The function f(x) appears to be selective for the concept of objects, materials, or phenomena that have a strong or significant physical presence. Examples of such concepts include "war", "steel", "red", "wood", and "grass". These concepts tend to have values closer to 1, making the function selective for them. Other concepts, such as emotions, technologies, and abstract notions, produce values relatively closer to 0.

However, it's also worth noting that the function allows for some variability, with concepts like "pain", "joy", and "love" receiving relatively higher scores, but not as high as those listed above. The function seems to prioritize physical presence or perceptibility over abstract or intangible qualities.