Because of enduring experience of managing two languages, bilinguals have been argued to develop superior executive functioning compared with monolinguals. Despite extensive investigation, there is, however, no consensus regarding the existence of such a bilingual advantage. Here we synthesized comparisons of bilinguals' and monolinguals' performance in six executive domains using 891 effect sizes from 152 studies on adults. We also included unpublished data, and considered the potential influence of a number of study-, task-, and participant-related variables. Before correcting estimates for observed publication bias, our analyses revealed a very small bilingual advantage for inhibition, shifting, and working memory, but not for monitoring or attention. No evidence for a bilingual advantage remained after correcting for bias. For verbal fluency, our analyses indicated a small bilingual disadvantage, possibly reflecting less exposure for each individual language when using two languages in a balanced manner. Moreover, moderator analyses did not support theoretical presuppositions concerning the bilingual advantage. We conclude that the available evidence does not provide systematic support for the widely held notion that bilingualism is associated with benefits in cognitive control functions in adults. (PsycINFO Database Record

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The efficacy of working memory (WM) training has been a controversial and hotly debated issue during the past years. Despite a large number of training studies and several meta-analyses, the matter has not yet been solved. We conducted a multi-level meta-analysis on the cognitive transfer effects in healthy adults who have been administered WM updating training with n-back tasks, the most common experimental WM training paradigm. Thanks to this methodological approach that has not been employed in previous meta-analyses in this field, we were able to include effect sizes from all relevant tasks used in the original studies. Altogether 203 effect sizes were derived from 33 published, randomized, controlled trials. In contrast to earlier meta-analyses, we separated task-specific transfer (here untrained n-back tasks) from other WM transfer tasks. Two additional cognitive domains of transfer that we analyzed consisted of fluid intelligence (Gf) and cognitive control tasks. A medium-sized transfer effect was observed to untrained n-back tasks. For other WM tasks, Gf, and cognitive control, the effect sizes were of similar size and very small. Moderator analyses showed no effects of age, training dose, training type (single vs. dual), or WM and Gf transfer task contents (verbal vs. visuospatial). We conclude that a substantial part of transfer following WM training with the n-back task is task-specific and discuss the implications of the results to WM training research.Keywords Cognitive training . Working memory . Executive functions . N-back . Meta-analysis Working memory (WM) training has stirred considerable interest amongst researchers and public at large during the past decade (von Bastian & Oberauer, 2014;Green & Bavelier, 2008;Klingberg, 2010;Lövdén, Bäckman, Lindenberger, Schaefer, & Schmiedek, 2010;Morrison & Chein, 2011). The main reason for this widespread interest is that WM has been linked to a number of important skills, such as academic achievement and general intellectual capacity (Engle, 2002;Shipstead, Redick, & Engle, 2010). Moreover, WM deficits often occur in common clinical conditions, such as dyslexia, ADHD, and major depression, as well as in normal aging (Lezak, Howieson, & Loring, 2004). As a system for shortterm maintenance and manipulation of task-relevant information (Baddeley, 2000), WM is inherently involved in all higher-level cognitive activities. Accordingly, WM training, if successful, might have wide-reaching consequences for an individual.The results from the initial WM training studies were very promising, because they suggested that it is possible to improve performance not only on the trained task but also on untrained tasks measuring other cognitive functions (Jaeggi, Buschkuehl, Jonides, & Perrig, 2008;Klingberg, Forssberg, & Westerberg, 2002). The initial enthusiasm, however, turned into a controversy as subsequent training studies reported mixed results (Brehmer, Westerberg, Bäckman, 2012;Bürki, Ludwig, Chicherio, & De Ribaupierre, 2014;Bäckman et al., 2011;Chooi ...

Several studies have suggested a bilingual advantage in executive functions, presumably due to bilinguals’ massive practice with language switching that requires executive resources, but the results are still somewhat controversial. Previous studies are also plagued by the inherent limitations of a natural groups design where the participant groups are bound to differ in many ways in addition to the variable used to classify them. In an attempt to introduce a complementary analysis approach, we employed multiple regression to study whether the performance of 30- to 75-year-old Finnish–Swedish bilinguals (N = 38) on tasks measuring different executive functions (inhibition, updating, and set shifting) could be predicted by the frequency of language switches in everyday life (as measured by a language switching questionnaire), L2 age of acquisition, or by the self-estimated degree of use of both languages in everyday life. Most consistent effects were found for the set shifting task where a higher rate of everyday language switches was related to a smaller mixing cost in errors. Mixing cost is thought to reflect top-down management of competing task sets, thus resembling the bilingual situation where decisions of which language to use has to be made in each conversation. These findings provide additional support to the idea that some executive functions in bilinguals are affected by a lifelong experience in language switching and, perhaps even more importantly, suggest a complementary approach to the study of this issue.

Updating of working memory has been associated with striato-frontal brain regions and phasic dopaminergic neurotransmission. We assessed raclopride binding to striatal dopamine (DA) D2 receptors during a letter-updating task and a control condition before and after 5 weeks of updating training. Results showed that updating affected DA activity before training and that training further increased striatal DA release during updating. These findings highlight the pivotal role of transient neural processes associated with D2 receptor activity in working memory.