Cognition

Some 60,000 years ago, at the end of an ice age, there were humans over much of the world. They all encoded their world into episodes and used tools to act upon it. After the ice age ended, the descendants of one family who lived in east central Africa began to migrate north, and then west into Europe and east into Asia. Wherever they went, the people who already lived there went extinct (there was a small amount of interbreeding in Europe). Everyone in the world today is therefore descended from this one family. Clearly, this family had some enormous advantage that allowed them to conquer the world. One likely possibility is the invention of human language.

The fundamental unit of memory is the episode, in which a voluntary action to a target in a specific context, and its result, are encoded. This is a polymodal representation involving more than one sensory modality and more than one representation. So, when a visual target is matched to a representation in memory, the response is the activation of an entire episode that includes a previous action to the target in a specific context and its consequence. This knowledge of the previous encounter with the target may be used to guide behavior during the current event. As mentioned in Chapter 2, this kind of knowledge is called declarative knowledge. Declarative knowledge is of two kinds: semantic knowledge and episodic knowledge. Semantic knowledge is knowledge of what something is, and episodic knowledge is knowledge of when it has been encountered previously. Episodic knowledge will be discussed in Chapter 12. We begin the discussion of semantic knowledge here. The representation of semantic knowledge is commonly called semantic memory.

The components of an episode – the target, the action, etc. – are associated with verbal and written labels called words. When a visual target is matched to a representation in memory, the response to it includes the word naming it as well as the episode. Conversely, when a word is heard, the episode whose component it names is activated. Consequently, when people encounter or hear about a target, everything they know about it immediately becomes available to guide their action.

Essential as they are, individual words are limited in how much information they communicate. To let someone know what you wish to do or what you have done, entire sentences are necessary.