Let's not forget about language proficiency and cultural variations while linking bilingualism to executive control

Valian (2014) argues that current approaches in the study of bilingualism's beneficial effects on executive functions and cognition are at best methodologically weak. There is no unanimity on what constitutes executive function and which tasks measure it. I agree with her view that executive function is not a single phenomenon but a collection of processes. Different tasks measure different aspects of them. Performance on different executive function tasks is related to the particular cognitive demands of the tasks as well as the participants’ profile. It does not follow necessarily that negotiating two languages should lead to an enhancement of ability on that task. Therefore, no single task can capture the cognitive benefits of bilingualism. Valian proposes that factors such as education, socio-economic status, and even extracurricular skills involving sports and exercise could boost executive functioning independent of bilingualism.