We say: Four times that if it's Sex and the City and you're male.
Researches at the University of Tokyo have found that the brain pauses for up to 450 milliseconds with every blink, meaning we miss up to 6 seconds of visual info for every minute—or about 15 minutes for a 150 minute film.
In tracking the eye movements of volunteers, the team also found that moviegoers can sometimes begin to blink in unison; an external manifestation of sharing a common experience. Apparently, the synchronized blinks seem to happen at "non-critical" points, like after an explosion, or whenever Megan Fox is off screen. [University of Tokyo via New Scientist]