other hand, it is just as easy to slide down the FI scale as it is to clamber up it. Take Britney Spears (and give her a bath, please!). Once a frisky popette, now she’s bra-less and unkempt, with a junk-food complexion. Sienna Miller has also been haemorrhaging FI recently. The former queen of boho chic has seen her signature look consigned to trend oblivion, but still hasn’t found a convincing replacement for the gilets, peasant skirts and Ugg boots she wore with such pride only a year ago. The shapeless tent dress Miller chose for the Oscars was just the latest in a line of random outfits, and made us all wonder if Miller ever really had style.

Real FI is also a kind of physical gift. People with high fashion intelligence have a knack for wearing clothes. They hang right on them, crease in the right way; if they roll up a sleeve, undo a button or add a belt, some chemical reaction takes place and you have perfect rightness. It’s the reason Sofia Coppola wears Marc Jacobs better than anyone else. It’s also the reason designers with radically different styles will do almost anything to get Kate Moss fronting their campaigns. Forget her face, they are paying for the FI factor: the way she’ll twist a collar, knot the front of a shirt, make the clothes work for her, conjure the magic that gets us reaching for our chequebooks, regardless of what’s on sale.

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