Assimilation is best described as adaptive articulatory changes causing a speech sound to become similar to a neighboring sound segment.

• A. A change that increases contrast between sounds
• B. Adaptive articulatory changes causing a speech sound to become similar to a neighboring sound segment
• C. A change in pitch contour
• D. A random variation in timing

Answer: (B)

Assimilation happens when a sound shifts its articulation to become more like a neighboring sound, due to the fluid way our speech organs move in connected speech. This is coarticulation in action: one sound influences the place, manner, or voicing of an adjacent sound so they become more alike. For example, the nasal in a phrase like “input” often moves from an alveolar n to a bilabial m before the following bilabial p, so you hear [ˈɪmpʊt] rather than [ˈɪnˌpʊt]. This shows how the articulators adjust to nearby sounds, producing a sound that matches its neighbor.

The other descriptions don’t capture that adaptive, neighboring-sound influence. Changing pitch contour relates to intonation, not the segmental articulation of neighboring sounds. Random variation in timing is about timing, not how sounds become more similar. And a change that increases contrast would do the opposite of assimilation by making sounds less alike.