Based on the collected data, it seems that the function f(x) is selective for the following concepts:

1. Geometric shapes: words such as square, triangle, circle, and polygon had higher output values.
2. Colors: words such as red, yellow, and sun (associated with yellow) had higher output values.

The other tested words did not consistently output high values, signifying a lower association with other concepts.

[DESCRIPTION]: The function f(x) is selective for geometric shapes and colors, assigning higher output values to these types of words, while yielding lower output values for other unrelated words.