Human infants seem ready to learn any language, arguing for an impressive array of universal language-learning strategies. However, the end result of learning is clearly not uniform. Languages are different, by definition, because speakers of one language can't understand the other. Do speakers process the languages differently as well? This symposium explores several aspects of this issue, with a focus on smaller, often endangered languages: languages are falling silent at a higher rate than bird and mammal species are going extinct. In the meantime, linguists are exploring indigenous knowledge of remaining speakers to better understand how languages can be so different and yet function in similar brains. Function words such as, "the" and "from" are often lost in agrammatic (Broca's) aphasia; what happens when similar brain areas are affected in a speaker of a language like Navajo, that essentially lacks function words? Is expression easier, or is a different kind of grammatical process lost? How do the typical structures of a language change the way information is presented in a sentence? How different is the soundscape of a language that can distinguish words just by choosing one of five pitches for it? How different are sentence processing strategies in small, unwritten languages from those large, written languages that are typically studied? The symposium explores these issues and highlights the urgency of studying them while we still can.