Memory intelligence tests evaluate a person’s ability to store items and information in the brain, and how well the person can recall said information or items when necessary.
These tests are designed to evaluate the Working Memory (WM) capacity. This type of memory refers to the brain's capacity to hold information temporarily1 to be used in a short span of time to support logical reasoning and/or decision-making processes2.
The WM has become central in theories of Psychometric intelligence (intelligence that can be assessed using a test) and it distinguishes contents (verbal, numerical, spatial) and operations (storage and processing)3. Although WM is often mistaken by short-term memory, the big difference is that WM is short-term memory plus the so-called controlled attention ability (the attentional capacity for performing controlled processing or sustaining focus on task-relevant information in the face of interfering or distracting stimuli); however, both forms of memory are good predictors of intelligence4.
Thus, there seems to be a robust correlation between fluid intelligence (the unlearnt cognitive skill of thinking and reasoning abstractly) and the number of items and information that a person’s WM can hold5. Research has also been showing that there is a strong correlation between WM and intelligence as assessed by tests, which supports its validity as a key cognitive resource6.
1 Miyake, A.; Shah, P., eds. (1999). Models of working memory. Mechanisms of active maintenance and executive control. Cambridge University Press. ISBN 0-521-58325-X.
2 Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 13: Higher Cognitive Function and Behavioral Control". In Sydor A, Brown RY (eds.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. pp. 313–321. ISBN 978-0-07-148127-4.
3 Colom, R., Flores-Mendonza, C. & Rebollo, I. (2003). Working memory and intelligence. Personality and Individual Differences 34(1) 33-39.
4 Colom, Flores-Mendonza & Rebollo, 2003
5 Fukuda, K., Vogel, E., Mayr, U., & Awh, E. (2010). Quantity, not quality: the relationship between fluid intelligence and working memory capacity. Psychonomic bulletin & review, 17(5), 673–679. https://doi.org/10.3758/17.5.673
6 Colom, Flores-Mendonza & Rebollo, 2003