Testing the limits of intentional linguistic control in bilinguals

研究人员研究了使双语者在几乎不受其他语言干扰的情况下说所需语言的心理过程(及其神经基础)(S)。一种流行的实验室范式要求双语者按需转换语言，结果表明，转换会导致延迟和不准确的口语反应--“转换成本”。“转换成本”的一个可能来源是，用所需语言进行交流可能会受到另一种语言的干扰(S)。双语者如何解决这种干扰以选择预期的语言，是一个尚未得到满意答案的根本问题。该项目建议测试和评估最近提出的两个有趣而又有争议的假说。双语者能“关掉”不想要的语言吗？一个公认的理论认为，当在想要的语言中寻找一个词条(词)时，双语者会抑制在另一种语言(S)中具有相同意思的词(S)。最近，这一“抑制控制”框架被扩展，提出双语者可能不仅能够有意抑制特定的单词，而且能够有意抑制一种不想要的语言--被称为“全局抑制”。这一假说的证据来自“反向语言支配”效应：当双语者断断续续地使用两种语言时，他们的优势/强势语言(下称L1)的表现比非优势/弱语言(下称L2)差，这可能是因为在用L2交流时不得不更强地抑制L1，随后不得不克服这种抑制才能再次使用L1。然而，最近的一项荟萃分析得出结论，现有数据并不能明确表明反向优势的存在。因此，全局抑制的证据是有限的和间接的。为了解决这种情况，该项目将：-采用参与者内部的设计(以最大化权力)，并开发将鼓励全局抑制(如果存在)的条件，以与其他需要很少/不需要全局抑制的条件形成对比。例如，参与者将首先被要求生成他们在第一语言中更常用的二语单词。大概，相对于初始L2块包含容易在L2中产生的项的控制条件，这应该涉及L1的全局抑制，以防止来自L1的干扰，从而损害L1中的性能(因此，较少需要抑制较少干扰的L1)。-使用新的多变量脑电位解码(EEG)来得出并在时间上跟踪L1和L2激活的潜在EEG“信号”，以寻找任何全局抑制的迹象。语言转换可以“免费”吗？如前所述，有充分的证据表明，当双语者被要求转换语言时(例如，通过呈现视觉提示，指定要用于下一刺激的语言)，总是会有表现上的“转换成本”。然而，最近有人提出，当双语者有机会自由转换时，他们可以采用“混合语言处理模式”，在这种模式下，无论来自哪种语言，都会说出最适合检索的单词，这应该会消除转换成本。事实上，最近的两项研究声称提供了这种免费自愿转换的证据。然而，这些研究的功率相对较低，依赖于非常有限的刺激集，并指示参与者在整个实验过程中记住对任何给定的刺激使用相同的语言。后者鼓励参与者将此作为一项记忆(联想提取)任务。为了解决上述关切，该项目将研究使用大量刺激进行免费语言转换的可能性，避免刺激重复，并取消对特定刺激的任何语言要求，以排除线索联想检索方面的解释，并确保自由选择语言。

Researchers have investigated the psychological processes (and their neural underpinnings) that enable bilinguals to speak the desired language with little/no intrusion from the other language(s). One popular laboratory paradigm that asks bilinguals to switch languages on demand, has shown switches to result in delayed and less accurate spoken responses - the "switch cost". A likely source of the "switch cost" is that communication in the required language can be subject to interference from the other language(s). How bilinguals resolve such interference to select the intended language is a fundamental question still awaiting a satisfactory answer. The project proposes to test and evaluate two intriguing, yet contentious, hypotheses put forward recently.Can bilinguals "switch off" the unwanted language?One established theory argues that when looking for a lexical item (word) in the desired language, bilinguals inhibit the word(s) with the same meaning in the other language(s). More recently, this "inhibitory control" framework has been extended by the suggestion that bilinguals may be able to intentionally suppress not only specific words, but an unwanted language - referred to as "global inhibition". Evidence for this hypothesis comes from the "reverse language dominance" effect: when bilinguals use two languages intermittently, performance in their dominant/strong language (henceforth L1) is worse than in the non-dominant/weak language (henceforth L2), presumably as a result of having to inhibit L1 more strongly while communicating in L2, and subsequently having to overcome that inhibition to use L1 again. However, a recent meta-analysis concluded that the available data do not unequivocally indicate the existence of reverse dominance. Thus the evidence for global inhibition is limited and indirect.To address this state of affairs, the project will:- employ a within-participants design (to maximise power) and develop conditions which will encourage global inhibition (should it exist) to contrast with other conditions requiring little/no global inhibition. For instance, participants would first be asked to generate words in L2 which they more commonly use in L1. Presumably, this should engage global inhibition of L1 to prevent interference from it, subsequently impairing performance in L1, relative to a control condition where the initial L2 block contains items that are easy to generate in L2 (hence less need to inhibit a less interfering L1). - employ novel multivariate decoding of brain potentials (EEG) to derive and temporally track latent EEG "signatures" of the activation of L1 and L2 to look for any signs of global inhibition.Can language switches be "cost-free"? As mentioned previously, there is ample evidence that when bilinguals are required to switch languages (e.g. by presenting a visual cue specifying the language to use for the following stimulus), there is invariably a performance "switch cost". However, recently it has been proposed that when bilinguals have the opportunity to switch freely they can adopt a "mixed-language processing mode" wherein the word most available for retrieval is spoken irrespective of the language it comes from, which should eliminate the switch cost. Indeed, two recent studies claimed to provide evidence of such cost-free voluntary switching. However, these studies had relatively low power, relied on very limited stimulus sets and instructed participants to remember to use the same language for any given stimulus throughout the experiment. The latter encourages participants to approach this as a memory (associative retrieval) task. To address the aforementioned concerns, the project will examine the possibility of cost-free language switching using large sets of stimuli, avoiding stimulus repetitions, and removing any language requirement for specific stimuli, to rule out the interpretation in terms of cued associative retrieval and ensure free choice of language.