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Anybody who has ever drank a lot (or been around people who do) knows about this phenomenon. Entire sections of the night can disappear from a person’s memory without a trace. A recent Lifehacker article about drinking and decision-making caught my eye, and one comment in particular claimed that the poster did not believe that blackouts exist. I decided to do a little research and re-examine what I know about the topic.
The Folk Wisdom
We learn a lot in college, though perhaps one of the more common skills this day is “how to drink.” Collectively, college students have a collection of vaguely informed knowledge on everything from exercise to alcohol that could make the most absurd wives’ tale look like a scientific analysis.
Here’s a few things that I heard about blackouts in college:
- They come in varying degrees; brown-outs being a situation where the memory will (partially) return with prompting (eg. from a friend), while a blackout is a full lack of recall (“I did WHAT last night?”)
- Hard-alcohol (spirits, as opposed to beer) leads to blackouts more readily
- Drinking on an empty stomach leads to faster intoxication, and thus it is easier to accidentally black out (you go through the stages of drunkenness faster, sometimes at an unpredictable rate)
- Each time you black out, it becomes easier to do so next time
- A propensity towards blacking out is genetic
I can say without a doubt that #1 is true from empirical evidence. Anecdotally, I also “feel” than #2-4 are also true. I had no way to form an opinion about #5, except to observe that I have friends who have never blacked out (despite breaking every other rule in this list). Of the examples I can think of, it occurs to me that more than half (at least) are of Irish descent. But, again, this is far from a scientific statement.
Blackouts are not a result unique to the consumption of alcohol. Notably, physical abuse, huger (especially in hypoglycemics or other cases of low blood sugar), other drug abuse and potentially even stress can cause blackouts.
Clearly there are a number of factors at play here; memory formation (and recall) are very complicated systems. On the high level, being unable to recall an event could be caused either because the memory failed to be recorded or because the brain cannot access the memory. In other words, it is a problem with either storage or retrieval (well, I suppose it is hypothetically possible that the memory could be erased somehow, but I do not know of any good examples of this, and functionally it would amount to a problem with retrieval).
Psychologists and Psychiatrists know that the mind can effectively block a memory from being retrieved in order to protect the psyche (for lack of a more concrete way of phrasing it). For example, multiple personality disorder is commonly caused by severe emotional trauma leading to a break in personalities within the mind. One personality often takes on a “protector” role, asserting dominance when the patient feels threatened, thereby compartmentalizing the traumatic memories away from the “normal” personalities. For more on the subject, I highly recommend the book First Person Plural : My Life As a Multiple, written by a man who developed multiple personality disorder late in life and went on to get the condition under control, study the subject, earn his degree in psychology.
But I digress. In the case of alcohol (or drug-related) blackouts, we can essentially narrow down the problem to one which occurs while under the influence. This seems to indicate a problem in storage (not in retrieval).
Indeed, a neuroscience class I took in college as well as this research paper confirm that “mechanisms underlying alcohol-induced memory impairments include disruption of activity in the hippocampus.” The hippocampus, unsurprisingly, is the region of the brain most associated with the storage and retrieval of long-term memories. I tend to think of it like the tip (head) of the hard drive – it does not actually contain the information, but rather is the mechanism that reads & writes the information.
I also came across this study in support of the genetic component of blackouts.
As I learned more about human memory, I started watching people who were heavily intoxicated a bit more closely (they had no idea they were becoming a part of my experiments!)
What I noticed was, in extreme cases, the blackout effect is immediate and predictable. If you have studied human memory formation, you know there are fundamentally 3 types of declarative memory: long-term, short-term and working memory. Sure enough, with the hippocampus impaired, people experiencing a blackout immediately have no long-term memory.
Here’s how to test it: someone experiencing a full-blown blackout will only have access to short term memory, meaning that they cannot effectively recall things that happened some time ago (but also in the blackout). The time an item can remain in short term memory varies, but the practical cutoff point is 10 minutes on the high end. For example, if you’re bar hopping with friends, you could prompt your friend about something that happened at the last bar you were at. If he’s experiencing a blackout and the event happened more than 10 minutes ago, he’ll look at you with a confused look on his face. Once you have seen this once or twice, it starts jumping out at you.
Anecdotally, I wonder about the component of emotional memories. I have frequently noticed that even someone in blackout will be affected by an emotional event consistently. For example, a blacked-out club-goer who loses her purse might remain upset/sad/angry throughout the course of the night after realizing she lost the bag. Emotional memories are not declarative, meaning they work with different mechanisms. In fact, the “emotional part of the brain” exists on a “lower level” (to vastly over-simplify the reptilian, mammalian and neo-cortex parts of the brain).
Interestingly, I have noticed cases where even a blacked out person can recall the actual emotional event. To continue the above example, the girl might keep saying “ugh, I can’t believe I lost my purse!” through the night, even though she does not remember anything for hours before or after the event. I would suspect that this may have to do with the release of cortisol and other hormones which cause us to remember emotional/traumatic events exceptionally well. In other words, the brain’s natural response is to “beef up” recall during an emotional event, which temporarily circumvents the blackout. Again, though, these last bits are purely speculative. For more on emotional memories, Blink by Malcolm Gladwell is an entertaining read.
Do you have anything to add? Anecdotes or personal experiences? Let me know below!