This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
About 30 years ago I saw my first Jim Jarmusch movie, Stranger than Paradise at the Detroit Film Theatre, a popular site for indie film screening situated in the Detroit Institute of Arts. It is fitting that Jarmusch's latest film, Only Lovers Left Alive, staring Tom Hiddleston and Tilda Swinton as Adam and Eve, takes place in Motor City.
Being a film about vampires set in city where I once lived, it got me to thinking about what vampires can teach us about the workings of memory. Vampires have two features of interest to memory theorists. First, to the extent that they avoid angry mobs, they are immortal, allowing them to accumulate life experiences indefinitely. Second, they are immune to the effects of aging. This is of interest because, in the living, the deleterious effects of long periods of time on memory are inextricably confounded with the effects of aging on brain structure and function. A vampire’s memory would allow us to disentangle the effects of time and aging.
I must admit that I have failed to attract even a single vampire to my laboratory for testing, but in the absence of data, allow me to speculate on how your friendly neighborhood vampire might process memories of events at a specific time or place, beginning with the issue of immortality.
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Episodic Memory
If you lived forever, would you remember everything that happened to you? The answer is no. Memory decays exponentially over time. In the Figure below, the horizontal axis represents time, starting from the present on the right, going exponentially into the past to the left as the years shrink and collapse upon themselves. The vertical axis represents the percentage of events accessible to recall, also plotted as an exponential function. While you may recall nearly everything that happened today, after three days, this goes down to 10 percent for most people. A month from now, we would be hard pressed recall more than 1 percent of today’s events. After a year, a tenth of 1 percent and so on.
With a couple of exceptions, this function is monotonic, meaning that the relationship between time and forgetting is constant in perpetuity. A normal 85-year-old mortal can recall but a scintilla (about 0.003 percent) of daily life events from his or her primary school years. Extrapolating this to a 1,000-year-old vampire, the figure would be 0.0002 percent. This is not necessarily a bad thing; forgetting is a normal process important the formation of new memories. As psychologist Théodule-Armand Ribot stated in 1882 “Without the total obliteration of an immense number of states of consciousness, and the momentary repression of many more, recollection would be impossible.” For both mortals and vampires, the most useful memories in terms of daily activities (say remembering where you parked the car or where to find fresh blood) are the most recent ones.
The first exception to the monotonic forgetting function is the period of infantile amnesia from birth to around age four, where few to no events are retained into the adult years (for a recent neurobiological account of infantile amnesia focusing on hippocampal neurogenesis, click here). The second is the “reminiscence bump,” which refers to the period peaking around age 20 during which events and the cultural milieu are bound up with the formation of one’s identity, gracing that period with enhanced recall and preference.
Events occurring during the reminiscence bump survive in memory because they are personally significant and emotional. These same events are also repeatedly recalled and reviewed in memory, enhancing their status in our autobiographies. Vampires were once young, after all, so they too are entitled to a reminiscence bump. There is no reason to think that a vampire’s first kiss would fade from memory even after 1,000 years. Thus vampires’ early adulthood events would retain their special status in memory, as is the case for mortals.
The figure above shows the percentage of events recalled, but what about the quality or vividness of those memories? In 2002, my group discovered that with age, mortals recall fewer episodic (specific) details (e.g., “it was a shiny red Mustang”) and more non-specific details or commentary (e.g., “they don’t make Mustangs like they used to!”). This phenomenon may be due to an age-related failure to suppress off-task thoughts. While vampires’ detailed recall may suffer from the passage of time, their stories (such as Adam’s personal reminiscences of Lord Byron in Only Lovers Left Alive), immune to the effects of aging, would be crisp and free of clutter.
Non-episodic memory
Memory of skills, habits and expertise are not subject to the same decay as the memory of episodes and events. Yet when it comes to self-improvement, the inevitability of death forces certain choices. Although I would like to pick up a new language or perfect my tempura technique, there are other priorities and there is only so much time.
Vampires are confined to evening hours, but otherwise have a lot of time to work with. Whereas aging shifts mortals’ focus towards present well-being and “generativity” (the desire to nurture younger generations) and away from long-term goals, no such effect is expected in vampires. Although some squander their immortality (there is one such example in Only Lovers Left Alive), vampires are generally a cultured, even uppity bunch that can hold their own in any conversation. In Only Lovers Left Alive, when packing for a trip, Eve selects books in several languages.
With aging, mortals acquire more knowledge and wisdom, yet processing speed and physical capacities decline, leading to the aphorism that youth is wasted on the young. For vampires, there is no theoretical limit on the number of skills that could be acquired to a reasonable level of competence, aside from pastimes that require being outdoors in the daylight or the use of a mirror. Vampires have the best of both worlds: whereas mortals are wise and slow, vampires are wise and fast. The tricky part would be to maintain these learned skills. Having taken piano lessons in the Elizabethan era would not be of much use today without regular practice. The following advice, amalgamated from cognitive neuroscience research, is for readers who are vampires and want to maximize their self-improvement:
Choose two or three things from different categories, such as physical skills, artistic talents, and intellectual pursuits (e.g., billiards, playing the banjo, and Greek literature, respectively). The variety of tasks will keep up your motivation and support training-induced neuroplasticity through strengthening of complementary brain systems.
Spaced or distributed practice is better than massed practice, so cycle your training for each task across days, allowing for a day or two of rest before returning to each task.
Take one or two days a week to reinforce and maintain skills that you have already mastered.
Get a good day’s sleep, for sleep is essential for consolidation of learned skills.
Finally, choose skills with staying power. You’d be sorry if you had chosen macramé in the 70s just because it was hot.
The complexity of the human brain, with 100 billion neurons and 100 trillion connections, is beyond comprehension, at least with current methods. Given sufficient time, the amount of information that could be absorbed through the neuroplastic sculpting of these connections is limitless. The benefits of greater exposure and experience enjoyed by mortals are offset by the liabilities of age-related brain changes. Although vampires are subject to the same forgetting function as mortals, they illustrate the brain’s capacities for learning and memory that can only be seen in the absence of brain aging and finite temporal horizons.
Further reading
Levine, B., Svoboda, E., Hay, J., Winocur, G., & Moscovitch, M. (2002). Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychology and Aging, 17, 677-689.
Rubin, D. C. and M. D. Schulkind (1997). "The distribution of autobiographical memories across the lifespan." Mem Cognit 25(6): 859-866.