What causes a stutter? Well for some, they're genetically pre-disposed to develop one, for others it's caused by stroke or head trauma later in life and for others it's caused by some traumatic event such as a dog attack, car accident, snake bite etc... Regardless of the cause, the speech disorder known as stuttering is classified as a neurophysiological condition because there exists structural differences in certain speech areas of the brain which disrupts the activation of muscles during normal speech function. I'm a part of the first subset of stutterers. So it runs in my family. The oldest member who stutters is my grandmother on my fathers side. My grandfather was not a stutters. My dad stutters and his full brothers stutter. But his half brothers do not stutter. So it seems whether it gets based on also depends the genes of the other parent. Then you have the colloquial term known as "stuttering" that non-stutterers use. It's used to describe when someone startes to trip over their words when they're nervous, anxious or under suffer some emotional disturbance. When you tell people you stutter, they're gonna think your using this term. But you're really talking about the speech disorder known as stuttering.