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From the Editor in Chief
Nigel Shadbolt
University of Southampton
[email protected]
In Memoriam
I
n my last column, I mentioned work underway to frame
a particular computer science Grand Challenge. This
effort, called Memories for Life, originated in a workshop
in Edinburgh last year. The idea is to develop a research
agenda around the challenge of recording an individual’s
lifetime experience. What science and technology do we
need to build systems that store, index, and manage such
content?
An intriguing topic
This challenge has interested readers and the media alike.
I’ve been thinking why this might be and reflecting on the
research agenda that might arise. The interest might originate in the appeal of Grand Challenges themselves. The
idea is that they’ll lead to a revolutionary shift in thinking or
practice and generate enthusiastic support from scientific
communities. A good Grand Challenge should confer longterm benefits to science, industry, and society. It should
have international scope and invariably will generate interdisciplinary and collaborative research. However, although
Memories for Life might meet these criteria, I suspect that a
much simpler feature is generating the email—namely, that
this Grand Challenge appeals to the imagination.
Everyone is interested in memory. Writers, artists, scientists, and philosophers have all labored mightily on the topic.
Our essence resides in our memories. To see this, you only
have to look at individuals who have undergone neurological trauma and cannot form long-term memories. Many
have perfectly good memories up until the point of the injury or disease. Thereafter, they live in the present, perfectly
able to read a news article and a few minutes later come back
to it and read it again, totally unaware that they’ve seen it
before. This condition also is a symptom of some neurodegenerative conditions in the elderly. Many of them can
recall memories from their youth, but what happened earlier
in the day completely escapes them.
Memories are both personal and social: some are unique
to the individual, others are held in a collective recollection.
Think of your first day at school; think of what you were
doing the moment you heard about the Twin Towers. Ask
yourself, what is your first memory? Why do we remember
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so little from before age eight—a condition psychologists
call “infantile amnesia.” My own daughter, who is nine,
would engage me as a three-year-old in detailed recollections of what she had done in her nursery; she could remember in clear detail events that had happened weeks and
months before. Most of these are of the vaguest recollection
for her now; the clarity and precision of those early recollections are gone. We must have all found ourselves wondering
where our memories have gone. Are they lost, temporarily
mislaid, diminished, or overlaid? How are they structured?
Do we have one or many memory systems? How can a
smell evoke a sense of place, or a song a moment in time?
The science of memory
There’s a lot of science we can draw on here. For example, psychologists studying memory have identified multiple systems. We have working memories that support a
variety of information processing. To get to the end of a
sentence and know what it’s about, it’s important to have a
short-term memory to store the structure and sense of the
sentence’s beginning. As you read deeper into an article,
other parts of the memory system kick in while the working memory is busy with the sentence you’re reading.
Long-term memory appears to have distinct functional
capabilities. It appears to involve four types of memory
systems:
• Episodic: for example, remembering when you last
rode a bicycle
• Semantic: remembering what a bicycle is
• Procedural: remembering how to ride a bicycle
• Recognition: how to recognize an instance of a bicycle
Different brain structures are at work when these components operate, and damage can knock out one component,
leaving others intact.
Psychologists have also noted that episodic memories
are organized temporally (with respect to the person remembering) and must be remembered consciously. They’re
also susceptible to being forgotten and are highly context
dependent. So, for example, being in the same physical location as the original event can facilitate recollection. Semantic memory seems to be organized with respect to general
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knowledge and isn’t organized temporally. The objects of semantic
memory are simply known rather than consciously recollected. They
also seem to be relatively permanent—the very last memories to fail
in many age-related dementias—and are context independent.
The study of human memory has revealed much else. In a very
accessible book, The Seven Sins of Memory (Houghton Mifflin,
2001), Daniel Schacter describes a range of phenomena that clearly
put the lie to any notion of memory as analogous to file or content
retrieval in a computer. We see transience, which is the weakening or
loss of memory over time. Numerous examples exist of blocking,
where a person fails to retrieve something in his or her memory. We
frequently misattribute with respect to our memories, forgetting
when, where, who, or what. We demonstrate suggestibility, where
memories are reconstructed or reinterpreted, changing the original
recollection considerably. There are numerous examples of bias,
where a memory is misrepresented. Often we demonstrate absentmindedness—a breakdown between attention and memory. Finally,
Schacter highlights persistence, which is the inability to suppress or
remove memory—a blessing or a curse, depending on the context.
All of which demonstrates, if demonstration were needed, why
memory is not simply file retrieval. Other neuroscientists are unraveling both the locus and biomolecular basis of memory. Researchers have shown that the hippocampus is important in the representation of memories with a spatiotemporal component. Place
cells in the hippocampus of rats fire most strongly when rats pass
through familiar parts of an environment. Imaging techniques such
as functional magnetic resonance imaging are providing increasingly detailed views of the brain structures used in a variety of
memory tasks. Studies have implicated particular molecules and
receptors that appear to modify the efficacy of the connections between nerve cells. This modification appears to be an important
means by which memories are formed.
rise to substantial challenges. Given that the hardware will let us record continuous amounts of experience, how do we represent and
model the content? What sort of indexing and metadata can we use to
allow contextual retrieval? What are the ontologies for a lifetime?
How will these need to evolve and change as an individual’s experience, interests, goals, and attitudes develop? How do we summarize
experiences so as to provide a gist or précis? There’s a requirement to
encode content across different modalities—sight, sound, taste, smell,
and touch. What sorts of representations will these be?
N
o lack of challenges here, and, as I’ve argued in previous
editorials, hardware developments will create the requirement for
some sort of response to them. Storage systems such as Fujitsu’s
.8-inch, 80-Gbyte hard drives and the ever-decreasing size and
power requirements of cameras and their transmitters will mean
that individuals will increasingly be able and willing to commit
their lives to bits. Whether they should is another matter. And if a
person decides not to recode his or her own experience, what about
those who would do it for that person covertly? There are Grand
Challenges here of both a technical and social nature.
What about computers?
But does any of this inform how we might think about memory
in our computational devices? Clearly, the whole neural network
and connectionist paradigm has been inspired by the idea that concepts and events can be represented in a distributed fashion in computers. The representations are essentially weight spaces that can
be subject to decay, overwriting, attenuation, and strengthening in
ways strongly reminiscent of elements of biological memory.
Associative retrieval is also a feature of connectionist memory systems. However, it’s perhaps less clear how to represent phenomena
such as bias and reinterpretation. And if we’re to produce memory
systems that complement human memory, we need to be aware
that these processes are every bit as important as veridical recall.
In fact, you could argue that the sins of memory are actually virtues—as humans, we edit and embellish our memories to fit our
perception of ourselves and others. Forgetting might serve a range
of important purposes. Traumatic events might best be buried and
forgotten. The daily trivia of existence wouldn’t be welcome if
they re-presented themselves at every waking moment.
You could also argue that we can’t and shouldn’t seek to emulate
all facets of human memory. Instead, we should aim to provide memory augmentation systems. Certainly, this has been a more successful
approach in the past—rather than building knowledge-based systems
that emulate expert behavior, we build decision support systems that
augment problem solving. However, even a memory prosthesis gives
NOVEMBER/DECEMBER 2003
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