Phonological Loop and Central Executive Processes in Mental Addition and Multiplication

Summary Our investigations address the role of subsystem-specific working memory resources in mental arithmetic. The dual-task paradigm was used to present addition and multiplication sums with subsystem-specific concurrent tasks. In the first experiment neutral tapping (NT) was contrasted to articulatory suppression (AS), canonical number articulation (CN) and random number generation (RN) as secondary tasks. As primary task sums (two levels of difficulty) had to be solved mentally, and results had to be spoken out loud. AS mainly affected difficult addition sums, CN decreased performance on easy and difficult addition sums and difficult multiplication sums and RN produced interference on all sums. In a second experiment we used random letter generation (RL) and canonical letter articulation (CL) in addition to NT and AS in order to rule out effects of semantic interference. A result-pattern comparable to the first experiment was observed. Our conclusion is that the elementary process of fact retrieval requires central executive resources, that temporarily storing partial results relies on phonological loop resources, and that keeping track of a carry operation is monitored by the central executive. Further reliance of calculation processes on subsystem-- specific working memory resources is discussed within the working memory framework. Key words: working memory, central executive, dual-task paradigm, mental arithmetic Mental calculations are an everyday activity for adults and important for educational settings from (pre-) school on. The general interest has grown with the increasing debate on dyscalculic and acalculic persons. That is why for the last two decades cognitive processes in mental arithmetic have more and more been investigated (for an overview see Dehaene, 1992, Donlan, 1998). Working memory models, such as Baddeley and Hitch's (1974, Baddeley, 1986), serve as theoretical frameworks for recent research in the field of short-term arithmetical information processing (Logie, Gilhooly & Wynn, 1994; Lemaire, Barrett, Fayol & Abdi, 1994; Lemaire, Abdi & Fayol, 1996; De Rammelaere, Stuyven & Vandierendonck, 1999; Adams & Hitch, 1998; Seitz & Schumann-Hengsteler, 2000), particularly, when results focus on basic processing resources and central processes that might be involved in mental arithmetic. Within this theoretical context subsystem specific resources, for example phonological processes, were found to be used in mental addition (Logie, Gilhooly & Wynn, 1994; Lemaire, Abdi & Fayol, 1996; De Rammelaere, Stuyven & Vandierendonck, 1999) and in mental multiplication of difficult sums (e.g. 9 x 16 =) as well (Seitz & Schumann-- Hengsteler, 1997, 2000). Working memory processes of a more general nature, like central executive resources, are involved in mental addition and mental multiplication (Lemaire, Abdi & Fayol, 1996; Seitz & Schumann-Hengsteler, 2000). Access to long-term stored arithmetical knowledge, in this case pure fact retrieval, is supported by central executive resources only (Lemaire, Abdi & Fayol, 1996; Seitz & Schumann-Hengsteler, 2000). Processes of short-term arithmetical information storage, for example storage of partial results, depend on the functioning of the phonological loop (Logie, Gilhooly & Wynn, 1994; Hitch, 1978). The dual-task-paradigm is the methodological approach most frequently chosen for this kind of research (Logie, Gilhooly & Wynn, 1994; Lemaire, Barrett, Fayol & Abdi, 1994; Lemaire, Abdi & Fayol, 1996; De Rammelaere, Stuyven & Vandierendonck, 1999; Adams & Hitch, 1998; Seitz & Schumann-Hengsteler, 2000). The assumption is that pre-loading a specific working memory subsystem with a secondary task while a goal task, in this case mental arithmetic, is performed, causes a decrease of performance in mental arithmetic, if both tasks demand the same subsystem-specific resources of the system's limited capacity. …