By Cynthia McVey, former head of psychology at Glasgow Caledonian University, prior to retirement

The way people perceive social problems can depend on a number of factors, such as their personality type, media coverage and publicity surrounding a topic and other environmental factors.

If you are a glass half full type person you may underestimate the prevalence of an issue such as teen pregnancy, whereas a glass half empty person may be more likely to pay attention to the negatives – or even attribute negatives that don't exist.

In general people who tend to focus on to the worst case scenario may overlook the positives. So if you read two articles and one says things are OK, the other says they are not great, they pay more attention to the one which is more pessimistic.

READ MORE: Why Scots' foolish notions show Burns was right about seeing ourselves as others see us

With regard to the views expressed about obesity, it may be that because we have an obesity problem in Scotland, we are more familiar with seeing it. As a result, we are more likely to identify someone as average, rather than tending towards obesity – if it is the social norm in your area, or within your family, for example, you see it but don't notice it. People don't always believe the statistics.

In relation to the statistics themselves, it may not be an issue about mathematical literacy, so much as a failure to go to the heart of the matter, or pay enough attention. So you might stop reading about a topic before you find out what the statistics are. People are busy and don't always have the time to take in the detail.

You read an article about obesity, say, but then you get to the complex statistics and people can be put off. Unless you are a health professional or have a vested interest in the topic, there is a risk that you switch off.

But there is another possibility which is that people who fear they are obese themselves, may not want to read statistics about obesity that might make you feel uncomfortable.

It is common for people to suffer from "cognitive dissonance", when their attitude or knowledge conflicts with the way they behave, or they way they are. For example if you smoke, you may well know the harm it does but make excuses, such as: "if I give up I will collapse with stress," or "I will overeat" or "I'll be awful to my partner and they will leave me." So you avoid paying attention to material that tells you something about you is not good.

READ MORE: Why Scots' foolish notions show Burns was right about seeing ourselves as others see us

While it may seem that the way people perceive social issue is at odds with reality, the fact is that personalities and the environment we live in can have an impact on people's perceptions of these issues. The way people experience the world an be very relative.

Cynthia McVey was head of psychology at Glasgow Caledonian University, prior to retirement.