Our list already includes many memory-related ‘things’ but must also include recent findings from differential-psychology (individual-differences) studies of working-memory capacity, as measured by complex-span tasks like reading span, operation span, symmetry span, and so forth. In particular, Engle and collaborators have shown, by comparing people who are relatively high vs low in WMC, that the capacity for (not the limits of) WM
-principally involves controlled or executive attention for maintaining and manipulating information;
-uses (but isn’t) STM storage itself;
-is highly related to fluid intelligence (reasoning), not because they are the same thing, but because the latter involves another controlled-attention operation: disengagement (the opposite of maintenance); and (among other things);
-may or may not be correlated with individual differences in processing speed, depending on how processing speed is measured (e.g., whether or not measured with tasks that require controlled attention).
This latter point is important, as individual differences in processing speed typically correlate well with measures of general intelligence—accounting for as much as 80% of the variance in some studies. Developmental improvements in processing speed are associated with language learning and other cognitive outcomes. Processing speed differences have been implicated in a wide range of developmental disabilities and health-related outcomes as well. Even more critically, Timothy Salthouse showed that declines in processing speed account for most of the age-related cognitive declines in memory, fluency, attention, and inhibition that are seen in older adults.