Did you know that fleas can jump great heights? In fact, they can jump the equivalent height of a human jumping a house. If you have a dog that has ever had fleas, that fact shouldn't come as a great surprise. If you ever do catch a flea, here is a brilliant experiment to try with it.

If you put a flea in a jar and then put a piece of cardboard on top of it, despite being able to jump far higher than the top of the jar, once the flea bangs its head against the card a few times it will never again, in its whole life, jump higher than the height of the card on top of the jar. That way they are easy to control and you need never worry about them again. This is how they train the fleas in flea circuses.

What has this got to do with you and your beliefs, you may be asking. Bear with me.

Once you have got rid of their fleas, here's an experiment for dogs that is interesting to note. In the 1960s Dr Martin Seligman of the University of Pennsylvania noticed during an experiment involving some dogs that when they experienced any physical pain they just gave up and lay down, whimpering pain. He was fascinated by this and wanted to investigate further, so he carried out another stage to his investigations.

He put dogs into three groups, A, B and C. Dogs in group A were placed in a box and then given an electric shock. The dogs could stop the shock by pressing a bar with their nose and they learned to do this pretty quickly! Dogs in group B were placed in another box and were given a similar shock, but they had no way of stopping it. Finally, dogs in group C were placed in the box but were not given any shocks at all.

The next day, the same dogs were placed in a different box, which had a low barrier placed down the middle of it. One side of the box gave off an electric shock when the dogs were placed next to it but, by stepping over the low barrier to the other side of the box, they could escape the electric shock.

Guess what happened?

The dogs in group A (those that had been able to turn the shock off the day before) and group C (those that had not received any shocks) very quickly learned to step over the barrier and escape the pain of the electric shock. Group B dogs (the ones that couldn't control the shocks in the first part of the experiment) didn't even try to escape. Instead, they conceded immediately, lay down and whimpered. They believed that they had no control over events and gave up right away.

The sceptics amongst you may say, "But they're dogs, aren't they?' How many times do you think it takes humans to give up and succumb to similar levels of helplessness?

Dr Seligman wondered this as well, and so he tried a similar experiment where a group of volunteers were put into a room with eight doors leading out of it. All the doors were locked and then a deafening noise, like the sound of radio static, was played into the room. The volunteers all immediately scrambled to get out of the room but found the doors locked, so sat back down again and put up with the horrible noise. Just as they all sat back down, Dr Seligman went round and unlocked all of the eight doors. Over the next three hours, how many people got back up and tried the doors again, to see if there was any escape from the horrible noise?

None of them. They had learned to be helpless after just one attempt.

The point of these experiments is that we all have beliefs, which then drive our actions and behaviours to produce certain results.

When you talk about identifying your purpose in life and the goals you want to achieve, the beliefs you hold are the most important factor in achieving them. It is your own beliefs that decide whether you will be successful. The formula is simple: if you change the belief, you immediately change the behaviour and, therefore, you change the results you will enjoy.

Henry Ford was the pioneer behind the first mass-produced motor car. He had a clear goal – to make the car the mode of transport of the future – and he had to overcome a lot of initial scepticism. He remained true to his beliefs and didn't allow others to change them. He said:

It doesn't even matter if what you choose to believe is actually true or not. After all, you once believed that Father Christmas was real and your forefathers and ancestors once believed that the Earth was flat. If you do actually believe in something, at a deep, subconscious level, this belief will dictate how you behave, every minute of every day.

Talking of Father Christmas, think back to when you believed he was a real person. Do you remember how it affected your behaviour during December, when you believed that you wouldn't get any presents if you were badly behaved? This relates back to the formula:

In this case the result was presents from Father Christmas.

It is how you behave, on a regular and consistent basis, that decides the sort of results you get. Again, the formula is really simple. If you change the beliefs at one end, you change the results at the other.

As you go through life, many of the barriers and obstacles that stop you from being successful come from within your head. You create and set limits for yourself and then convince yourself that it's impossible to go beyond those limits.

Once these barriers are proven to be breakable, you often look back and realize that the barrier was self-imposed. It didn't exist in reality.

Homer Simpson understood this truth:

Let me offer you what I consider to be the most powerful example of how beliefs can affect results. This was a belief that humankind held and accepted as fact for centuries. Since humans started to be measured against the clock, no one had ever run a metric mile in under 4 minutes. On 5 May 1954, the world record for this distance was 4 minutes and 1.4 seconds. To run a mile in under 4 minutes was a barrier that many "experts" felt was impossible to cross. In fact, the British Medical Council "knew" that the human body couldn't run that fast.

The following day, a 25-year-old medical student called Roger Bannister ran a metric mile in 3 minutes and 59.4 seconds, a fraction of a second below the impossible barrier. What is most amazing about his feat is what followed it.

Within 46 days of Bannister breaking the record, a New Zealand athlete, John Landy, broke that record by running 3 minutes and 57.9 seconds. By the end of the year, two men – Bannister and Landy – had managed to break the 4-minute barrier in the same race. Astonishingly, by the end of 1957, just over two and a half years later, 16 runners had also gone on to beat the clock. The lid had been removed from the jar. By 1999, the world record for the distance had been lowered 19 times; to date over 955 athletes have run sub-4-minute miles, accomplishing what was formerly believed to be an impossible feat more than an amazing 4700 times.

Think about your own situation. What barriers are keeping you back?