Some creatures are so dull of mind that events on the battlefield can sometimes leave them rather distracted and confused.
Models that are subject to Stupidity are also– they just don't get frightened that easily, and by the time they do, it's normally too late.
Provided that they are not engaged in close combat, a unit that contains one or more models with the Stupidity special rule must try to overcome its Stupidity at the start of its turn by taking a Leadership test. If the test is passed, all is well – the creatures have risen above their dull-witted nature and will act normally. If the test is failed, the warriors succumb to their stupidity and amble forward, perhaps drooling a little, eating grass or cackling in silly voices, as explained below.
Me 'Ead 'Urts
A unit that fails its Stupidity test immediately stumbles D6" directly forwards – this move is otherwise treated in exactly the same manner as a failed charge. The Stupid unit cannot take any further action that turn, so cannot declare charges or make a shooting attack. Wizards that have failed a Stupidity test cannot attempt to cast or channel power dice or dispel dice until a Stupidity test is passed (there's a lot of hand waving and chanting, but for some reason the magic just doesn't seem to work).