In the movie - Inception, who decides how a totem behaves inside a dream?
First of all, in the dream, are the totems manifestations of the dreamer? The architect creates the other parts and constructs in the dream but the dreamers would need to manifest their totems, yes? If that is not the case and the architect has to add the totem to the dream which then leaves for the architect to decide the default behavior of the totem.
If the architect decides the default behavior of a Totem, then a top would be designed to stop and not keep spinning. This would however work for the other totems. The default loading on the die would be uniform and the difference in loading of the die between the dream and real world would let Arthur know if he's awake or not. Also, the architect's own totem, Ariadne knows how her chess pawn is loaded, wouldn't that confuse her between the dream and the real world?
If the dreamer manifested the totem and controlled its behavior, Cobb could keep spinning the top in a dream and can't in the real world. This would help him say he's awake or dreaming. But the problem is, he could "think" his top to a stop, which would mess things up for Cobb. Arthur's die would be a problem too, he could end up "thinking" the loading of his die as it is in the real world, that would put Arthur in trouble.
So to sum it up, who exactly decides the default behavior of everyone's totems to help them confirm if they are awake or not?