Most members of the breed are not easily spooked, enjoy trail and arena riding and, with proper training, can become excellent horses for children and adults alike. You could, for example, find a 13.2 hand cutting horse that is as agile as a cat or a 17.2 hand hunter horse that has a beautifully elegant long trot and graceful form over 4 foot fences.
Because there are many components, there is a high amount of variability within any breed, including the Quarter Horse. Breeding and pedigree do have a big influence on the temperament of a quarter horse.
While all QuarterHorses can be very versatile, each equestrian discipline lends itself to horses who possess specific traits. Cutting cows and keeping them separated from the herd can be hard, taxing work.
Cutting horses are also, typically, hotter or more energetic than most QuarterHorses used for recreational riding. These types of horses have made their mark in Hunt Seat Equitation and Western Pleasure classes.
I once knew an Appendix Quarter Horse, bred specifically for racing, that had no desire to run. Proper training, both on the ground and in the saddle, can give your horse a great set of building blocks from which it can make decisions.
It is crucial that the training process teach a horse how to make the right decisions in unknown situations. A horse who has learned to stop and think in a suddenly fearful or unknown situation is less likely to injure its rider than one who turns and runs because that is the only thing he knows how to do.
Similarly, adequate groundwork can teach a horse to trust when you ask him to go forward and stop when you need him to. If he is ever in a sticky situation or having to walk through an unknown place the horse is better able to respond to your commands because he has the training and reinforcement to trust what you ask of him.
Having acknowledged that pedigree is only one factor in a Quarter Horse’s temperament we can then look constructively at different personality traits that certain lines of QuarterHorses are “known” for. I personally had the pleasure of riding a bay roan Hancock bred mare for years who was one of the nicest, laid back, easy-going horses you’d ever meet.
On the other hand, I knew a Hancock gelding that would “break in two” or start bucking wildly, for seemingly no reason at all. Despite this “habit” that Hancock bred QuarterHorses are known for, their nice heads, good balance, toughness, and soundness make them great ranch horses and well-liked among ranchers.
Their temperaments are touted for being naturally calm, cool and collected seemingly straight from the womb. These two stallions produce awesome western pleasure and hunter horses (and their babies compete in many other disciplines too).
It seems that horses from lines bred primarily for rail work seem to be calmer and easier than horses bred for active work like cutting and reining. In fact, when you can, riding or handling a horse on multiple days in as many environments as possible will give you a good look at what his true temperament might be.