The Best Predictor of Future Behaviour Is Past Behaviour. Or Is It?

Author: Nicole Porter, N.A. PORTER & ASSOCIATES

When you want to predict how a person will react in the future, experts generally agree it’s best to turn an eye to the past. Looking at how the person has acted previously can lead to a fairly accurate prediction of future behaviour. After all, the past generally repeats itself, doesn’t it? 

You’ve perhaps already heard the mantra: Past as prelude. Such a simple way of describing such a difficult process. Sure, the best predictor of future behaviour is past behaviour… but how easy, or difficult of a process is it for experts to determine this? 

Logically speaking, if a person who has psychotic tendencies has a history of violent offenses, it makes sense to assume they would re-offend in a similar manner. But if you predict future violence based on a certain set of risk factors, you will be wrong more often than not.

Only about 4 out of 10 of those individuals judged to be at moderate to high risk of future violence go on to re-offend violently, according to research. Therefore, it’s the low base rates of violent recidivism that could be working against you.

So where does this idea that “the best predictor of future behaviour is past behaviour” come from, and does it stand true today?

It appears the principle has circulated for decades. In fact, you’ll find it in most modern modern psychology textbooks and major academic literature. However, as it gained traction, some narrowed it down further; this boiled down to a one-size-fits-all mantra instead. So, there was no room for interpretation or scientific evidence. Post 2003, many publications claimed that, “when it comes to human beings, the best predictor of future behaviour is past behaviour.” Period. End of story.

But this is a gross over-simplification.

Psychological scientists who study human behaviour agree that past behaviour is definitely a useful marker for future behaviour. But only under certain specific conditions. For example, habitual behaviours are more predictive than infrequent ones. In addition, the person must essentially remain unchanged and the anticipated scenario must be essentially the same as the past situation that activated the behaviour.

Studies showed that over longer time periods, even high frequency, habitual behaviours may undergo dramatic change. A smoker or heavy drinker might successfully or suddenly quit the habit. A chronic thief might land a decent job, start a family, and settle down.

Also important to note, as this last example suggests, is that researchers have also determined that the situation plays a critical role. The situation is often more determinative than individual character traits.  So, for example, a person may engage in heavy drug use when in the company of drug-using peers, but may stop using when she moves away and gets a fulfilling job.

Confusion tends to set in when a potential risk marker is mistaken for an inevitability. It IS true that people with a history of violence have a higher likelihood of committing violence in the future than do people who habitually turn the other cheek. Risk is especially acute for those with very extensive histories of violence across a range of scenarios. But this does not mean that everyone who has committed past acts of violence will continue to aggress forever. 

That would be like claiming to know that because your teenage neighbor had a couple fender benders when he was first learning to drive, he would definitely crash his car again. He may understandably be at a higher risk of another collision than his middle-aged mother, with her clean driving record. However, he may or may not crash again. There are many intervening variables—whether he learned from his mistakes, the frequency and locations and times of day of his future driving, his choice of companions, the actions of other drivers on the road, driver training, the weather conditions, and so on.

If we know the base rate of the criminal behaviour we are trying to predict—whether murder or sex offending or general violence—and we know the frequency with which a person has engaged in that behaviour, we can use a mathematical formula, such as Bayes’s theorem to calculate a rough likelihood of the behaviour’s reoccurrences.

This maxim also snubs its nose at the age-crime curve, perhaps the most universal finding of a century of criminology research. As they reach their mid-30s or so, criminal offenders begin to slow down. Some mature naturally, some go through successful mentorship or treatment programs, some settle down and have families, some make mellower friendships, some simply burn out. Whatever the reasons, as research by Maruna, Sampson and Laub drives home, desistance is a virtual inevitability for all but the most die-hard minority of offenders.

But sometimes, folks, a ticking time bomb fails to ignite. 

Consider this scenario: Guy gets out of jail and does great. He voluntarily sought treatment and cooperated with all terms of his supervision. By the time experts saw him, he was leading a life as peaceable as a newborn baby. In his spare time, he even volunteered to help the needy at his local community church.

If the evaluator had heeded the literature on criminal desistance, she might have seen this coming. The fellow had reached the age at which desistance becomes more the rule than the exception. He therefore no longer associated with his old criminal peers and perhaps most importantly, he had stopped using the drugs that had exacerbated his form of persistent psychosis.

The past-as-prelude mantra fits with today’s dominant, dark view of offenders as a bundle of perpetual risk factors, ticking time bombs just waiting to explode. But it doesn’t exactly work out that way in reality, as experts often find.