It is a common misconception that we know our own minds. As I move around the world, walking and talking, I experience myself thinking thoughts. "What shall I have for lunch?", I ask myself. Or I think, "I wonder why she did that?" and try and figure it out. It is natural to assume that this experience of myself is a complete report of my mind. It is natural, but wrong.

There's an under-mind, all psychologists agree – an unconscious which does a lot of the heavy lifting in the process of thinking. If I ask myself what is the capital of France the answer just comes to mind – Paris! If I decide to wiggle my fingers, they move back and forth in a complex pattern that I didn't consciously prepare, but which was delivered for my use by the unconscious.

The big debate in psychology is exactly what is done by the unconscious, and what requires conscious thought. Or to use the title of a notable paper on the topic, 'Is the unconscious smart or dumb?' One popular view is that the unconscious can prepare simple stimulus-response actions, deliver basic facts, recognise objects and carry out practised movements. Complex cognition involving planning, logical reasoning and combining ideas, on the other hand, requires conscious thought.