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[raghusesha]

I think this is more to do with the time some of the subjects got while washing their hands.  Was the same effect seen when the subjects were asked to simply walk in a garden for some time instead of actually washing their hands?

[chris]

That's a good point, but actually they controlled for this in a couple of ways; one was to use another (non-handwashing) task as a comparison, which didn't show the same effect; another was to insert a distractor / intervening task between the handwashing (or not) and the re-test. If it were purely distraction then you'd expect both conditions to behave identically, but the handwashing effect still held.

Chris

[imatfaal]

Change of blood circulation - hot water and vigorous hand-movements would get more blood to hands and skin.  Perhaps enough to provide a minuscule change in blood chemistry at a tipping point in the brain?

Just been to wash my hands and whilst it is second nature - it also requires a fair amount of concentration and it is quite sensuous.  I think it is the distraction that causes a mental reboot; a walk in the garden allows the brain to stew on a decision whereas the washing of hands causes a "redo from start". 

I often go for quick walk around block when I have a tight decision to make at work - now I think I might pair it up with washing face and hands - Matthew