Your brain ignores dubbed voices that lag by 200 milliseconds
When audio and video fall out of sync, the human brain stops processing speech as a single event and begins treating the eyes and ears as two competing witnesses.
The human brain is remarkably forgiving of slow sound, a biological legacy of the fact that light travels faster than noise in the physical world. However, this patience has a hard limit at roughly one-fifth of a second. This threshold is rooted in the McGurk effect, a perceptual phenomenon where your brain prioritizes what it sees over what it hears. If a character's lips form the shape for a 'ba' sound while the audio plays a 'ga,' your mind will often hallucinate a middle ground like 'da.' Once the delay exceeds 200 milliseconds, this subconscious fusion breaks entirely, and the illusion of a living, breathing speaker dissolves into a distracting technical error.