By Matthew Hutson, published on September 1, 2008 - last reviewed on December 28, 2011
Languages learned before the age of 5 are represented differently in the brain than are later languages. For example, they trigger sensory associations more actively. Researchers can detect the native tongues among highly proficient bilinguals simply by monitoring neural activity as subjects read.
Learning a second language can help you out decades down the road. On average, lifelong bilinguals incur dementia four years later than others, adding to the evidence that lifestyle can be more neuroprotective than drugs.
Don't worry if Johnny loses some English vocab on his trip to France. Research finds that it's not from atrophy of the old tongue; the new one is running interference. To better learn new labels for things, the brain suppresses previously learned terms.
Infants as young as 4 months can tell when a speaker switches languages just by watching the mouth—a marker of how important visual cues are to language learning. But by 8 months only babies raised in bilingual households have this ability; without continued exposure, some perceptual abilities wane.
Cultural cues such as national flags can trigger different values and even different elements of your personality. Language acts as one cue: Researchers find that Spanish-English bilinguals are more assertive and achievement-oriented when using English, which seems in line with American culture.
Babies in bilingual households are slow to develop the ability to discriminate subtle differences between similar-sounding words such as "bad" and "dad." Instead, they devote attention to the meanings of words in their expanding vocabularies.