Child-directed speech (CDS) shows similar characteristics across many languages, but is known to vary across cultural anddemographic groups (Lieven, 1994). Is CDS consistently discriminable from adult-directed speech (ADS) despite thesedifferences? Perhaps: adults listening to scripted female CDS can discriminate ADS-vs-CDS in a language they dontspeak (Bryant et al., 2012). We build on this finding by asking North American English speakers to classify utterancesfrom the natural language input of 10 Tseltal Mayan children as ADS or CDS (n = 1836 utterances). Binomial mixed-effects regressions of accuracy show that listeners are more accurate on utterances from females (mFemale = .81, mMale =.67) and adults (mAdult = .82, mChild = .72), with a larger gender effect for child speakers (m: Girl-Boy = 0.31, Woman-Man = 0.09). This suggests that (a) ADS-CDS discrimination of natural speech in an unrelated, non-familiar language isreliable (mAll = 0.78) and also (b) modulated by speaker type.