I've certainly noticed different personalities in some of my dogs - I wrote a post on it some time ago (possibly the one PALU is referring to) on the old forum:
http://z3.invisionfree.com/UrW_forum/index.php?showtopic=8145While it's hard to be sure if the traits are actually there or just the result of confirmation bias, the main traits I've observed that appear to be on a range are:
Courageous versus cowardly (how long the dog continues to fight before fleeing due to wounds)
Gluttonous versus light eater (how long the dog goes before barking for food, stealing food or eating unusual foods)
Aggressive versus calm (how much damage the dog does to prey, quickness to attack, time to calm down, likelihood of attacking its master)
Clingy versus roamer (how far the dog prefers to be from its master, whether glued to your side or entire world tiles away)
Specifically on the courage of dogs in fights, three of the dogs I mentioned in the other post make a good example of the difference with a fight we had with a Njerp. The three dogs all attacked on command without a problem. The Njerp had a blunt weapon and started swinging at the dogs, and almost as soon as the fight started Olli was running away. Rikori stayed fighting until he was unable to stand, at which point he dragged himself away. Likewise, Sammi continued attacking until he also collapsed, at which point he tried to flee. I then stepped in and killed the Njerp (I was almost dead from a previous fight when we stumbled across the Njerp, so I was keeping well back from him). Sammi and Rikori were a mess, both with fractured shoulders, elbows, legs and chests and a bleeding fractured skull for Rik, who spent the next several hours slipping in and out of consciousness before thankfully stabilizing. Olli, when he finally showed up, had a bruised shoulder. Olli did not get fed that night.