08/08/2014 10:25 BST | Updated 07/10/2014 06:59 BST

Breaking the Cycle: Unlocking the Science of Bad Habits

We all have habits that we want to change: eat less, exercise more, stay out of our overdrafts; but this is easier said than done. Why is it that bad habits are so hard to break and new 'good' behaviours are so hard to stick to?

It comes down to our neural wiring. Our brains are set up to ensure our survival, and this means prioritising the functions that will keep us alive long enough to spread our genes - unsurprisingly eating ranks pretty highly. However, our tendency to overeat cannot fully be explained by a desire to maintain energy levels. There is another key neural property that helps to draw a clearer picture of our behaviour, and sheds light on how we might go about changing our bad habits in order to live healthier and more satisfying lives. This mechanism is known in the scientific literature as 'hyperbolic discounting'.

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Hyperbolic discounting is the tendency to overweight present rewards and undervalue future costs. Put simply, £100 now is better than £101 tomorrow, but add a year to both options and our preferences change. Kahneman and Tversky have produced the most well known work examining our non-linear decision preferences, demonstrating these results experimentally. These results apply not only to financial incentives, but also for any sort of reward that will activate our dopamine receptors, and it can cause us significant problems in decision-making.

Let's take overeating as an example, a problem that many people in the western world are familiar with. When we think about the benefit of consuming an extra donut, we imagine the satisfying taste, the sweetness and the texture, how good it will feel to eat. We might briefly weigh up how this act of consumption fits with our lifestyle objectives, but when that sugary delight is on a plate in front of us future goals are quickly forgotten. Overweighting present benefits is a problem, but failing to accurately evaluate future costs is almost as damaging. In the face of temptation we become incredibly short sighted - despite our best intentions.

Bad habits are difficult to break precisely because they usually involve some sort of 'instant gratification'. When the prize is right in front of us, the anticipation of consuming it releases dopamine in our brains, signalling reward - a phenomenon that has been documented not only in human behaviour, but also in apes, through the work of neuroscientist Wolfram Schultz. Ironically, the benefit actually comes from the anticipation of reward rather than the consumption, leading to an impossible cycle where we always want more.

So, we have a tendency to overweight reward, and get in to an insatiable gratification cycle- but the challenges to our diet and fitness plans don't end there. When we repeat a particular behaviour enough times, it becomes automatic. Essentially a neural pathway is formed in the brain, signalling us to make an associations between actions, for example 'go to fridge' and 'scavenge for snacks'. Furthermore, we become conditioned to associate these behaviours with reward, making it harder and harder over time to snap out of this cycle.

Breaking bad habits then becomes very difficult because it requires shifting from a more automatic reward based approach to taking a longer-term perspective, when our brains are wired to take the path of least resistance. Conversely, the problem with a lot of positive health behaviour, is that the benefits are not always immediately salient, and it can require a short term cost. Going for a run is not always pleasant, and while we know it is good for us, the future benefits can be difficult to quantify.

But, it is not all bad news. A better understanding of the neural mechanisms governing our behaviour can only help us to design interventions that will allow us to achieve our lifestyle goals, and to combat those inevitable moments of weakness. Furthermore, we can manipulate the same mechanisms that make us form bad habits, to enable us to form good ones - wiring ourselves for better health.