Working Memory and Fluid Intelligence

What is Working Memory?

Working memory is an idea developed by cognitive scientists to describe how people are able to hold information relevant to a particular task in their mind, while having to simultaneously process information relating to other tasks and contend with additional distracting information.

Many fundamental cognitive abilities including; reading, reasoning, and problem solving all require input from working memory in order to function.

The relevant information is held in an accessible state, where you can continue to use and manipulate it. However because it must be continually held in this state it also has a limited capacity. Put another way; there is only so much information your mind can hold onto at one time, this limit is your Working Memory Capacity.

Working Memory and Fluid Intelligence

Throughout the 1990s many cognitive scientists believed that Working Memory Capacity and General Intelligence (g) were one and the same thing. Studies such as ‘Reasoning ability is (little more than) working-memory’, published in the journal ‘Intelligence’ by Kyllonen and Christal showed correlations between Working Memory and reasoning ability of between 80% and 90%. These and other similar results led most working in the field to conclude that even if working memory was not all there was to intelligence it was certainly the single most important factor.

What is Fluid Intelligence?

Along with Crystalized Intelligence, Fluid Intelligence is one of the two key factors which contribute to General Intelligence according to the Cattell & Spearman model of Intelligence. You can read more about the different theories of intelligence in the post What is Intelligence?

Most of the research that demonstrates the link between Working Memory and Intelligence has focused on testing reasoning abilities rather than acquired knowledge. Therefore it is actually a link between Working Memory and Fluid Intelligence that was being shown.

This aligns well with our common sense, when we are trying to measure intelligence we aren’t interested in pre-prepared strategies or relevant things we may just happen to know, but rather with how we cope with novel, unfamiliar problems.

More recent studies and analysis such as that done by Kane, Hambrick and Conway; ‘Working memory capacity and fluid intelligence are strongly related constructs’, have shown the original estimates of 80-90% correlations to be slightly over-optimistic.

When a battery of both simple and complex span working memory capacity tasks are included, Working Memory Capacity appears to accounts for around half of the variation in different individuals Fluid Intelligence.