I've an odd feeling I've read this before
- From: "Lance" <lachenicht@xxxxxxxxxx>
- Date: 17 Aug 2005 04:50:47 -0700
Looking at Déjà Vu for the First Time
False-familiarity experiences may fit a plausible framework
By Alan S. Brown
As a culture, we have difficulty letting go of the outdated notion that
memory is a reliable tape recorder. Even memories for important events,
such as eyewitness accounts of crimes, are usually riddled with
imperfections, distortions, and lacunae. Perhaps our irrational faith
in memory's accuracy stems from our personal investment in remembering
precisely where we parked the car, or our terror that memory's
imperfections signal the early warning signs of senility. Memory
researchers are increasingly breaking free from this mind set to
examine memory difficulties as a vehicle to develop a better
understanding of normal memory function.1 Solid scientific research on
phenomena such as déjà vu is now beginning to emerge for the first
time.
When memory fails, we are frustrated, but when memory appears to make
up things, we may become even more concerned. A number of recent
demonstrations have shown how easy it is to implant "memories" of
things that never occurred. These false memories can range from the
mundane, such as recalling a nonexistent word from a list,2 to complex
experiences, such as getting lost in a mall as a child.3 Our memories
also appear to be fabricating experiences during déjà vu, where our
feelings of familiarity simply should not exist. Viewed from another
perspective, déjà vu results from a sudden collision between our
objective and subjective evaluations of familiarity: We are convinced
that the present event is new, but are gripped by the overwhelming
sense that we have lived it before.
What causes this illusion of positive recognition? Unfortunately,
déjà vu experiences routinely lack clues pointing to any empirically
verifiable causes, so prior speculation about the experience has
spanned a wide spectrum, including past lives, precognition, brain
pathology, and schizophrenia. But increased research on the brain and
cognition has provided four scientifically plausible frameworks for
understanding how déjà vu works. The experience could be a simple
neuronal misfire, a result of asynchronous message processing, the
sudden recognition of something otherwise overlooked, or a misplaced
association between an object remembered and a new experience. Of late,
we have developed better tools to evaluate these frameworks, and the
findings may offer insight into how memory works, and why, sometimes,
it doesn't.
A RANDOM FIRE
Suppose a déjà vu is nothing more than a spontaneous misfiring in the
brain that is unconnected to any external experience? We think little
about a muscle twitch, but when this same sort of neurological spasm
causes a disruption in our higher cognitive centers, we are much more
disturbed. Speculation about this electrical problem in the brain began
with the observation that some patients with epilepsy experience déjà
vu during the preseizure aura. Such patients nearly always have a
seizure focus in the hippocampus or amygdala of the temporal lobe, a
structure that handles familiarity assessments and information
encoding. Thus, it seems reasonable to speculate that a random
electrical discharge in this area of the brain could create an unbidden
sense of familiarity that is not elicited by the present experience,
leading to a déjà vu.
Occasionally, individuals report constant déjà vu due to illness,
injury, or traumatic stress. An extended EEG recording with such
individuals would help to track down the physiology of déjà vu. Also,
some prescription medications have been shown to increase déjà vu
frequency in anecdotal reports, and controlled investigation of such
medications may help identify neurotransmitter alterations related to
déjà vu.
OUT OF SYNC
Information traveling from sensory organs to higher cortical processing
centers appears to route through several tracks. That is, multiple
copies race through the brain to a final destination where the sensory
impressions are merged into a unitary experience. If one of these two
tracks gets briefly impeded, or slowed down, by a minor synaptic
mishap, the brain could experience two separate copies of the same
sensory experience rather than one integrated message. Given the rarity
of such an event, the brain may not have the capacity to identify that
the duplicate message arrived only milliseconds rather than months
earlier, and déjà vu results. We are investigating this possibility
through a split-screen presentation of visual information. An identical
image is presented in varying degrees (milliseconds) of asynchrony to
the right and left visual fields. We predict that when presented with a
novel stimulus, a slight separation between the presentations of the
two images may elicit a false sense of familiarity.
IN FRONT OF YOUR NOSE
Have you ever looked for your glasses and they are right on your desk?
We routinely fail to fully process the objects and people around us,
causing us often to miss things that are obvious. Nevertheless, this
information still registers in our memories.4 For instance, research on
inattentional blindness demonstrates that we often overlook an
unanticipated stimulus object when it accompanies another object that
we are looking for.5 Even when we deny that this item was shown to us,
our altered response to a subsequent encounter with this same stimulus
demonstrates that it made an imprint on memory. In short, the brain is
primed to respond to this stimulus even though we don't consciously
remember experiencing it.
Taking this lab result into the real world, when we are lost in a phone
conversation or our own thoughts, the sights and sounds around us make
an impression on the brain, even if not on our conscious awareness.
Moments later when we hang up the phone or snap out of our inner world,
we are struck by the familiarity of what we are now looking at with
full awareness. The subconscious brain worked to perfection; it sends a
recognition alert that the imperfect conscious brain misinterprets as
false familiarity. Several laboratory studies over the past decade have
verified the possibility that a fleeting glance moments before can
trigger a reaction that resembles déjà vu.6,7
PULLED FROM MEMORY'S ATTIC
What we attend to gets stored in the brain, but much of what we don't
attend to also resides somewhere in memory. Some of the many sights and
sounds that we encounter each day may connect to these hidden memory
fragments of experiences from months or years ago, and this conjunction
can trigger a rush of familiarity, positive affect, or even anxiety,
that we label as déjà vu.8 For example, the phrase that a friend just
uttered duplicates the prose from a novel read last year; the lamp in
the corner of a restaurant lounge is identical to one in your sister's
living room; the mannerisms of a person you just met duplicate those of
your elementary school principal. Your implicit memory correctly
signals "oldness," but you are unable to connect this with a specific
memory. In the absence of an obvious connection, you are thrown into a
state of familiarity without reference, and generalize the sensation to
the entire setting.
We are currently working on several research projects guided by this
notion. Students get a superficial glance at a series of pictures as
they identify the location of a small "+" embedded somewhere on each
one. A week later, they return to the lab to view these old scenes
mixed in with new ones, and indicate whether they have actually visited
the location shown. Students are occasionally fooled into thinking that
they have been to the previously glanced location, evoking a false
sense of familiarity that resembles déjà vu.
As the above interpretations clearly illustrate, advances in our
understanding of how the brain works allow us to put déjà vu on a
solidly scientific basis in a way that was not possible several decades
ago. Even the strange subjective impressions that many feel during
déjà vu, such as precognition and dream connections, can be explained
within an empirical framework.6,7 I believe that through the memory
illusion of déjà vu, the brain is sending us clues about how it
routinely processes and interprets our experiences. Déjà vu may serve
as a rich mental mother lode of ideas that can have broad cognitive
implication. This evanescent cognitive imperfection can tell us much
about normal memory function; we just need to learn how to listen more
carefully.
Alan S. Brown, a professor of psychology at Southern Methodist
University, studies human memory. He is the author of The Déjà Vu
Experience (Psychology Press, 2004).
References
1. HL Roediger "Memory illusions," J Mem Lang 1996, 35: 76-100.
2. HL Rories "Remembering words not presented in lists," J Exp Psychol
Learn 1995, 21: 803-14.
3. EF Loftus, JE Pickrell "The formation of false memories," Psychiat
Ann 1995, 25: 720-5.
4. LL Jacoby, K Whitehouse "An illusion of memory: False recognition
influenced by unconscious perception," J Exp Psychol Gen 1989, 118:
126-35.
5. A Mack, I Rock Inattentional Blindness Cambridge, Mass.: MIT Press
1998.
6. AS Brown "A review of the déjà vu experience," Psychol Bull 2003,
129: 394-413.
7. AS Brown The Déjà Vu Experience New York: Psychology Press 2004.
8. JG Seamon et al, "Affective discrimination of stimuli that are not
recognized: II. Effect of delay between study and test," B Psychonomic
Soc 1983, 21: 187-9.
http://www.the-scientist.com/2005/1/31/20/1
.
- Prev by Date: Re: Cave Thinkers
- Next by Date: Re: consciousness
- Previous by thread: Cave Thinkers
- Next by thread: Epigenetics
- Index(es):
Relevant Pages
|
Loading
