Knowing that and knowing how
Dichotomy in long-term memory?
With regard to the long-term memory of the human being it has always been assumed that the following systems operate independently of each other (see also here):
A. Explicit (conscious) memory or declarative memory
This is memory of consciously accessible knowledge of facts. Examples include knowledge of your autobiography (episodic memory), or the knowledge that the Netherlands is in Europe (semantic memory).
B. Implicit (unconscious) memory
This portion of long-term memory is not consciously accessible and consists of skills, habits, and conditioned (learned) responses, which can be reflected by the reception of sensory information through hearing, smell, sight, taste and touch. One example is the ability to cycle or to use language.
In the USA it has recently been discovered that this division has to be placed into question by a study of a woman (Lonni Sue Johnson) with amnesia. She suffers memory loss due to a viral encephalitis that destroyed her hippocampus. The hippocampus is the brain area which is near the amygdala. It is the part of the brains that creates new memories and allows us to pick up old memories.
Lonni Sue cannot remember anything of her life before her illness. For example, she does not know that she has been married.
She also does not remember that she was a musician, that she liked to paint and that she was an amateur aviator.
However, when asked how to prepare a color palette she is able to tell exactly how to do it. When asked for the steps needed to prevent an airplane to shut down she knows exactly. Also a question about how to deal with a stringed musical instrument she answered in detail.
According to Barbara Landau, professor of cognitive sciences at Johns Hopkins, this contradicts the assumption that knowing how something should be done is not declarative knowledge. The sharp distinction between "knowing that" and "knowing how" will consequently cease to apply.