Topics in psycholinguistics and the neurocognition of language rarely attract the attention of journalists or the general public. One topic that has done so, however, is the potential benefits of bilingualism for general cognitive functioning and development, and as a precaution against cognitive decline in old age. Sensational claims have been made in the public domain, mostly by journalists and politicians. Recently (September 4, 2014) The Guardian reported that “learning a foreign language can increase the size of your brain”, and Michael Gove, the UK's previous Education Secretary, noted in an interview with The Guardian (September 30, 2011) that “learning languages makes you smarter”. The present issue of BLC addresses these topics by providing a state-of-the-art overview of theoretical and experimental research on the role of bilingualism for cognition in children and adults.

The relation between bilingualism and cognition is informative about the connection between language and mind. From the perspective of language, the question is how bilingualism might help or hinder cognition – narrowly interpreted here as executive function. From the perspective of higher cognition, the question is what kinds of experiences improve executive function. Reported cognitive benefits from bilingualism range from none to substantial as a function of age, type of bilingualism (e.g., life-long balanced vs later-onset or infrequent use of the other language), syntactic relation between the two languages, socio-economic and immigrant status, task, and laboratory. To understand the variability and inconsistencies in results with bilingualism, I analyze concepts of executive function and cognitive reserve and examine the range of factors (such as active video game playing, education, musical training, and aerobic exercise) that are known to correlate with or to improve executive function. I suggest that a) “executive function” is a complex set of cognitive processes, the components of which are sometimes minimally correlated with each other, depending on the task; b) bilingualism is inconsistently correlated with superior executive function and delayed onset of dementia; c) all speakers (mono- or bilingual) have non-linguistic ways of improving executive function; and d) benefits from bilingualism – and all cognitively challenging activities – are inconsistent because individuals vary in the number and kinds of experiences they have that promote superior executive function.

At the outset of her article Valian (2014) advocates for the existence of an effect of bilingualism on executive control (EC). She is commended for being very clear about her position. She argues that: “There is a benefit of bilingualism for executive function, but that benefit competes with other benefits that both mono- and bilinguals have to varying degrees. Depending on the composition of each group in any given experiment, the other benefits may be more plentiful in the monolingual than bilingual group (or sufficiently plentiful in both groups), so that the benefits of bilingualism are invisible. This is the possibility that I favor.”

Valian (2014) suggests that the messy state of the literature examining the effects of bilingualism on executive functioning (EF) stems from lack of clarity in how EFs are defined and measured, and from lack of control over other factors that can modulate EF. We argue that the lack of clarity in how bilingualism is defined and measured is no less problematic. We focus our commentary on two related issues.

Scholars and educators were once concerned that encouraging children to learn more than one language might have adverse cognitive consequences (Darcy, 1953). And for some linguistic capacities (e.g., fluency, vocabulary) this is often true (Bialystok, Craik & Luk, 2012). Unfortunately, such individual costs might discourage governmental policies that are aimed at fostering multi-lingualism, despite its widely acknowledged societal benefits. Peal & Lambert (1962) helped overcome this concern and through her “myth-dispelling” efforts and prodigious empirical output, Bialystok has pushed the pendulum of opinion in the opposite direction.

In the last two decades there has been an explosion of research on bilingualism and its consequences for the mind and the brain (e.g., Kroll & Bialystok, 2013). One reason is that the use of two or more languages reveals interactions across cognitive and neural systems that are often obscured in monolingual speakers of a single language (e.g., Kroll, Dussias, Bogulski & Valdes Kroff, 2012). From this perspective, the interest in bilingualism is about developing a platform to ask questions about the ways that cognitive and neural networks are engaged during language use, in different learning environments, and across the lifespan. Another reason is that an emerging body of research on the consequences of bilingualism suggests that language experience changes cognition and the brain (e.g., Abutalebi, Della Rosa, Green, Hernandez, Scifo, Keim, Cappa & Costa, 2012; Bialystok, Craik, Green, & Gollan, 2009). Some of these changes have been claimed to produce cognitive advantages (see Bialystok et al., for a review of bilingual advantages and disadvantages).

In the keynote article, “Bilingualism and Cognition”, Valian (2014) has reviewed current research on comparing executive function (EF) in monolingual and bilingual individuals across the lifespan. The conclusion is that there are inconsistent EF advantages from bilingualism and all other cognitive challenging activities primarily because individual differences in these cognitive challenging experiences may collectively attribute to superior EF resulting in inconsistent EF benefit attributable to a single experience. In essence, variability in study participants’ experience and tasks contributes to the inconsistency in the behavioral outcomes observed in monolinguals and bilinguals. Notably, Valian suggests that monolinguals may also engage in other cognitively challenging activities, which have not been accounted for in individual studies, thereby resulting in improved EF similar in magnitude to that related to bilingual experience. Although it was not specified which cognitively challenging activity is more likely to be engaged by monolinguals more than by bilinguals, the question at heart is: is there an EF advantage that can be specifically attributed to bilingual experience? The review addressed in the keynote demonstrates seemingly inconsistent patterns of results. In this commentary, I would like to suggest that, in addition to task measurements, individual bilingual experience is dynamic and multifaceted. Moreover, bilingual experience varies in different communities. Consequently, one potential source of explanation for the inconsistent results in between-group EF performances is the characteristics of the bilinguals (and monolinguals) and their social environments included in these studies.

In her keynote paper, Valian (2014) provides a comprehensive review of the literature that examines whether bilingual individuals outperform monolingual participants on various executive processing tasks. The author acknowledges that numerous factors contribute to the outcomes, such as variations in participants’ profile, differences in target functions, as well as variants of tasks and procedures. She also says in her review that, on the one hand, researchers use different tasks to measure similar functions; while, on the other hand, each of these tasks target somewhat different aspects of executive processing. The most widely used tasks, such as the Stroop or flanker tasks, measure several components of executive functions simultaneously.

Valian (2014) argues that current approaches in the study of bilingualism's beneficial effects on executive functions and cognition are at best methodologically weak. There is no unanimity on what constitutes executive function and which tasks measure it. I agree with her view that executive function is not a single phenomenon but a collection of processes. Different tasks measure different aspects of them. Performance on different executive function tasks is related to the particular cognitive demands of the tasks as well as the participants’ profile. It does not follow necessarily that negotiating two languages should lead to an enhancement of ability on that task. Therefore, no single task can capture the cognitive benefits of bilingualism. Valian proposes that factors such as education, socio-economic status, and even extracurricular skills involving sports and exercise could boost executive functioning independent of bilingualism.

In her acknowledgments Valian (2014) speculates that some of her colleagues may agree with at least some of her conclusions. I agree with most. These include that bilingualism is inconsistently correlated with superior executive function, that the overall benefits of bilingualism reported in some experiments may signify benefits unrelated to executive function (EF), that all speakers have non-linguistic ways of improving EF, and that tests for bilingual advantages should be aimed at specific mechanisms of bilingual experience and their corresponding components of EF. The remainder of my 1,000 words will be devoted to rather subtle points of disagreement.

The study of bilingualism has generated great interest about a core issue: does the experience of using two or more languages lead to enduring changes in the bilingual brain. This issue is often framed as a search for bilingual advantages in cognition, most notably behavioral performance on executive control tasks. Valian's timely keynote (2014) adopts this framing.

We applaud Valian's (2014) thoughtful analysis of the cross-sectional and longitudinal studies that have thus far contributed to our knowledge about the role of bilingualism in cognitive aging. In evaluating the literature as summarized by Valian, we think it is useful to distinguish between the following four research questions and representative analytic approaches: (1) cross-sectional associations between bilingualism and executive function (e.g., regression), (2) longitudinal associations between bilingualism and change in executive function (e.g., growth curve modeling), (3) bilingualism as a predictor of dementia incidence (e.g., time-to-event analysis), and (4) bilingualism as a source of cognitive reserve (e.g., comparisons of brain pathology between bilinguals and monolinguals matched on cognitive performance).

The goal of my keynote article, “Bilingualism and Cognition” (Valian, 2014), was to resolve the inconsistencies in effects of bilingualism on executive functions, whether the individuals were children, young adults, or old people. To summarize (and sharpen) my argument:

1. 1. Especially in children and young adults, benefits of bilingualism for executive functions are not reliable. In old people, there are benefits for executive functions but contradictory results on delay of cognitive impairment, depending on whether studies are retrospective or prospective.

2. 2. All experiences that have benefits for executive functions and aging – and there are many – yield inconsistent effects. Bilingualism is not alone.

3. 3. Three reasons for inconsistencies in bilingualism and other experiences are:

   1. a. Executive function and cognitive reserve are broad cover terms for a variety of mechanisms, most of which are ill-understood. Because we mean different things by ‘executive function’ from one experiment to the next, we can both think we don't have an effect when we do and think we have an effect when we don’t.

   2. b. Tasks are impure: apparently similar tasks measure different aspects of executive function and measure other aspects of cognition as well. Because we lack a good analysis of tasks, we too often do not know what we are measuring. I encourage readers to examine the demos in the supplementary materials of the keynote article to see for themselves what the tasks are like.

   3. c. Individuals engage in many different activities that may be on a par with bilingualism in their benefits.

4. 4. Different types of bilingual experience are unlikely to explain the variability of findings, given the inconsistencies in extant data on varieties of bilingualism.

5. 5. There is a benefit of bilingualism, but bilingualism competes with other sources of benefits. Especially for children and young adults, whose daily lives are full of cognitively enriching and challenging experiences, we should expect variability in effects of being bilingual.

6. 6. The way forward is to focus on underlying mechanisms.

Language switching was studied with older adult (age 65 years and older) and young adult (18–24 years) bilinguals in a blocked-language or mixed-language condition. Results revealed small differences in reaction time (RT) between older adults and college-age participants in the blocked condition. However, older adults showed much slower RTs in the mixed condition which involves sustained switching relative to young adults. In Experiment 2, the same design was used except that participants were asked to translate an auditory word. In this condition, older adults showed a slowing effect but to a much lesser degree. Furthermore, comparisons within the mixed condition (transient switching) revealed that switching costs varied across languages and age groups. The results from the picture-naming task are consistent with models that predict deficiencies in task-set shifting in older adults especially when a stimulus activates multiple responses. Furthermore, the results indicate interesting differences in sustained and transient switching depending on the task.

The aim of the present study is two-fold. First, we investigate age-related changes to bilingual language control (bLC) mechanisms across lifespan. Second, we explore the relation between bLC mechanisms and those of the domain-general executive (EC) system by looking at age effects on these two systems. To do so, we compare the performances of the three age groups of bilinguals (young, middle-aged and elderly) in a language switching task to those of non-linguistic switching task. We found an age-related change in the non-linguistic switch cost but not in the language switch cost. Moreover, we did not find any correlation between the magnitudes of the switch costs. Taken together these results indicate that bLC is not affected by age as the EC system is, and interestingly, we add new evidence that the bLC mechanisms are not fully subsidiary to those of the domain-general EC system.

This study aimed to examine the so-called bilingual advantage in older adults’ performance in three cognitive domains and to identify whether language use and bilingual type (dominant vs. balanced) predicted performance. The participants were 106 Spanish–English bilinguals ranging in age from 50 years to 84 years. Three cognitive domains were examined (each by a single test): inhibition (the Simon task), alternating attention (the Trail Making test), and working memory (Month Ordering). The data revealed that age was negatively correlated to performance in each domain. Bilingual type – balanced vs. dominant – predicted performance and interacted with age only on the inhibition measure (the Simon task). Balanced bilinguals showed age-related inhibition decline (i.e., greater Simon effect with increasing age); in contrast, dominant bilinguals showed little or no age-related change. The findings suggest that bilingualism may offer cognitive advantage in older age only for a subset of bilinguals.

Neuropsychological theories raise the question if in late bilinguals with dementia of the Alzheimer type (DAT), the second language (L2) may be more impaired than the first (L1). We compared language performance in different tasks of oral comprehension (semantic and syntactic) and production (naming, repetition and fluency) in L1 and L2 in a group of 13 late proficient bilinguals wit DAT immersion, and a matched control group of 12 healthy late bilinguals. Two-way mixed repeated-measure ANOVAs with factors Language and Group revealed main effects of Group (p < .05) indicating that DAT affects all aspects of language. There was no Group × Language interaction, suggesting that DAT affects both languages similarly. Our study thus shows that neurodegenerative diseases affect L1 and L2 in a parallel manner, particularly at the levels of semantic, lexical and syntactic processing. These results speak in favour of a shared L1 and L2 network in late bilinguals.

Japanese–English bilinguals completed a masked phonological priming study with Japanese Katakana primes and English targets. Event related potential (ERP) data were collected in addition to lexical decision responses. A cross-script phonological priming effect was observed in both measures, and the effect did not interact with frequency. In the ERP data, the phonological priming effect was evident before the frequency effect. These data, along with analyses of response latency distributions, provide evidence that the cross-script phonological priming effects were the consequence of the activation of sublexical phonological representations in a store shared by both Japanese and English. This activation fed back to sublexical and lexical orthographic representations, influencing lexical decision latencies. The implications for the Bilingual Interactive Activation (BIA+) model of word recognition are discussed.

The main purpose of the work described in this paper is to examine the extent to which the L2 developmental changes predicted by Kroll and Stewart's (1994) Revised Hierarchical Model (RHM) can be understood by word association response behaviour. The RHM attempts to account for the relative “strength of the links between words and concepts in each of the bilingual's languages” (Kroll, Van Hell, Tokowicz & Green, 2010, p. 373). It proposes that bilinguals with higher L2 proficiency tend to rely less on mediation, while less proficient L2 learners tend to rely on mediation and access L2 words by translating from L1 equivalents. In this paper, I present findings from a simple word association task. More proficient learners provided a greater proportion of collocational links, suggesting that they mediate less when compared to less proficient learners. The results provide tentative support for Kroll and Stewart's model.