Figure 2. Representatives of different families and orders show the most specific morphological markers of domestication, white spotting on the head (top row) and floppy ears (bottom row):

Horse, cow, pig, sheep, dog, and rabbit.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763232/

All behavioral traits have a direct relationship to phenotype.

What other at all reasonable way could it work?