Which pair of phonemes are among the earliest acquired by English-speaking children?

• A. /s/ and /z/
• B. /r/ and /l/
• C. /m/ and /b/
• D. /ʃ/ and /θ/

Answer: (C)

Early-phoneme development tends to favor sounds that are simple to produce and highly frequent in speech. The pair /m/ and /b/ fits this pattern because both are bilabial, using the lips as the primary articulator, which is easier for babies to approximate. /m/ is a nasal made with the lips closed and air through the nose, while /b/ is a voiced bilabial stop produced by briefly building up pressure and then releasing the lip closure. These sounds show up early in babbling and in early words like “mama” and “baba,” reflecting their accessibility and common use in caregiver speech.

Other pairs involve more complex articulations: fricatives or affricates like /s/ and /z/ require precise narrowing and frication; /r/ and /l/ demand intricate tongue maneuvers to shape the oral cavity; /ʃ/ and /θ/ combine challenging place and manner features. Those complexities generally push their acquisition later.