Portuguese is the fifth most spoken language in the world, with more than 250 million speakers worldwide. Aside from its country of origin, Portuguese is the official language of Brazil, Mozambique, Angola, Cape Verde, Acores, Guinea-Bissau, and São Tomé and Príncipe, and is commonly spoken in seven other countries. A part of the Ibero-Romance language group that descends from Latin dialects, its origins are ancient, but during the Age of Exploration, it spread to many corners of the globe, and is present in many popular forms of music, such as bossa nova and samba.

As people age, cognitive flexibility — the ability to adapt to unfamiliar or unexpected circumstances — and related "executive" functions decline. Recent studies suggest lifelong bilingualism may reduce this decline — a boost that may stem from the experience of constantly switching between languages. However, how brain activity differs between older bilinguals and monolinguals was previously unclear.