The function implemented by f(x) seems to be associating words with different concepts based on the given inputs. Here are the concepts that f(x) is selective for:

1. The concept of "reporting": The word "reporting" has a highly selective value of 0.9979, indicating a strong association with the concept of reporting.

2. The concept of "writing": The word "writing" has a moderately selective value of 0.6334, suggesting an association with the concept of writing.

3. The concept of "body armor": The phrase "body armor" has a selective value of 0.1711, indicating a moderate association with the concept of body armor.

Other words such as "Poseidon," "reference," "hypothesis," "old," "Passover," "green," and "physics" have relatively lower selective values, ranging from 0.0012 to 0.0619, indicating weaker associations with certain concepts.

It is important to note that the specific concepts associated with each word may require further exploration and experimentation to fully understand the function's behavior. Consider running additional tests with a diverse range of words to gain more insights into the function.