Knowledge modelling, part 3

MEMORY AND KNOWLEDGE

Another key feature of the human brain is that it uses different types of memory, long term memory vs working memory which have very different characteristics from each other, summarized in the table on the next page.

Long term memory has huge capacity and can last a lifetime. Working memory (sometimes referred to as short term memory – there’s debate about the details in the psychological literature) has a very small capacity, of about seven items (plus or minus two); it also has a very short duration of a few seconds. Information from working memory is often lost, but can also be consolidated into long term memory.

Working memory
Working memory functions as a mental scratchpad for information that we only need to retain briefly. However, its limited capacity has serious implications for performing complex mental operations without using paper or similar recording tools.

Suppose, for instance, you’re trying to multiply 14 by 17 in your head. Your brain needs to remember the numbers 14 and 17. It then needs to perform a series of calculations e.g. multiplying 14 by 10, and 14 by 7, and add the results from these multiplications; each operation takes up more working memory capacity. This rapidly overloads working memory. The consequence is that we have very limited ability to perform calculations, or formal logic processes, in our heads.

Long term memory
There are two main types of long term memory; explicit memory that can be readily, consciously recalled; and implicit memory that can be acquired and used without our being aware of its content.

Explicit memory takes two forms. Episodic memory involves past events and their context e.g. the office party last Christmas. A ‘flashbulb’ memory is an especially vivid episodic memory e.g. the office manager falling downstairs after the party. Semantic memory involves information about things (e.g. facts about the office staff). Explicit memory is sometimes referred to as declarative memory – memory that can be described in words.

Implicit memory often takes the form of procedural memory; being able to perform a particular task, but unable to describe the steps involved without observing them e.g. making a cup of tea. It can also take the form of pattern matching e.g. recognising a familiar face without being able to describe or draw it accurately.