I think it is generally accepted that nervous cattle do not perform as well. Same with people I think. Happy calm cattle and people perform better. Extreme of this in cattle is a "dark cutter" at slaughter.Is there also correlation between tenderness and temperament-I would say yes. Low-key cattle gain more easily (not stress-burning calories). The heifer we butchered would cycle but never settle, she wasn’t as tender as our young bull or steers.