I have three toddlers (16-27 months). The oldest started responding no around 18-20 months. Yes didn’t come along until almost 2. My daughter (17 months) can say yes and shake her head for no, but it’s a skill that comes and goes. The 16 month old just recently started shaking his head no and will do so occasionally. From everything I’ve read it’s not a big red flag until closer to maybe 2.5.
Repeating words is a form of imitation which is very important to language acquisition. I would take that as a positive sign at least at this point
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