Stuttering usually occurs on the initial sound or syllable of a word, in the first word of a sentence, on accented syllables, and on "content" words. "Content" words carry the meaning of a sentence, which is why when listeners guess what a stutterer is trying to say, they often guess wrong.

Stuttering increases when saying one's name, speaking on the telephone, speaking to an authority figure, or speaking to an audience.

Stuttering decreases when saying a phrase repeatedly, speaking in chorus with another person, when speaking alone or to animals, when singing, using a lower pitch, using a different accent, using electronic anti-stuttering devices, and when crawling on all fours!

Some stutterers can read fluently, while others can't. Some stutterers are fluent when they try to stutter, others stutter more.

Stutterers report having "good days" and "bad days", possibly due to changing dopamine levels in their brains due to diet and other factors.

Some of these effects are psychologically-conditioned, such as speaking to authority figures. Other effects are physiological, such as lowering vocal pitch, or speaking in chorus with another person.