Horizon: Are You Good or Evil?, BBC Two

Scientists, eh? You can’t live with them and you can’t live without them: they cure life-threatening diseases and they threaten life with ever more powerful weapons. And in the instance of this documentary, they state the bloody obvious and then go to elaborate lengths to prove that their statements of the bloody obvious are objectively correct.

Even during the riots of a few weeks ago, most of those angry, jubilant or opportunistic individuals involved would have justified their actions to themselves. Even the organised criminals methodically emptying Currys were thinking of the holiday they’d be able to warm-heartedly give the wife and kids, weighed against the small dent they were making on the income of a huge corporation. The human animal is a moral animal because that’s what allows the human animal to survive and prosper - end of story. But as last night’s Horizon demonstrated; there are many inventive and elaborate ways scientists find to make absolutely certain that what we knew all along is the uncontrovertible truth.

So, Scientist One created a virtual reality scenario in which a group of volunteers were plunged into a situation in which they had to decide whether to save several people from a rogue gunman by sacrificing one person. Conclusion: people care about the wellbeing of other people, and try to do what’s best. Who’d have thought?

Then Scientist Two stuck some babies in front of a puppet show in which one of the puppets behaved badly. He then got the babies to (as best they could) point to the puppet they disliked the most. Conclusion: babies don’t like the bad guy… Although some of them did… And some of them didn’t really seem to know what was going on. But surely the bad guy can be seen as cool, more colourful and with more entertainment value? And even if the majority of the toddlers had gone for the bad puppet it wouldn’t have been evidence that they were likely to turn into Fred West when they grew up. My final conclusion: decidedly inconclusive.

Moving swiftly on, Scientist Three found that a group of rugby players needed to work together to succeed, Scientist Four found out that psychotic killers lacked empathy, didn’t have a conscience, could be charming and intelligent, and – surprise, surprise – don’t necessarily look like monsters. And so on. You can probably see a pattern emerging in this review: basically, I’ve been putting foward evidence that supports my initial thesis. It takes one to know one, I suppose. But to be fair, this wasn't all going over familiar ground; I hadn’t heard of the “moral molecule” before. And the idea that a brain scan can reveal which of us is a potential serial killer was chilling food for thought.

Which brings us to Scientist Five. By a quirk of fate, neuroscientist Jim Fallon found himself moving from being a specialist in standard clinical disorders to staring at the psychedelically hued brain scans of serial killers. Then one day his mother suggested he take a look at his own family history, as a cousin of his had murdered her parents. In a twist the poorest Hollywood scriptwriter would have blushed at coming up with, it turned out that Fallon had a cupboard bursting with literal family skeletons. There’d been at least 16 murders in his family history, his own brain scan had “serial killer” written all over it, and to top it all he also had all of the high-risk genes associated with the serial killer. We were told that the odds of having such a profile were millions to one.

But how much more unlikely was this blackly comic scenario in which Fallon had become the subject of his own highly specialised research? Amusingly, his family – on hearing the bad news - seemed to take some pleasure in talking to camera about how “scary”, “stand-offish” and “hot-headed” he could be. Fallon could only take solace in the fact that he was in late middle age and yet hadn’t got round to bludgeoning anyone to death. So why wasn’t this great big bear of a man a serial killer?

Well, once again your common sense will probably have given you the answer before you’re informed of the scenic route our friends in white lab coats took to get there: you can have the wrong genes, the wrong chemicals and bits of your brain scan the wrong colour, but unless you also had the wrong childhood, the wrong marriage or fought in the wrong war, things will probably turn out OK for you. Nature, nurture, free will, what side of the bed you got out of this morning - there’s just too much fuzzy greyness for black-and-white science to deal with in matters related to the mind and - for want of a better word – the soul than this week's Horizon could get to grips with.