Meta-Analysis Reveals a Bilingual Advantage That Is Dependent on Task and Age.

Debate continues on whether a bilingual advantage exists with respect to executive functioning. This report synthesized the results of 170 studies to test whether the bilingual advantage is dependent on the task used to assess executive functioning and the age of the participants. The results of the meta-analyses indicated that the bilingual advantage was both task- and age-specific. Bilinguals were significantly faster than monolinguals (Hedges' g values ranged from 0.23 to 0.34), and significantly more accurate than monolinguals (Hedges' g values ranged between 0.18 and 0.49) on four out of seven tasks. Also, an effect of age was found whereby the bilingual advantage was larger for studies comprising samples aged 50-years and over (Hedges' g = 0.49), compared to those undertaken with participants aged between 18 and 29 years (Hedges' g = 0.12). The extent to which the bilingual advantage might be due to publication bias was assessed using multiple methods. These were Egger's Test of Asymmetry, Duval and Tweedie's Trim and Fill, Classic Fail-Safe N, and PET-PEESE. Publication bias was only found when using Egger's Test of Asymmetry and PET-PEESE method, but not when using the other methods. This review indicates that if bilingualism does enhance executive functioning, the effects are modulated by task and age. This may arise because using multiple languages has a highly specific effect on executive functioning which is only observable in older, relative to younger, adults. The finding that publication bias was not uniformly detected across the different methods raises questions about the impact that unpublished (or undetected) studies have on meta-analyses of this literature.

The Effect of Visual Articulatory Information on the Neural Correlates of Non-native Speech Sound Discrimination.

Behavioral studies have shown that the ability to discriminate between non-native speech sounds improves after seeing how the sounds are articulated. This study examined the influence of visual articulatory information on the neural correlates of non-native speech sound discrimination. English speakers' discrimination of the Hindi dental and retroflex sounds was measured using the mismatch negativity (MMN) event-related potential, before and after they completed one of three 8-min training conditions. In an audio-visual speech training condition (n = 14), each sound was presented with its corresponding visual articulation. In one control condition (n = 14), both sounds were presented with the same visual articulation, resulting in one congruent and one incongruent audio-visual pairing. In another control condition (n = 14), both sounds were presented with the same image of a still face. The control conditions aimed to rule out the possibility that the MMN is influenced by non-specific audio-visual pairings, or by general exposure to the dental and retroflex sounds over the course of the study. The results showed that audio-visual speech training reduced the latency of the MMN but did not affect MMN amplitude. No change in MMN amplitude or latency was observed for the two control conditions. The pattern of results suggests that a relatively short audio-visual speech training session (i.e., 8 min) may increase the speed with which the brain processes non-native speech sound contrasts. The absence of a training effect on MMN amplitude suggests a single session of audio-visual speech training does not lead to the formation of more discrete memory traces for non-native speech sounds. Longer and/or multiple sessions might be needed to influence the MMN amplitude.

Dissociable implicit sequence learning mechanisms revealed by continuous theta-burst stimulation.

The primary motor area (M1) has been implicated in visuomotor sequence learning. However, it has been suggested there are multiple neural networks that undertake visuomotor sequence learning. The role of M1 in sequence learning may be specific to learning simple sequences comprising predictable associations between adjacent movements. This study aimed to investigate the role of M1 in learning simple ("first-order conditional") and more complex ("second-order conditional") sequences. It was hypothesized that continuous theta burst stimulation (cTBS) over M1 would result in poorer learning of the simple sequence only. Forty-eight healthy adults received cTBS to either M1 or the parietal lobe or received sham cTBS before immediately completing 2 visuomotor sequence learning tasks. The tasks only differed in relation to the structure (i.e., simple vs. complex) of the sequence. The group who received cTBS over M1 demonstrated significantly poorer learning of the simple sequence in comparison to the more complex sequence. The parietal lobe stimulation and sham stimulation did not affect learning of either sequence. This is the first study to show differential involvement of M1 in visuomotor sequence learning, dependent on sequence structure. The study provides new evidence that sequence learning might be supported by different networks in the brain. Specifically, M1 sequence learning appears to be important for learning simple item-to-item associations but not for more complex sequences. (PsycINFO Database Record (c) 2019 APA, all rights reserved).