Science Articles

Why all decisions aren't made equally

Mon, 8th Oct 2012

Morning selections are made more simply than those made last thing at night...

Ginny Smith

Historically, humans have been modelled as rational decision-making machines, that weigh the available evidence before making the most beneficial choice. This may also be how most of us like to see ourselves - it is much more comfortable to believe that the decision you have made is the best possible option, influenced only by the evidence. But psychological experiments show that this "Homus economicus" is in fact a figment of economists' imaginations, and we are influenced by many more factors than we would like to believe.

A cameraOne example is that of comparison. Given the choice between a £50 camera and a £100 camera, people are split reasonably evenly between the two. But when a £200 model is added to the mix, the majority plump for £100 version1.

And if you have ever been to buy a new television, you have probably experienced how reasonable the standard version seemed when compared to the brand new, state of the art version. Yet you probably didn't realise is that you may well have walked away with a more expensive TV than you otherwise would have, just because you compared it to an even pricier version!

Much of our decision making is unconscious and is guided by what are known as "heuristics". These are short-cuts which come into effect in situations where we do not have all the available information or where there is too much information to take into account. But heuristics are not necessarily a bad thing - they have evolved to be effective in the majority of situations, and in some situations rational and deliberative is, in fact, worse.

For instance, it's been shown that when making a difficult decision between 4 options, where 12 pieces of information have been provided about each, subjects made better choices when asked to carry out a memory task for 3 minutes than when they were allowed either 3 minutes to think about the problem or asked to make their decision straight away2.

This shows the amazing power of the subconscious mind to deliberate on difficult problems even when we are doing something different. Most people have had the experience of solving a crossword clue when coming back to the puzzle after doing something different for a while, and this is another example of the same thing - it is important to trust our instincts and unconscious judgements because, often, they know better than we do! We all know it is a good idea to sleep on a difficult problem, and this is for the same reason. Sleep allows our minds the chance to work away at the issue without interference from the conscious parts of our brain.

One recently discovered phenomenon that can affect our ability to make rational decisions is decision fatigue. If you have ever been to America you have probably experienced decision fatigue first hand. In the morning it can seem like a great idea to have 27 different options when you are ordering your coffee: it means you can make sure the cup is perfect for you. But after a hard day at work, or in your lunch break when you are starving and in a hurry, the decisions are less appealing. In this situation it can feel like you will just say "yes" to anything for an easy life (“do you want pickled rabbit's foot with that sir?” “yes, whatever, just give me my lunch!”).

This is an example of decision fatigue, and it is something that affects us all. During the course of a normal day we all have to make a multitude of decisions. Some of these are important; others are trivial; but they all use mental energy. We may not feel tired, but after making a series of decisions our mental reserves become depleted and our reasoning abilities are compromised. In this condition, we are more likely to make a reckless decision without thinking through the consequences, or avoid making any decision at all by sticking with the status quo.

A recent study looking into bail decisions made by judges3 over the course of the day revealed some surprising results. Most judges take 2 breaks for food during the day, giving 3 "decision sessions" each day. It was found that the percentage of decisions to grant bail dropped from around 65% to 0% over the course of each of these sessions, before rising to 65% again after the food break. In this situation the decision not to grant bail is the easier one, as it leaves the situation the same as it was before the hearing. Judges are a group of people chosen to be unemotional and rational, and to concentrate solely on the facts of the case. This study, however, showed that they are hugely affected by their personal circumstances, and decision fatigue, so make easier decisions towards the end of a session when they are more fatigued.

CakeThe judge study shows that it is not just the number of decisions we have made that affect our fatigue levels- they are also affected by blood glucose levels. People who have had to use their willpower to avoid eating tempting chocolates give up more quickly when presented with unsolvable problems4; the same thing is found when it comes to decision making, suggesting making decisions and exercising willpower may have similarities.

A group of students asked to make repeated decisions about a selection of items were able to hold their hands in iced water for less than half the time a control group – who just looked at the items – managed5.

So, if you have made a lot of decisions during the day, this may mean you are less able to stop yourself from indulging in a big slice of chocolate cake, or a glass of wine, that evening. In the cake example there is a slight paradox however, as the glucose contained in the cake would actually give you the boost you need to improve your willpower and decision making abilities!

This also works the other way around, so someone who is on a strict diet and denying themselves treats on a daily basis, may have reduced willpower6 and so be handicapped in their decision making abilities in two ways. First, the low blood sugar in itself may lead to poorer decisions, and second the willpower being used to stick to the diet will also be sapping mental energy, leading to a more rapid onset of decision fatigue.

So how can this knowledge help us to make more effective decisions? Well, it is probably a good idea to schedule any important decision making for the morning (after a good breakfast of course), and to avoid doing anything too taxing just before lunch or in the late afternoons. Diet is important, especially with the rise of obesity, but being sensible about it is vital - a low GI diet, which avoids fluctuating blood sugar levels, may be helpful, as may having a small, healthy snack before an important decision needs to be made.

And if you are going to have the occasional lapse in willpower (after all, we are only human), giving in to that amazing looking cake is probably better than deciding it’s a good idea to gamble all your savings on the lottery...


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