It is reasonable to believe that any cogniti ve ability consists entirely of knowl
edge
of how to do something. That knowledge is made up of a structure of
elements of knowledge, a structure of relations between concepts and ideas. By
testing exam
inees for possession of a sample of those elements, one can deter
mine the extent and strength
of their structures of knowledge relevant to the
ability and, thus, the degree to which they possess the abi lity.