Rule6: The factors deciding the quality of a concept include the syntactic simplicity of the term and the average sharpness or quality of the beliefs contributing to the meaning of the concept. The latter can be updated each time a belief is inserted or accessed, using a formula similar to that of the above durability.
The formula for concept with quality $q$, given task with quality $q'$ is $q = u_q \times q' +(1-u_q)\times q$, where the updating rate $u_q$ is a system parameter
Technical Report
More Info
It seems Concept quality is not updated.