Based on the additional tests, we can observe that the function assigns higher values to words that are associated with celestial objects like stars. The function also seems to have a preference for certain common objects like pens and books, although the association is not as strong as with celestial objects. 

Therefore, a good description for the function implemented by f(x) would be:

[DESCRIPTION]: The function f(x) appears to be selective for concepts related to celestial objects, with a stronger association for words like "sun" and "star." It also shows a mild preference for certain common objects like pens and books, although the association is not as strong compared to celestial objects.