Blacking out vs. passing out
       Blacking out is commonly confused with passing out .  It cannot be overemphasized that these two conditions are mutually exclusive.  That is, by definition, at any given time, you cannot have one if you have the other.  A blackout is a period of amnesia during which the person is actively engaged in behaviors (e.g., walking, talking) but the brain is unable to form new memories for the events, leaving the person unable to recall the events once they are no longer intoxicated.  Consistent with the definitions used by other researchers, Goodwin et al. (1969a) defined a blackout as "amnesia for the events of any part of a drinking episode, without loss of consciousness" (p. 194).  Indeed, far from losing consciousness, the literature suggests that it is possible for individuals to experience blackouts while appearing only moderately intoxicated to the outside world.  Jennison and Johnson (1994) state, "Blackouts usually happen in a drinking setting during which the person may or may not appear to be intoxicated" (p. 24).  Further, Sweeney (1989) indicates that "...a person may drive a car and carry on a conversation in a nearly 'normal' fashion" (p. 161).
       The term passing out is less clearly defined, but is invariably used to mean either falling asleep from excessive drinking or literally drinking oneself unconscious.  Even in its most general, colloquial usage, passing out indicates the occurrence of a state that is incompatible with active behavior.  Given that blackouts tend to occur at relatively high BAC levels, particularly after rapid consumption of alcohol, it is certainly possible that an individual could experience a blackout prior to passing out.  However, the two states cannot occur simultaneously, as a person cannot be both conscious and unconscious at the same time.