IS GEORGE W. BUSH stupid? It's a question that occupied a good many minds of all political persuasions during his turbulent eight-year presidency. The strict answer is no. Bush's IQ score is estimated to be above 120, which suggests intelligence in the top 10 per cent of the population. But this, surely, does not tell the whole story. Even those sympathetic to the former president have acknowledged that as a thinker and decision-maker he is not all there.

How can someone with a high IQ have these kinds of intellectual deficiencies? Put another way, how can a "smart" person act foolishly?

IQ tests fall down when it comes to measuring those abilities crucial to making good judgements in real-life situations. That's because they are unable to assess things such as a person's ability to critically weigh up information, or whether an individual can override the intuitive cognitive biases that can lead us astray.

"IQ tests measure an important domain of cognitive functioning and they are moderately good at predicting academic and work success. But they are incomplete. They fall short of the full panoply of skills that would come under the rubric of 'good thinking'."