An inherent problem in Psychology is that the more general the issue, the harder it is to examine. Take the question ‘what do women find attractive in men?’. People who have read a little about the subject will often trot out a list of things that women rate as most attractive in surveys – good sense of humour, trim bottom and waist, ability to listen, etc.  This is all fine and dandy, but does it hold universally true? In other words, if several women were selected at random, would their list of likes exactly match this list? The answer is, of course not. Personal experiences might bias someone strongly in a particular direction, there might be specific cultural or familial factors that shape taste, and so on and so forth. Similarly, other general questions, such as ‘what makes us smart?’ or ‘why do some victims of child abuse become abusers and others don’t?’ are resistant to answers that automatically cover everyone. We can find a set of rules that apply reasonably well to groups, but we can never find rules that automatically apply to individuals.

In part this is the problem of statistics. As has been noted in earlier blogs, statistical tests measure how likely something is to occur again under similar circumstances. They don’t say that it inevitably will, nor do they say that every single participant in a group will do the same thing (indeed, one of the great advantages of statistical testing is that it can in effect weed out the effect of what are seen as ‘atypical’ scores).

‘Whoa!’ I can hear you say as you read this. ‘You’re not exactly giving a good advert for your subject. Are you in effect saying that Psychology can only offer useless generalisations?’.  Well, it all depends what you mean by ‘useless generalisation’. Penicillin is a highly effective antibiotic. Except that a significant minority of people (this author included) are violently allergic to it. But would anyone like to claim that ‘penicillin is a highly effective antibiotic’ is a ‘useless generalisation’? A lot of arguments from the biological sciences are also generalisations in the sense that there will be exceptions to the rule. Dolphins are on the whole intelligent creatures, but they can be incredibly dumb on occasions and also very sadistic. Global warming is not a good thing, but one result of it might well be an increase in life expectancy in many parts of the world. We cannot look at scientific arguments based on living beings and then be amazed when there are exceptions to the rule.

This does not mean we can be totally complacent, however. Take the reports that appear almost daily in the news media about how X has been linked to one disease or another, where X is a commonly-consumed food item or drug. If we took every one of these reports to heart, there is practically nothing on this planet we could consume. Luckily this is counter-balanced by almost an equal number of reports on how X prolongs life. How many times over the years have we been told that coffee is bad for us in one report, and good for us in another? To this list can be added statins, aspirin, red meat, red wine, sugar, saturated fat, etc, etc, etc.  How can we work out what is true?

The simple answer is that we cannot do this very easily, but it pays to look at how many of these studies are conducted. Typically, researchers monitor what people consume at the start of the study, and also take measures of other key factors such as body mass index, socio-economic status, and so forth. Then, some time later, the same people are assessed for their health, and this is matched to the measures taken at the start of the study. What will inevitably be found is a general pattern (e.g. ‘people who eat more than X grams of saturated fat a day have a Y% greater risk of developing heart disease’). But this will not be a firm inviolable rule (e.g. ‘if you eat above X grams of saturated fat a day, you will die of a heart attack in five years’) and some people will be found who eat their own bodyweight in fat and never have a day’s illness, whilst others eat barely any fat at all and yet develop heart problems.

The main reason why this happens is that other factors are also at play that the researchers have not measured. For example, it is quite possible that a person on a fat-free diet might have had anorexia nervosa and it is this that caused the heart problems. Again, people who have a high fat intake might be heavily reliant on convenience foods. This can be indicative of low socio-economic status and/or a very rushed life. Both of these can lead to high levels of stress, and perhaps this is the cause, not the fat.

So how on earth can health psychologists advise on healthy behaviour? Or for that matter, how can psychologists advise on behaviour in general? In fact, this is asking the wrong question. It assumes that psychologists can only respond in one way. For example, if a person is obese, it’s not enough to lecture them on the evils of fat and sugar and think that will do the trick. Other lifestyle and mental factors must be taken into account as well. Likewise, not everyone will respond to the same psychological therapies. For example, many therapies are useless on psychologists. If I may speak for my people, we can see what the therapist is doing a mile off and adjust our mental defences accordingly. But nonetheless, individuals can be helped.  Just because theories are usually generalisations does not mean the exceptions are beyond Psychology’s scope.

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