Image caption Clockwise from left: Caligula, Idi Amin, Saparmurat Niyazov, Francois Duvalier and Kim Jong-il

Sacha Baron Cohen's latest comedy, The Dictator, features the antics of a fictional leader from North Africa. Admiral General Aladeen is an extreme representation, but why do real autocrats so often do strange things?

Cohen's character lives in luxury in Wadiya, surrounded by an army of female bodyguards.

The film, on worldwide release this week, is about his travels to the US to address the United Nations.

The figure is clearly inspired by leaders like Muammar Gaddafi, killed after being ousted from power in Libya last year.

"Dictators can become self-delusional in a way, and think 'whatever I do is ok'," says Fred Coolidge, a psychology professor at the University of Colorado, who has profiled Kim Jong-il, Saddam Hussein and Adolf Hitler.

He believes that many such leaders may share a combination of personality disorder traits such as narcissism, paranoia and sadism.

A study of some of history's most infamous autocrats sheds some light on what drives their strange behaviour.

Testing power - Emperor Caligula (AD 12 - 41)

It's a bit like if you made a teenager prime minister without any previous training Dr Benet Salway, University College London BBC History - Caligula

Roman Emperor Caligula was one of the earliest autocrats, known for his short temper and erratic behaviour.

"He ordered boats to be rounded up and put in a line across the Bay of Naples, so he could walk across them from one town to another," says Dr Benet Salway, a senior lecturer in history at University College London (UCL).

He also loved race horses, and was said to have lavished his favourite horse with a house, a troop of slaves, and wine in golden goblets.

Caligula's erratic behaviour, which also included ordering troops to gather sea shells during a campaign against Britain, led many to question his sanity.

However, Prof Peter Wiseman, a classicist from the University of Exeter, believes that Caligula "knew exactly what he was doing. He simply exploited to the full the possibilities for absolute power and self-indulgence".

Is power or personality to blame? A confluence of genes creates personality disorders like narcissism, paranoia and anti-socialism, says Prof Coolidge, but the environment encourages them, especially if they're born into power. "That push from the hereditary is as strong or stronger than the environment. However, whilst these are genetic predispositions, the environment helps to promote these natural occurring predispositions by many times." A feature of a narcissist is that they are power-orientated, attracted to powerful positions, he says. "If you want to be powerful, and if you have that drive, you may be led to be a dictator. There are hardly any reluctant ones. And once they're in power they're hard to dislodge. These traits manage to keep them in power - for example, if you're hypersensitive to threats and plots then you can effectively eliminate your competition." Many anti-socials are highly charismatic, and can charm their way to power, sometimes ruthlessly.

Similarly, Dr Salway believes Caligula's young age - he was 24 when he assumed power - and lack of experience, may explain his actions.

"It's easy to see how someone given absolute power, without any preparation, could let it go to his head… it's a bit like if you made a teenager prime minister, without giving them any previous training.

He may have also been testing the limits of his power, he says. "Every time people pandered to his demands, it probably fuelled him, and made him believe that he was all powerful."

But not everything that is said about the eccentricities of leaders should be believed. The story that Caligula made his horse a consul - one of the highest official positions in Rome - is thought to be a myth.

"No horse ever became a consul," says Dr Salway. Historical sources do say that Caligula promised to do this, he adds.

"But it sounds like a joke, borne of frustration with members of the senate, who Caligula had a bad relationship with."

Superstitious - Francois Duvalier (1907-1971)

Many autocrats have a tendency for paranoia which is magnified by their environment, says Prof Coolidge.

"Their traits can help keep them in power - for example, if you are hypersensitive to threats and plots then you can effectively eliminate your [real or imagined] competition."

Haiti's former president, Francois "Papa Doc" Duvalier, demonstrated plenty of paranoia during his 14 years in power.

Image caption Francois Duvalier claimed to practise voodoo

A voodoo physician, he was extremely superstitious, and believed that he was guarded by voodoo spirits on the 22nd of each month. In later years, he only left the presidential palace on the 22nd of each month.

He claimed to have placed a voodoo curse on US President John F Kennedy, and said Kennedy's assassination on 22 November 1963 was caused by his powers.

He had a personal guard called the Tonton Macoutes - Haitian slang for "bogeymen" - and banned civic organisations he thought were a threat to his rule - including the Boy Scouts.

He was also reported to have ordered the killing of all the black dogs in Haiti.

He survived at least six assassination attempts, but died after a period of illness in 1971.

Obsessed - Idi Amin (1920s-2003)

Image caption Idi Amin awarded himself countless medals and honours

Idi Amin, who ruled Uganda in the 70s, enjoyed giving himself titles, including "Conqueror of the British Empire" and, most famously, "King of Scotland". He also promoted himself to field marshal and awarded himself the Victoria Cross and Military Cross.

He was obsessed with showing himself as equal or superior to Queen Elizabeth II, and said that he, not the Queen, should be head of the Commonwealth.

There were reports that he kept the severed heads of political opponents in his refrigerator. While this has not been proven, he once said to an adviser before dinner: "I want your heart. I want to eat your children."

He had five wives, fathered dozens of children, and insisted on being called "Big Daddy".

Cult of personality - Saparmurat Niyazov (1940-2006)

Turkmenistan's president-for-life Saparmurat Niyazov established a cult of personality that could easily have rivalled that of Cohen's "dictator". He had a 15m (50ft) gold-plated statue of himself built and it revolved so it always faced the sun.

Whilst the majority of people in Turkmenistan lived in poverty, he had an ice palace built in the capital, and ordered the construction of a lake in the middle of the desert.

He also named cities, a theme park, the month of January, and even a meteorite after himself.

Image caption Portraits and statues of Niyazov were commonly seen

Despite his extravagant projects, the leader may be best known for the bizarre laws he established. After giving up smoking in 1997, he ordered all his ministers to do the same. He also banned ballet, opera, and beards and long hair from men.

Like Saddam Hussein, he wrote a book. Rukhnama was a collection of his thoughts on Turkmen identity and history, which became required reading in the curriculum of schools and universities. Bizarrely, citizens even had to pass a test on the book before being granted a driving licence.

Like Caligula, he was also fond of horses, and opened a $20m (£12m) leisure centre for horses, complete with swimming pool, air conditioning and medical facilities.

Niyazov died in 2006 and the gold statue was moved in 2010.

His successor Kurbanguly Berdymukhamedov established an annual horse beauty contest in 2011 that included awards for the best carpet featuring a horse, and the best "holiday attire" for a horse.

Lobster lover - Kim Jong-il (1942-2011)

Image caption Critics said Kim kept a bouffant hairstyle to make him look taller

Few modern autocrats have been as shrouded in controversy as the late North Korean dictator Kim Jong-il.

Styling himself as the "Dear Father" of Korea, he used North Korea's state-controlled media to perpetuate myths about his power and status.

The stories ranged from the mythical to the everyday. According to official accounts, a double rainbow and a bright star appeared in the sky when he was born - and, when he died, a giant lake of ice cracked in half.

State media also said that, the first time he bowled, Kim Jong-il scored a perfect 300, and in his first round of golf he had five holes-in-one for a 38-under par round.

"[Dictators] don't mind spending millions of dollars promoting the cult of their own personality… [and] have little empathy for anyone else, seeing only their own needs," says Prof Coolidge.

This certainly seems to be reflected in the luxurious lifestyle - like Niyazov - that Kim Jong-il enjoyed, while hundreds of thousands of North Koreans died in famine.

Reports say that, while travelling by train across Russia, Kim - who hated flying - had live lobsters air-lifted to the train each day.

His love of movies also led him to order the abduction of a South Korean film director and his actress wife, who were ordered to make films for him until they managed to escape.