A total of 97 MPs were asked this probability problem: if you spin a coin twice, what is the probability of getting two heads?
Among Conservative members, 47% gave the wrong answer, which is disappointing enough. But of the 44 Labour MPs who took part, 77% answered incorrectly.
It does explain a few things though- the basic innumeracy could be one of the reasons why Labour always propose spending bonanzas that are vastly greater than any real increase in wealth- and why Labour governments always leave economic catastrophes behind them.
I am being serious here- the inability to think past stage one is evident in a lot of Labour's previous actions and at the ideas on show at their conference this week- registering journalists, spending all the 4G money on one particular pet project etc, etc.
Humans use two mental methods for reaching conclusions- the one we use most often is intuitive and takes little effort. This means it is often wrong. The slower method uses reasoning and logic- this is hard work but tends to be right more often.