Fast modulation of executive function by language context in bilinguals

Abstract

Mastering two languages has been associated with enhancement in human executive control, but previous studies of this phenomenon have exclusively relied on comparisons between bilingual and monolingual individuals. In the present study, we tested a single group of Welsh-English bilinguals engaged in a nonverbal conflict resolution task and manipulated language context by intermittently presenting words in Welsh, English, or both languages. Surprisingly, participants showed enhanced executive capacity to resolve interference when exposed to a mixed compared with a single language context, even though they ignored the irrelevant contextual words. This result was supported by greater response accuracy and reduced amplitude of the P300, an electrophysiological correlate of cognitive interference. Our findings introduce a new level of plasticity in bilingual executive control dependent on fast changing language context rather than long-term language experience.

Figure 1.

Experimental design and stimulus examples. Each trial began with a fixation cross that lasted for 500 ms and was followed by a blank screen of 200 ms. The stimulus was then presented at the same location as the fixation cross for 1500 ms or as soon as the participant responded to it. The intertrial interval was 2000 ms.

Figure 2.

Reaction times (bars; left axis) and error rates (bullets; right axis) in the flanker task for the English, Welsh, and mixed contexts. For reaction time data, the congruent condition (C) is presented in white and the incongruent condition (I) in gray. For error data, the congruent condition is presented in white and the incongruent condition is in black. The asterisks indicate significant differences (p < 0.05). Error bars depict SEM in all cases.

Figure 3.

A–C, Event-related brain potentials and topographies elicited in the flanker task in the English (A), Welsh (B), and mixed (C) contexts. The waveforms depict linear derivations of brain potentials from nine electrodes (C1, C2, Cz, P1, P2, Pz, CP1, CP2, and CPz). The shaded areas represent significant differences between conditions (e.g., p < 0.05) over a minimal period of 30 ms. The scaled topographies show the ERP differences elicited by the flanker effect. D, Millisecond-by-millisecond t test comparisons between congruent and incongruent conditions (purple, English; green, Welsh; red, Mixed). The dotted line represents the threshold of significant differences.

Figure 4.

ERPs of between-block comparisons: English–Welsh (top), Welsh–mixed (middle), and English–mixed (bottom) for the congruent (left) and incongruent (right) conditions. ERPs are a linear derivation of the electrodes shown on the schematic head.