We investigated how operationalizing bilingualism affects the results on a Simon task in a population of monolingual and bilingual native English speakers (N = 166). Bilingualism was measured in different ways within participants, and the measurements were used both as dichotomous and continuous variables. Our results show that the statistical significance and effect size varied across operationalizations. Specifically, the Composite Factor Score (the Language and Social Background Questionnaire’s general score), showed a bilingual disadvantage on reaction times regardless of how it was used (dichotomously or continuously). When dividing participants into monolinguals and bilinguals based on the Nonnative Language Social Use score (a Language and Social Background Questionnaire subscore), differences in accuracy and reaction times were found between the groups, but the Nonnative Language Social Use score did not predict accuracy when used as a continuous variable (only reaction times). Finally, earlier age of acquisition predicted faster reaction times, but only when used on a continuum. Effect sizes were between the small and medium range. No differences on the Simon effect were found. Our results call for cautiousness when comparing studies using different types of measurements, highlight the need for clarity and transparency when describing samples, and stresses the need for more research on the operationalization of bilingualism.

An accumulating body of evidence highlights the contribution of general cognitive processes, such as attention, to language-related skills.

The question of whether bilingualism conveys a broader advantage in executive functions has recently been controversially discussed, with the empirical findings presenting a complex pattern of positive and null results. Here we present results from three standard tasks measuring executive functions (Flanker; Simon; Spatial Stroop) in which we compared performance of English monolingual to Chinese–English bilingual young adults. Participants provided responses via movement of a computer mouse rather than the conventional key presses, which provides a rich signal of the unfolding response dynamics. Clear differences between bi- and monolinguals emerged, with the former providing more ‘efficient’ responses than the latter. Results are discussed regarding the extent to which these results can be characterised as a genuine “bilingual advantage”.

Language switching experience is assumed to have an effect on domain-general control abilities in bilinguals, but previous studies on the relationship between these two variables have generated mixed results. The present study investigated the effects of bilingual experiences on the interaction between language switching and domain-general control. Thirty-two Dutch–French bilingual young adults executed a bilingual categorisation task to assess their language switching abilities and a Simon task to assess domain-general control. The results show that global response times on the Simon task were correlated to the forward switch cost (from L1 to L2); moreover, interestingly, the forward switch cost was found to be related to recent language exposure but not to the age of second language acquisition. We suggest a monitoring account of language switching to integrate the first finding with previous studies and we interpret the second finding as support for the adaptive control hypothesis.

A question central to bilingualism research is whether representations from the contextually inappropriate language compete for lexical selection during language production. It has been argued recently that the extent of interference from the non-target language may be contingent on a host of factors. In two studies, we investigated whether factors such as word-type and individual differences in inhibitory control capacities influence lexical selection via a cross-modal picture-word interference task and a non-linguistic Simon task. Highly proficient French–English bilinguals named non-cognate and cognate target pictures in L2 (English) while ignoring auditory distractors in L1 (French) and L2. Taken together, our results demonstrated that lexical representations from L1 are active and compete for selection when naming in L2, even in highly proficient bilinguals. However, the extent of cross-language activation was modulated by both word-type and individual differences in inhibitory control capacities.

Bilinguals have been shown to outperform monolinguals at suppressing task-irrelevant information and on overall speed during cognitive control tasks. Here, monolinguals’ and bilinguals’ performance was compared on two nonlinguistic tasks: a Stroop task (with perceptual Stimulus–Stimulus conflict among stimulus features) and a Simon task (with Stimulus–Response conflict). Across two experiments testing bilinguals with different language profiles, bilinguals showed more efficient Stroop than Simon performance, relative to monolinguals, who showed fewer differences across the two tasks. Findings suggest that bilingualism may engage Stroop-type cognitive control mechanisms more than Simon-type mechanisms, likely due to increased Stimulus–Stimulus conflict during bilingual language processing. Findings are discussed in light of previous research on bilingual Stroop and Simon performance.

A visual Simon task was used to study the influence of aging on visuospatial attention and inhibitory control processes. Responses were much slower for elderly than for young participants. The delay in trials in which stimulus and response side did not correspond as compared to when they did correspond (the Simon effect) was larger for older people, even after correcting for general slowing due to aging. The slowing of responses reflected a slowing of internal processing, as indicated by progressively larger delays of the peak latencies of the N1, the posterior contralateral negativity (PCN), and P3. A comparison between the amplitudes of the PCN and early lateralized readiness potential (pre-LRP) indicated that transmission from posterior sites (PCN) to the motor cortex may be affected by age. The data support the view that aging affects an inhibitory process that controls direct visuomotor transmission.