Following the general review of the models and theories of WM in Chapter 2, in this chapter I discuss the measures and assessment procedures for WM currently available in cognitive psychology. The chapter is organized into five sections. The first describes the storage-only versions of WM span tasks that are often adopted by European-based cognitive psychologists. The second section then reviews the more complex storage-plus-processing versions of WM span tasks that are usually implemented by their North American counterparts. In the following section I describe the theoretical debates surrounding these WM measures. I then explore some of the methodological issues besetting these measures in the fourth section. The summary section then concludes the chapter by pointing out how the research in cognitive psychology can be expanded to shed light on implementing WM span tasks in more practical research areas such as academic learning.

The Simple Memory Span Tasks

Among the different WM components (as conceived in Baddeley's model reviewed in Chapter 2), the phonological component (hereafter referred to as PWM; or the phonological loop as originally conceived by Baddeley and colleagues) is the most widely researched by European-based cognitive psychologists (Baddeley, 2012, 2015), so much so that it sometimes appears synonymous with their conception of the whole WM construct. Given the domain-specific functions of WM in temporarily storing and rehearsing sound-based materials, most of the WM researchers adopting this paradigm have focused on the relationship between PWM and language acquisition, in particular the acquisition and development of vocabulary (Gathercole, 2006; Gathercole & Baddeley, 1993; Gupta, 2012). According to Baddeley and Hitch's (1974) structural view of WM, its PWM sub-component encompasses a capacity-limited phonological short-term store (limited in terms of the amount of information it actively holds and the brief duration of such holdings and an articulatory rehearsal mechanism, analogous to sub-vocal/inner speech), which prevents the actively held information from decaying (Baddeley, 2003a, 2012, 2015; Gathercole, 2007; Gathercole & Baddeley, 1993).