Last night's viewing - Horizon: Out of Control? BBC2 Letting Go, BBC1

There was a startling moment at the beginning of Horizon: Out of Control? when it sounded as if the BBC's premium science strand had found God. "At every moment of our lives an unseen presence is guiding us," said the narrator.

It isn't half going to simplify matters if they have, I thought. No more complicated and provisional accounts of the mysteries of the material world. No more painstakingly verified answers to the myriad "Whys" that make up the frontier of our knowledge. Just, "It's like that because that's the way God made it". Fortunately, it was just toying with us. The unseen presence was our own unconscious mind, which received opinion treats as some hindbrain hooligan (all base instincts and furtive desire) but that may actually turn out to be the secret CEO of Us Incorporated.

It began, pleasingly, with an experiment designed to test the limits of conscious alertness. It turned out that we can pay attention to between two or three things at a time, in a world that throws thousands at us every second. The illusion that we've got everything covered is just that – a brilliant bit of spinning by the brain that may operate something like the dummy steering wheel you put on the back of a car seat for children, to keep them quiet while the real driving is going on up front. And while our conscious minds might not be quite as powerless as a toddler strapped into a booster seat, they do a lot less than we might imagine.

The neuroscientists and researchers who took part in this programme were invited to graphically represent the amount of the brain devoted to conscious thought as a proportion of a blank sheet of white paper. Nobody shaded off more than 10 per cent and in most cases knowing was just a thin skin on the top of unknowing. The method wasn't exactly a model of scientific exactitude ("Are you serious?" one man said incredulously) but it did give a sense of an iceberg of sentience, with much of our perception and actions operating below the waterline of awareness.

What's more, the unconscious appears to be keeping things from us. Another test demonstrated the mind's tendency to favour positive information over negative, the latter being tacitly edited out. When we say, "It's being so cheerful that keeps me going", we may be expressing a deeper truth about how the mind has evolved to persuade us that the future will be better than the past. Horizon concluded with a study of an attempt to get under the hood and rewire the unconscious brain (to help a classical guitarist cope with performance "yips") and a US Army programme that plans to tap into its processing power directly, cutting out the lumbering middle man of the conscious mind. I liked this programme, but I was left with the nagging sensation that it wasn't me that was doing the liking at all... and that the silent partner in the back room might just be distracting me from something I ought to be paying more attention to.

In Letting Go, Rosa Monckton gave us the third of a series of documentaries in which she has united pointed personal experience with a larger campaigning zeal. The issue is the rights of disabled people, something she knows about directly as the mother of a Down's syndrome daughter, Domenica. Domenica is now 16 years old and Monckton has to begin thinking about how she enters adulthood and moves towards a more independent life. "All she wants to do is be a star on the West End stage," said Monckton of her daughter – a possibility that she knows to be remote but an ambition she understandably doesn't want to steal from her. As in her previous films, the painful evidence of how cruel people can be was mitigated by repeated proof of how loving families are. But they deserve the comfort of strangers too.