Acts_as_list with single table inheritance

I have a question about where to decorate my classes with acts_as_list.

I am using single table inheritance and i have a base class LookupItem.
There are 5 child classes: Priority, Probability, RiskRating, Status,
and
RiskManagementItem.

Each of these 5 items needs to act as a list. Should I use acts_as_list
on
each child class or should it go on the parent LookupItem class? I’m
guessing that it should go on the child classes, but I couldn’t find
anything concrete to point me in one direction or another.

Thanks,

jeremiah