I don't think commentators have drawn the right inferences from the mess May made over social care policy.

The problem is not that she made a U-turn: if you're heading in the wrong direction, a U-turn is a good idea. Instead, the episode reveals a fundamental failure in how May makes policy.

The Times reports that "few were asked in advance" about the dementia tax, and says the secrecy of May's inner circle "has become notorious". The FT reports a "senior Tory" as saying that the policy "wasn't really run by anyone outside the inner circle." And the Guardian says:

Conservative insiders under [Nick] Timothy and [Fiona] Hill talk of a disciplined atmosphere and often highly pressurised blame culture, where people from advisers to ministers fear receiving a dressing-down for stepping out of line or veering off script.

All this suggests to me three related errors. One is taking a decision in haste. Sam Blainey writes:

The social care proposals were, apparently, a last-minute addition placed there at the behest of Nick Timothy, the Prime Minister's powerful joint chief of staff. But this means they will not have been stress tested to destruction. Consulting with your colleagues may be tiresome and dull, but an hour-long meeting to discuss some of the Tory plans would have allowed them to address and hammer out any problems.

Secondly, there is what the FT describes as a "disdain" for the advice of some "experts." However, if you need a quick decision the natural thing to do is to adopt the proposal of someone who has gathered evidence and thought long and hard about the issue, as Andrew Dilnot has. Believing that one's own snap judgment is better than his is an example of egregious over-confidence.

Thirdly, tight-knit groups lack the cognitive diversity to take good decisions; nobody in May's inner-circle seems to have stood up to Timothy's suggestion. As Iain Martin says, "Team May is way too narrow in its composition." The FT quotes Lord Ricketts, former head of the Foreign Office:

Surely one of the lessons learned from this is that you can't do this in tight secret groups without consultation and without talking to political colleagues.

In short, what we have is an example of groupthink. Irving Janis wrote:

The advantages of having decisions made by groups are often lost because of psychological pressures that arise when members work closely together, share the same values, and above all face a crisis situation in which everyone is subjected to stresses that generate a strong need for affiliation. In these circumstances, as conformity pressures begin to dominate, groupthink and the attendant deterioration of decision-making set in (Groupthink, p 12-13)

From this perspective, I find it hard to excuse May's conduct. Politics is an activity is which some errors are inevitable: social affairs are complex processes which are often unmanageable and unpredictable; all large organizations such as government departments by their very nature contain some dysfunctionality; and there are what Harold Macmillan called "events, dear boy." Faced with this, Prime Ministers should at least not add to these unavoidable errors by making avoidable ones. They should learn from history and from research into cognitive biases.

And this is what May hasn't done: Janis wrote Groupthink way back in 1982. Anyone who aspires to be in a position to take decisions should know it. Yet May seems not to. She failed to avoid errors which were well-known to anybody who knew anything about the history and psychology of decision-making.

Mistakes I can forgive. Illiteracy and ignorance, however, are another matter.

You might think I'm making a partisan point here. I'm not so sure. May has done what Blair did when he went to war in Iraq: he too ignored well-known principles of good decision-making.

This alerts us to the possibility that our political system does not adequately weed out irrationalities. Last year, I wrote:

Chilcot...poses a systemic question: how can we ensure that political structures favour rational decision-making? This question will, of course, be ignored.

That looks like a rare correct prediction. And it'll remain the case until the media and voters understand leadership better. "Strong" leadership isn't about delivering diktats from on high. It's about taking good decisions, which often requires openness, diversity and being awake to cognitive biases. It's not clear that May can do this. And this is not entirely her personal fault.