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You might be able to mimic a Spanish accent while doing your best Antonio Banderas impression, but completely shedding your native accent in favor of a new one is much more difficult. The way you speak today is likely the accent you will have for the rest of your life.
As noted by Smithsonian, our accent begins to form as early as 6 months old—shaped by the pronunciation rules of a language influenced by factors like geography, culture, and social class. When babies are learning words like nap, dad, and play, they're also absorbing the sounds and pronunciations from those around them. Newborn brains are wired to learn languages simply through exposure. By the time they begin speaking, they already know the proper pronunciations for their native language or languages.
As you grow older, your ability to recognize and adopt foreign accents and languages diminishes. For example, if you're an English speaker from Boston, you might find someone from Dallas speaking English to sound "off," even if you can't pinpoint exactly what makes it different. This is one reason why mastering a foreign accent can be challenging, even after hearing it many times.
By around the age of 18, your capacity to learn a second language experiences a significant decline. The same might apply to adopting a new accent. While spending time in a foreign environment could help you pick up some elements of the local accent, fully switching to a non-native accent without actively working to keep it is highly unlikely as an adult.
There is an exception to this, however, known as Foreign Accent Syndrome. After a head injury or stroke, some individuals have unexpectedly started speaking with accents they never used before. This syndrome is extremely rare, affecting only about 100 people worldwide, and medical professionals are still unsure of the exact cause. Though the individuals may sound different, they aren't necessarily speaking in foreign accents as most would imagine; instead, it could be subtle changes in how they move their jaw, tongue, lips, and larynx, affecting the pronunciation of certain vowels.
