I have often heard, over the years, when two parties are in disputation, one side saying that the issue would be easily resolved if only the other showed some “common sense”. Whilst I am sure that they did not consciously mean it, what was being implied was that what the aggrieved party believed is “common sense”, and what the protagonist believed is somehow aberrant.

Albert Einstein said that “Common sense is the collection of prejudices acquired by age eighteen.”

It is one the most difficult dilemmas confronting mankind that we seek to pursue our commonality but at the same time striving to preserve and often exaggerating our individuality. We flock to our common beliefs be they religion, politics or nationality. But we still want to demonstrate our individuality – our particular skills, strengths, beliefs, which seem to make us who we are as an individual. Then we come to the uncomfortable position that those things that we believe fervently must be true and therefore those that don’t agree with us must somehow be fools!

What we believe as individuals will often set us apart from our friends, colleagues and acquaintances. We are normally happy to deal with these anomalies in beliefs. We say, “Claude can’t help his Catholic upbringing” or “Rachel is a prisoner to her Jewish background.”

We are not normally too critical of these individual beliefs. But when it comes to judging the collective, we are far more judgmental.

But it is instructive to understand how we come to our beliefs. Much of what we believe is based on anecdotal evidence and very small samples. And often we believe what is convenient for us to believe.

Recently we have had the phenomenon of power bands. Many sports people, some with international reputations, endorsed the product which was supposed to improve their balance, strength and flexibility. There was no research to support such claims. Eventually consumer organisations did scientifically test the product and the manufacturer was forced to reimburse buyers and retract their claims regarding the products effectiveness. No doubt some of the purchasers, with no supporting evidence, believed in the product’s efficacy. If I had purchased the product and had a good day on the football field, I would have been tempted to assert that the product was responsible and even more than that I would have evoked “common sense” for the reason that I believed so.

In the aftermath of the terrorist attacks on the twin towers in September 2001 many Americans curtailed their flying. They probably would have said it was common sense to do so. As a result many more were compelled to drive long distances to meet business commitment and for family and leisure reasons. Consequently the road toll went up dramatically. Despite the terrorist attacks it was still much safer to fly than to drive but “common sense” compelled them to do otherwise. Psychologist Gerd Gigerenzer from the Max Planck Institute in Berlin who researched the phenomenon calculated that in the twelve months after the terrorist attacks an additional 1595 Americans died in car accidents above the projected deaths that would have occurred if the levels of car travel hadn’t been increased by those now afraid to travel by air. “Common sense” let these people down.

An article in “The Australian” of 31/12/2010 quotes some celebrities on health issues. One film star reports, “When I was young, I heard of only one person who had cancer in all my growing up years.” She then asserts that, what she sees as the growing incidence of cancer, must be due to the growth hormones in the food we eat! But of course an aging population and better detection methods mean that more people will be diagnosed with the disease. The article goes on to describe other mistaken conclusions celebrities have drawn from their personal experiences with alternative health practices. No doubt they would have asserted it is only “common sense” to believe what they do.

You will see from the above examples that a major threat to common sense’s ability to provide sensible outcomes for us is that people are not well-equipped to estimate risk.

For example a 2007 survey by Oxford University asked women when a woman is most likely to get breast cancer. More than half said age does not matter. When asked to estimate the risk in varying age groups they nominated declining rates for women after their fifties. In fact the risk of breast cancer increases with age. Common sense erred again!

In Australia despite concerns about global warming and the impact of carbon dioxide emissions on climate we display a great anathema to nuclear power. This remains the case despite the fact that nuclear power has been a major source of power for France and Japan for decades. So whilst we tremble at the thought of nuclear reactors we shrug off concerns about having X-rays which are similar to the radiation we fear exposure to in a nuclear power station mishap. And of course there was a huge disaster at Chernobyl and we can’t deny that. But evidence suggests that where proper engineering standards are applied the risk is acceptable. Common sense won’t buy that!

There is a very vocal contingent currently opposing the use of genetically modified crops, despite the fact that I have not seen a single scientifically verifiable report that these products are harmful. But then common sense says we shouldn’t tamper with Nature.

So then what we call “common sense” is often based on anecdotal evidence generally gleaned from those we know and whose judgment we (often irrationally) trust and not backed by proper analysis. We are often unduly influenced by the media. Terrorist attacks are more newsworthy than car accidents. Car accidents are more newsworthy than obesity, diabetes or influenza which kill untold more people than the more newsworthy means.

Why then do make such poor judgments in many of these important areas? “One of psychology’s fundamental insights,” writes Harvard psychologist Daniel Gilbert, “is that judgments are generally the products of nonconscious systems that operate quickly, on the basis of scant evidence, and in a routine manner….”

This is really not surprising. Our ancestors, who were hunter gatherers, did not have the luxury of deliberating long over whether that thing moving in the grass nearby was a lion or an antelope. A quick response was required if they were going to survive in that hostile environment. Generally, also, there was not a lot of data to support the decision that they made. In such circumstances it was helpful to be not only quick, but conservative in our decision making. This seems to be the decision making framework we have inherited for those things we regard as threatening. We rely on scant information, make the decision quickly and err on the side of conservatism. Unfortunately in today’s environment, which is considerably less threatening, where we could take the time to weigh up the evidence, and do some proper analysis, we still are often prone to use the same processes for decision making.

And then of course, when under these curtailed and often inaccurate deliberations we come to a conclusion, we are egotistical enough to label our instinctual response as “common sense”.