Last Night's Television - My Supermodel Baby, BBC1; Horizon, BBC2

Take a look in the mirror

"Another day, another scanner," said Marcus du Sautoy in Horizon's "The Secret You". He could be forgiven for the faint weariness of tone in his voice. Horizon absolutely loves brain scanners and will rarely let an opportunity pass to slide a presenter into the magnetic doughnut and expose the inner workings of his or her brain. On this occasion, though, Horizon could be forgiven for its compulsion as well, since the subject of Du Sautoy's programme was consciousness, and the brain scanner may be to that conundrum what the telescope was for solar astronomy. Indeed, there were several experiments conducted here that would have been unthinkable or impractical only a few decades ago, using devices that would have appeared almost magical to early theorists of consciousness, like Descartes. He had to make do with a far older piece of equipment – the human brain – one that has proved marvellously effective over the centuries but rather gets in its own way when the issue at hand is thought itself. It's a bit like trying to take a picture of the television camera you're using to take the picture.

Mirrors help in such situations, and Du Sautoy started off with a bit of Consciousness 101, demonstrating a famously low-tech experiment in self-awareness that involves furtively dabbing a red spot on to children's faces and seeing whether they poke at it when they look at themselves. Somewhere between 18 and 24 months, it dawns on us that that isn't a another baby with sloppy hygiene over there but a reflection of us, though scientists still aren't very sure what achieves this fundamental leap in awareness, one we only share with chimpanzees and orang-utans. It's possible, I suppose, that everything else sees the spot and just isn't fussed about it, but I take it they've covered for that possibility somehow. After that, Du Sautoy was rigged up for a far more intriguing bit of trickery – donning a pair of video glasses that allowed his visual input to be detached from his physical sensations. Effectively, he was put inside someone else's head, looking at himself, and the effect was so persuasive that he winced when a knife was thrust towards his opposite number's arm.

A programme like this was never going to be able to arrive at a conclusion, only to mess with the smooth illusion of personal autonomy that nature has had thousands of years to paste into place. A scanner was involved in the most startling of those – a simple experiment in which the scientists were able to predict Du Sautoy's random choices between two options, a good six seconds before he even became aware he'd made them. His conscious self, the "I" he thought was taking all the decisions, was pretty much the last to know what was going to happen – a revelation that understandably made him sit down hard on the laboratory steps. Consciousness, it seems, is like a constitutional sovereign – the ceremonial part of the brain that gets to rubber stamp the decisions made by courtiers and happily convinces itself it's in charge when actually everything interesting is happening in some back room.

I would like to have run the parents in My Supermodel Baby through a brain scanner, because I suspect the monitor would have displayed a trans-cranial firework display of instinctive adoration. This is a common enough delusion in parents, charitably duped by evolution into believing that their own child is the most beautiful in the world. But the mothers and fathers in Jaclyn Parry's film had taken things one step further, so convinced of their children's charms that they had decided to put them up for baby-modelling assignments. "He's like a little Marlon Brandon, a little Brad Pitt, a little Elvis... He's unique," crooned Jamie, mother of Frankie, who eventually scooped a cover shot for Mother & Baby magazine. Meanwhile, Esther was pitching the charms of Hadley Jack, who lucked out when a competitor threw a Naomi Campbell, and eventually made it on to the cover of a rival publication. The arrival of both these magazines in the stores was greeted by their respective parents with the kind of bubbling giddy pride that would only be understandable if your child won an Oscar or a Nobel Prize, Esther dividing her delirious kisses between the real Hadley and the heavily airbrushed picture behind the plastic wrap. Frankie was half obscured by an Igglepiggle giveaway, but his mother wasn't dismayed. "He'll always have that, won't he?" she said, as if his life was already all but over. Fortunately for Frankie, his career soon will be, since the baby-model industry chews them up and spits them up quite ruthlessly. It was love at work, I suppose, but it was love just a whisker away from the kind of thing that can really screw you up for life.