The Slow Rate of Visual Working Memory Consolidation Is a Structural Limit
Carlos, Brandon John
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Extensive research has focused on the limited storage capacity of working memory (WM), i.e., the maximum amount of information that can be maintained in WM. However, a relatively understudied limitation of WM involves the processing speed by which sensory information can be transformed into a WM representation that is resistant to distraction from ongoing perception and cognition. The speed of this “consolidation” process is the subject of conflicting results. Researchers have arrived at estimates of the consolidation time course using distinct paradigms ranging from 25 ms to 1 s, meaning more than an order of magnitude of variability. The extremely large variation in WM consolidation speed estimates across measurement approaches motivated the current work’s goal of determining whether consolidation speed is under strategic control or is a stable structural constraint of WM encoding. Here, the slower (1 s) measurement of WM consolidation of visually-presented verbal stimuli (i.e., letters) was replicated by using retroactive interference (RI; Nieuwenstein & Wyble, 2014)—essentially, measuring how long it takes after a WM sample array is presented for the representation in WM to no longer be vulnerable to distraction by performing a speeded second task (T2). Then, the RI results were extended to more standard visual WM stimuli (i.e., color patches). Further, slow consolidation was obtained regardless of the relative prioritization of WM encoding vs. T2, supporting the structural account. However, no RI was obtained when T2 was unspeeded. Finally, a sensorimotor decision and motor response to T2 were required to obtain RI. Given that RI was robust to varying WM probes, WM stimuli, and that slow consolidation was obtained regardless of strategic demands, the present study supports the structural account of WM consolidation.