Testing the Predictions of the Central Capacity Sharing Model.

Abstract

The divergent predictions of 2 models of dual-task performance are investigated. The central bottleneck and central capacity sharing models argue that a central stage of information processing is capacity limited, whereas stages before and after are capacity free. The models disagree about the nature of this central capacity limitation. The central bottleneck model claims that central processing acts on only 1 task at a time and, therefore, constitutes a bottleneck that processes tasks serially. The central capacity sharing model postulates that the central stage is a limited-capacity parallel processor that divides resources among to-be-performed tasks. As a result of this difference, in the psychological refractory period paradigm, the central capacity sharing model predicts that lengthening Task 2 precentral processing will improve Task 1 performance at short stimulus onset asynchronies, whereas the central bottleneck model does not. Results of 2 experiments confirm the prediction of the central capacity sharing model.Keywords: capacity sharing, information processing, dual-task, psychological refractory period (PRP), attention Researchers have known for over 70 years that when people are required to perform two tasks in rapid succession, performance on one or both of these tasks suffers. This phenomenon is known as dual-task interference, and it can be striking and severe. Although the human brain is a powerful information processing device, the observation of dual-task interference indicates a performance limit on what the brain can do. Much research has been conducted exploring dual-task interference, but the source of this limitation continues to be debated. The Psychological Refractory Period ParadigmIn 1931, Telford developed the psychological refractory period (PRP) paradigm to explore dual-task performance. The paradigm has since been used extensively (DeJong, 1993(DeJong, , 1995McCann & Johnston, 1992;Pashler, 1991Pashler, , 1994Pashler & Johnston, 1989;Smith, 1967;Welford, 1952). In the PRP paradigm, subjects perform two tasks in rapid succession. On each trial, two stimuli are presented, each of which requires its own speeded response. The tasks that are used generally do not take long to perform (typically less than 1 s when performed alone) and can seem trivial when performed in isolation. The temporal gap between the onsets of the two stimuli-the stimulus onset asynchrony (SOA)-is varied, and reaction time (RT) and accuracy are measured. As the SOA is shortened, a dramatic limitation in information processing is revealed. At long SOAs, performance on both tasks approaches single-task performance. However, as the SOA is decreased, performance on the second task becomes increasingly worse. At the shortest SOAs, RTs to the second task (RT2s) are often several hundred milliseconds longer than they are at long SOAs. At sufficiently short SOAs, the slope of the RT2 curve (as a function of SOA) approaches Ϫ1, indicating that decreases in the SOA are fully transferred to RT2. This increase in RT2 with d...

Are processing limitations of visual attention and response selection subject to the same bottleneck in dual-tasks?

“…An overview can be found here. 5 The collected RT graphs show full absorption at short SOA for various studies (i.e., Pashler & Johnston, 1989;Maquestiaux, Hartley, & Bertsch, 2004;Tombu & Jolicoeur, 2005;Jentzsch, Leuthold, and Ulrich, 2007. Our RT2 graphs of set sizes 6 and 12 for both target present and target absent coincide with these examples.…”

“…As discussed above, the attentional demands in target absent set size 18 exclusively exceeded the slack time leading to partial absorption. To further explain this discrepancy, it has to be noted that we tested the hypothesis of concurrent processing of visual attention and response selection by increasing the set size for the relevant process in Task 2 without changing the physical appearance of the stimuli, whereas other research groups mostly changed the physical appearance of the to be processed stimuli in Task 2 without changing the number of the stimuli (i.e., Jentzsch et al, 2007;Maquestiaux, Hartley, & Bertsch, 2004;Pashler & Johnston, 1989;Tombu & Jolicoeur, 2005). It should be considered that changing the number of the to be processed stimuli could be more demanding than changing their physical appearance, which, in turn prevents full absorption in extreme conditions.…”

A cognitive framework for explaining serial processing and sequence execution strategies

“…Separate processors at three processing levels is, by and large, consistent with the different types of processing resources that account for the patterns of interference between two simultaneously executed tasks (Wickens, 1984(Wickens, , 2008, and also with the assumption of the Theory of Event Coding that "early perceptual" and "late motor" processes are carried out independently from central processes . The notion of a limited set of processors has been further used to explain the central bottleneck that is responsible for slowing the second of two successive choice reaction time tasks in the Psychological Refractory Period task (Meyer & Kieras, 1997;Tombu & Jolicoeur, 2005).…”

“…The cognitive loop and motor loop arrows correspond with the plan-based and chunking execution modes, respectively Importantly, studies with the Psychological Refractory Period paradigm and the Discrete Sequence Production task allow allocating the processing stages of the Additive Factors Model and Subprogram-Retrieval Model to the above proposed processors. The observation that the second of two successive choice RT tasks in the Psychological Refractory Period paradigm is slowed by the first choice RT task is generally explained by a central processor being allocated to the second task only after it has completed the processing stages of the first task (Byrne & Anderson, 2001;Meyer & Kieras, 1997;Pashler, 1984;Pashler & Christian, 1994;Ruthruff, Pashler, & Klaassen, 2001;Tombu & Jolicoeur, 2005). Response selection is the prototypical processing stage that would be responsible for the central processing bottleneck (Pashler, 1994), but the central bottleneck was later found to also affect stimulus identification, mental rotation, and other processing stages involving the retrieval of knowledge from memory (Johnston & McCann, 2006;Meyer & Kieras, 1997;Pashler, 1994;Pashler & Christian, 1994;.…”

Beyond a mask and against the bottleneck: Retroactive dual-task interference during working memory consolidation of a masked visual target.

“…In considering how such interference might arise, we can nevertheless conceive of two possibilities (cf. Tombu & Jolicoeur, 2005). The first adheres to the notion of a central bottleneck and proposes that since WMC and response selection cannot be performed in parallel, it must be the case that the response selection task interrupted the ongoing consolidation of the earlier stimuli.…”