[Added April 2012]
In his book “Thinking fast and slow” the Nobel prize winner Kahneman introduces
two fictitious characters “System 1” and “System2” to better explain how our brain works. These two characters can also better explain how our memory works.
System 2 is our slow, deliberate, analytical and consciously effortful mode of reasoning about the world that we apply when we try to compute for example
12×37 . It uses memory like a computer .
System 1, by contrast, is our fast, automatic, intuitive and unconscious mode of thinking. This is the reasoning that will make you jump
on the side walk when you hear a klaxon of an approaching car. And you discover
that this jump has saved your life. Its main purpose is to scan continuously the
environment in search of signs of danger. And when it finds something strange to produce an immediate reaction that saves us. For this reason I call System 1 the “guardian angel in our brain”.
System 1 uses memory in a peculiar way. It has two main problems to do its work:
- The analysis must be fast, so it activates continuously all neuronal pathways connected with what our senses are detecting. This activation (associative memory) brings as much as possible to memory to help to check
that everything is ok. One of the results of this brain activity is the phenomenon of priming. The study of priming has shown that this activation is
done in parallel on all words, objects and actions connected with what we are
sensing (Strange odour in kitchen, gas, open the window, close the oven ….)
- System 1 has also the need to delete quickly some of the activated ideas
that we don’t need any more in order not to overcharge our brain with unwanted stuff. This is done in an elegant and efficient way. This can be seen following
System 1 as we walk in our house. In order to check that there is nothing strange it must load a map of the whole house in our memory to compare what we
see with what we remember. This can be a lot of information but it seems that
it is loaded in parts room by room. When we pass a door the information about the room behind us is replaced with the information about the new room.
This works so well that sometimes when we arrive at the refrigerator we have
completely forgotten what we wanted.
[Added August 2005]
It is by now a well known phenomenon that the same information inaccessible to
explicit (conscious) memory, may be accessible to implicit (unconscious) memory.
You can literally see something without knowing that you are seeing it.
This has some fascinating consequences. For example, I use a list of images
connected to the numbers 1,2,3,… to remember things. So, for each number
I remember an image. But remembering (becoming conscient of ) the image
usually requires some time (from a few seconds to a few minutes). It is
very well possible that during this interval of time my implicit memory has
already recollected the image. By using some adequate strategy, I can try
to use this implicit knowledge to improve my conscious recollection.
This tacit knowledge is connected to the amygdala and to the fast system
that helps us react quickly to dangerous situations. It perceives words and
numbers as global patterns and its main purpose is to decide if they
are dangerous or neutral.
[Added March 2000]
Does the sense of smell improve learning?The other day I had the following
experience. From time to time I do “experiments” on memory by learning a
list of ten items. If I start in the evening , it will
take usually a few rehearsals and for the following morning the list is perfectly
memorised. This time, when I was starting the exercise, going through the list
for the first time, something happened. An electrical appliance misbehaviour produced a smoke with a pungent scent of melting plastic. The problem was quickly
fixed but the smell was still present after many hours. I discovered also
that my learning of the list was a lot faster and I could use, the following
morning, the smell to recall it!
Initial detection of odours occurs in the nose in the olfactory epithelium. The epithelium contains millions of odour molecule specific neurons that
make direct physical contact between the external world and the brain. When a certain odor is detected it causes certain neurons to fire in the olfactory bulb
. The olfactory bulb then sends a signal to the olfactory
cortex and then on to the Limbic system for further processing and memory recall. The information goes to the thalamus (part of the Limbic system) but also
,in case of smell and taste, to the amygdala and hippocampus(also part of the
Limbic system). This gives smell (and taste) powerful memory stimulating properties that can explain what I experienced.The Limbic system is referred as the
“seat of emotion” and is basically an information storing and processing system.The hippocampus ,for example, serves to recall simple, short-term memories stimulated by sensory input.These memories are spatial. The amygdala can ,instead,
evoke memories connected to emotion.In fact, removal of hippocampus will produce
short term memory failures. Removal of amygdala will produce emotionless aggressive behaviour in monkeys.So,it seems,that by using some smell during
learning, we are in fact storing our memories using still another track. This
will improve both the process of learning and recall.
Here is an interesting document on the subject.