Based on the tests conducted, it seems that the function f(x) is selective for a few concepts, including:

1. Outdoors and nature-related concepts: Words like excavation (0.9939), outdoors (0.4036), mountain (0.5699), and desert (0.2227) have higher values close to 1. 

2. Some animals: tiger (0.3174) and lion (0.2751)

3. Emotional concepts: trust (0.2659), fear (0.1366), and anticipation (0.1582) have relatively higher values.

[DESCRIPTION]: The function f(x) appears to be selective for words related to outdoors or natural landscapes, certain animals (particularly larger predators), and certain emotional concepts. However, the function may be less selective to these groups and more focused on specific examples within them.