This article is from the Mastiffs Breed FAQ, by mmcbee@access.mountain.net (Mike McBee) with numerous contributions by others.
Mastiffs ARE protective. However, many people do not
understand the difference between protection and aggression.
If a dog growls when there is no danger, that is aggression,
NOT protection. A protective dog has the judgment to see when
there is a real risk of danger, and therefore, if you have a
TRULY protective dog, you may never know it till you ARE in
danger.
The protective instinct is shown in subtle ways, such as the
Mastiff tending to stand between their person and a stranger.
Many people who have kids discover that they can't spank a
kid in front of the Mastiff -- it looks worried and gets in
between the parent and child! Couples who sometimes
play-wrestle together have reported their Mastiff trying to
stop them for fear it is a fight.
 
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