And we know exactly how much it helps; since 1946 this category has taken an astonishing 68 nominations for Best Actor/Actress or Best Supporting Actor/Actress, winning 24 of them. This year it's represented by Emily Watson (wheelchair-bound in Hilary And Jackie), and Billy Bob Thornton (who experiences learning difficulties in A Simple Plan).
That post-war time-frame is no accident; the 1946 winner was Harold Russell, a Canadian paratroop sergeant who lost both hands in a non-combat mission during the Second World War. Director William Wyler cast him as a handicapped naval vet in The Best Years Of Our Lives, and so affecting was his performance that the Academy not only awarded him a special statuette for "bringing hope and courage to his fellow veterans", but threw in Best Supporting Actor to boot.
"I didn't figure they'd give it to the gimp," exclaimed Columbia Pictures boss, Harry Cohn. But the lesson wasn't lost: he and his fellow studio heads were soon having "gimp" roles hand-crafted for their stars. Two years later, the Best Actress hopefuls included Olivia de Havilland as a steaming paranoid schizophrenic in The Snake Pit; Barbara Stanwyck as a bedridden invalid in Sorry, Wrong Number; and Jane Wyman, the eventual winner for her deaf mute in Johnny Belinda.
Certain actors have cornered the market in Oscar-friendly unfortunates. In 1969, Dustin Hoffman was nominated Best Actor for the crippled Ratso Rizzo in Midnight Cowboy; almost 20 years later, he finally scooped the statuette for his meticulous autistic savant in Rain Man.
Jack Nicholson's rich array of crazies has garnered him two wins: for the lobotomised mental patient in One Flew Over The Cuckoo's Nest and the obsessive-compulsive writer in As Good As It Gets. ("I guess this proves there are as many nuts in the Academy as anywhere else," he delicately observed when picking up Best Actor for the former.) And Billy Bob Thornton's Simple Plan performance is his second simpleton nomination; his first was for 1996's Sling Blade. The blood chills at the thought that he might keep trying every couple of years until he gets it right.
A better bet might be a fresh onslaught on an old Academy favourite among history's luckless: Cyrano de Bergerac (Jose Ferrer, Best Actor, 1950; Gerard Depardieu, Best Actor nominee, 1990), The Elephant Man (John Hurt, Best Actor nominee, 1980), or Vincent Van Gogh (Kirk Douglas, Best Actor nominee for Lust For Life, 1956).
But there are unwritten rules about getting an Academy acknowledgement when playing the disabled. Most important, there has to be a certain amount of optimism to go along with the pain: ie I-may-only-be-a-head-on-a-skateboard- but-I'll-get-that-Paralympic-gold-medal-if-it-kills- -me. This attitude chimes with the Academy's other favourite class of nominee: Those Displaying Heartwarming Courage In The Face Of Terminal Disease. This year's representative of the genre is Meryl Streep, succumbing to cancer in One True Thing.
It also helps if your film errs on the Terribly Worthy side. Anything tag-lined "An hilariously irreverent look at multi-impairment!" is not likely to warm the Academy's cockles. But the most important rule of all is that the disabled have no place in a disabled movie. These, after all, are big, starry, grandstanding roles, tailor-made for Hollywood's most beautiful people to display their range and, (by the by of course) get a potentially huge career-booster.
Some carry it off triumphantly - Daniel Day Lewis, Best Actor in 1989 for My Left Foot (perhaps the ultimate disability role), or Leonardo DiCaprio in What's Eating Gilbert Grape. Some crash into the buffers - Brad Pitt, Best Actor nominee in 1995 for his wearying repertoire of tics in 12 Monkeys, or child-woman Jodie Foster shrieking her way to a Best Actress nomination in 1994 in Nell.
When a disabled actor does break through, their careers tend to be short- lived: Marlee Matlin, who didn't have to pretend to be deaf to win Best Actress for Children Of A Lesser God in 1986, has disappeared without trace.
Campaigners for the disabled find it all a little irksome. "It's an uphill struggle to get disabled actors into mainstream films," says Marilyn Graves, arts editor of Disability Times magazine. "I don't blame able-bodied actors for taking the roles. But sometimes, as in the case of Forrest Gump, they seem to be saying that it's OK to be mentally retarded as long as you're cuddly with it. It's that kind of simplification and glamourisation that I find offensive. The film-makers sometimes claim they're raising awareness of a particular condition, but it's hard to think of any practical benefits that accrued to those suffering from autism as a result of, say, Dustin Hoffman's performance in Rain Man. I'm not saying that only disabled people should play disabled parts; it's obviously not possible in some cases. I'd just like to see them given a fair crack of the whip. After all, white actors don't black up to play black roles any more, and to me it amounts to the same thing."
It's a point echoed by Martin Brown of British Equity, which has 180 disabled actors on its books. "Equity policy is, if there's a disabled role to fill, the genuinely disabled should be given priority at auditions. There'll be no more disabled stars winning Oscars as long as they're repeatedly passed over for the jobs that they seem uniquely qualified to do."
"Pacino or Hoffman playing blind or autistic roles is a joke," says Charlie Higson, Fast Show star and presenter of Channel 4's film show Kiss Kiss Bang Bang. "We did a Fast Show sketch about it, featuring the Cute Disabled Man, because if you play disabled in movies you're not allowed to frighten the horses - you're there to suffer nobly and stimulate the finer feelings of the able-bodied. They're easy options for actors: it's harder to play an ordinary person and make it convincing than to do one of those raving and drooling parts. But the movies are about making money, so they'll continue to cast stars in these parts and the Academy will doubtless continue to honour them."
Indeed, garlanded gimp roles will always be with us; upcoming examples include The Theory Of Flight, featuring a woman with motor neurone disease; At First Sight (a blind man); and Molly (an autistic woman).
The stars are, respectively, Helena Bonham Carter, Val Kilmer and Elizabeth Shue. They might as well pick their Oscar frocks and start rehearsing those tearful acceptance speeches right now.
AND THE WINNING DISABILITY IS...
! Psychotics of one sort or another (16 nominations, including Gloria Swanson in Sunset Boulevard, Geoffrey Rush in Shine and Edward Norton in Primal Fear)
! Mental retardation (eight nominations, including Peter Sellers in Being There, Leonardo DiCaprio in What's Eating Gilbert Grape and Tom Hanks in Forrest Gump
! Blind people (seven nominations, including Audrey Hepburn in Wait Until Dark, John Malkovich in Places In The Heart and Al Pacino in Scent Of A Woman)
! Paraplegics (five nominations, including Jon Voight in Coming Home, Tom Cruise in Born On The Fourth of July and Gary Sinise in Forrest Gump)
! Mutes (three nominations, the most recent of which was Holly Hunter in The Piano)