gnus-use-adaptive-scoring

gnus-use-adaptive-scoring is a variable defined in `gnus.el'.
Its value is

nil

Documentation:
*If non-nil, use some adaptive scoring scheme.
If a list, then the values `word' and `line' are meaningful. The
former will perform adaption on individual words in the subject
header while `line' will perform adaption on several headers.

You can customize this variable.