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Conflict Adaptation in Bilinguals: The Importance of Behavioral Evidence in Cognitive Neuroscience
Oliver Sawi1,2, Hunter Johnson1, Kenneth Paap1; 1San Francisco State University, 2University of Connecticut Tables and Figures Results Introduction Does the additional session improve performance? Executive Function Executive functions (EFs) consist of a set of general-purpose control processes believed to be central to the self-regulation of thoughts and behaviors that are instrumental to accomplishing goals. EFs include components for inhibitory control, switching, monitoring, and updating. The important first question: Does the second session produce significant improvements in performance.? A factorial ANOVA (with days, blocks, and trial type as repeated measures and language group as a between-subject factor) on the mean RTs. Significant main effect of Day, F(1, 77) = 76.60, p < .001, = .499 global RT in the flanker task improved from 540 ms to 509 ms Similarly, an ANOVA on the flanker effects (mean RT incongruent – mean RT congruent) with days and blocks as repeated measures and language group as a between-subject variable was conducted Significant main effect of Day, F(1, 77) = 6.20, p = .015, = .074 overall flanker effect significantly decreased from 83 ms to 76 ms The Bilingual Advantage Hypothesis Bilinguals have two lexicons that remain active even when the context strongly supports the intention to use only one of them (e.g., Brysbaert, 1998), necessitating a mechanism for maintaining separation between languages. If this mechanism (Green 1998) involves the same executive functions used in all domains, then bilinguals accrue massive amounts of practice that should generalize across cognitive domains and make them less vulnerable to interference in nonlinguistic tasks. Figure 2 & 3: Reduction in Conflict Effect (Flanker) in Abutalebi et al. (2012). While individual t-tests are significant, direct comparisons between groups are not. The Alignment Problem, Valence Ambiguity Do Bilinguals Adapt Better to Conflict? Cortical areas shown to be involved in managing two languages overlap with inhibitory control, switching (Bialystok, Craik, & Luk, 2012). Neural processing of bilinguals, monolinguals differs during the performance of EF tasks. Reorganization does not logically need to result in more efficient performance (e.g., it could result in comparable performance) THe observed neural differences must be aligned with the behavioral differences bilingual advantages in performance can be confirmed. We propose that the existence of a behavioral phenomenon can only be adjudicated at the behavioral level similar to Hilchey and Klein (2011). Group x Day interaction in the analysis of the flanker interference (RT) scores was not significant, F(1, 77) = 2.60, p = .111, = .033. Nonsignificant trend is in the opposite direction: Monolinguals had an 11ms improvement compared to 2ms in Bilinguals Group x Day interaction on Global RT in the flanker task showed no main effect of group, F(1, 77) = 0.002, p = .967, < Group was not involved in any significant interactions. A full factorial ANOVA with days, blocks, and trial type as repeated measures factors and language group as a between-subject variable was conducted on the accuracy scores. Participants did make 3.3% more errors on the incongruent trials compared to the congruent trials, but even that main effect was not significant, F(1, 77) = 1.57, p = .214, = Overall, the ANOVA on the accuracy scores yielded no significant main effects or interactions. Previous Inconsistent Findings of Conflict Adaptation in Bilinguals Abutalebi et. al (2012) reported across blocks, bilinguals significantly reduced the conflict effect in the Flanker test (36 ms) while monolinguals did not (11 ms) There was no reported comparison of LANG X EFFECT. Given the information provided (e.g. n, we computed the independent groups t-value t(29) = 1.48, p = .15 (n.s) Abutalebi et al (2012) takes this evidence as the behavioral basis for findings in ACC in which bilinguals both have less ACC activation in the first session and have a radical decrease in activation in block 2 Two earlier reports (Costa, Hernandez, & Sebastian-Galles, 2008; and Costa, Hernandez, Costa-Faidella, & Sebastian-Galles, 2009, 75% congruent condition) show the opposite pattern, that is, bilingual advantages in the flanker effect are significant in the first block but vanish by the third block. Three other reports simply showed no language-group differences in any block (Costa et al., 2009, 50% congruent condition; Paap & Greenberg, 2013; Paap & Sawi, 2014). Discussion Can Neuroscience Results Bolster the Weak Behavioral Evidence? Might it be the case that neuroscience measures are simply more sensitive than the behavioral measure to a true bilingual advantage in adaptation to conflict? In our view there are problems with that argument. The argument assumes that the advantage is real in the population distributions, but that it is masked by variability in the RT measures. The evidence that bilinguals reduce their conflict effect more so than the monolinguals is weak - it is non-existent or contradicted in other studies. The sensitivity argument can account for the weak evidence, but cannot account for the reverse findings, especially with n’s as large as 100 participants. Figure 4. The flanker effects for bilinguals and monolinguals across blocks within a single session- The combined results of Paap and Greenberg (2013) and Paap and Sawi (2014). Scores are averaged across the two studies and are based on 108 bilinguals and 112 monolinguals Method Are Neural Differences Marked as Advantages or Disadvantages? Participants. The participants were San Francisco State University students. Language Characteristics described in Table 1. Design and Procedure. Our flanker task was identical to that used by Paap and Greenberg (2013). The sequence of events was the same as shown in Figure 1 for Abutalebi et al. Each of the three experimental blocks consisted of 32 congruent and 32 incongruent trials presented in random order. To explore possible Language Group x Practice interactions beyond just two or three blocks in a single session we tested a large group of bilinguals and monolinguals in two sessions (of 3 blocks each) separated by about one week If the ACC is responding to the amount of conflict detected (or the intensity of the specified control “commanded” by the ACC as described by Shenhav, Botvinick, and Cohen. 2013), then the Abutalebi et al. results would mean that bilinguals were registering less conflict and/or specifying less control. Differences in ACC activity between congruent and incongruent trials may be reflecting differences in the efficiency of conflict resolution, but they might also be reflecting differences in the amount of conflict detected, differences in the intensity of the specified control, the differences in the cost-benefit analysis that presumably underlies the identity and intensity of the specified control, or even differences in memory storage and retrieval. Providing consistent and compelling behavioral evidence will be an important step toward ascertaining the correct interpretations of the neuroscience data. Figure 5. The Group x Day interaction is not significant, but the nonsignificant trends are opposite the pattern reported by Abutalebi et al., that is, the monolinguals show the numerically greater reduction in the magnitude of the flanker effect.
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