Phase 6 — 12 to 24 months

Independent walking frees the hands and the brain. Vocabulary jumps from 1-3 words at 12 months to 50-300 by 24 months, with the first two-word combination ("daddy water", "more ball") around 18-20 months. This is the phase when the baby becomes a child — and when the adult must hold firm limits calmly, without giving in to tantrums or responding with aggression.

Expected milestones

At 15 months

• Walks alone without holding on
• Says 3-5 words with consistent meaning
• Points to request and to show
• Imitates everyday gestures (sweeping, talking on the phone)

At 18 months

• Walks steadily, climbs stairs with support
• Vocabulary of ~10-25 words; understands far more than she says
• Plays simple pretend ("feeds" the doll)
• Recognizes parts of her own body

At 24 months

• Runs, kicks a ball, climbs and descends stairs with support
• Vocabulary of 50-300+ words; combines two words
• Follows two-step commands ("pick up the ball and give it to me")
• More elaborate symbolic play; starts parallel play near other children

Priority practices

• Conversational turns matter more than volume. Romeo's MIT research shows that the number of conversational turns (back-and-forth), not total word count, predicts brain activation in language areas^{Romeo et al. 2018}. Pause. Wait for her to respond with sound, gesture, or word. Respond as if it were full speech.
• Expand, don't correct. When she says "doggy!", respond "yes, the doggy is running!". Adding 1-2 words to her speech is the most validated technique to accelerate language.
• Daily dialogic reading. Use the PEER technique — Prompt, Evaluate, Expand, Repeat^{Whitehurst et al. 1988}. Books with flaps, textures and few words per page work better than long plots at this age.
• Screens are still "no" as a rule. WHO and AAP maintain zero-screen recommendation before age 2, with the exception of video calls with family^{WHO 2019AAP 2016}. What looks "educational" rarely is at this age — the brain needs 3D, hands, and human voice.
• Vitamin D continues: 600 IU/day. Brazilian and US pediatric guidelines raise from 400 to 600 IU starting at 12 months^{SBP 2024}.
• Firm limits with a calm voice. Tantrums are neurological, not manipulation — the prefrontal cortex is still under construction. Name the feeling ("you're angry because you wanted more"), hold the limit, and offer co-regulation (lap, breathing together).
• Safe autonomy. "I do it!" is the phrase of the phase. Let her choose between 2 options (blue or yellow shirt), try the spoon, climb the step. The frustration of trying is the engine of development.
• Bilingualism: window still open. If more than one language is native to a caregiver, OPOL (one parent, one language) has the most evidence^{De Houwer 2007}. Bilinguals may show apparent "delay" until 30 months and then catch up — no cognitive harm.

What to avoid

• Screens as a babysitter during meals or tantrums (becomes reinforcement of emotional avoidance)
• Physical punishment or shouting during tantrums — her emotional brain is still forming, copies what it sees
• "Growth" or "appetite" supplements without pediatric indication
• Comparing milestones with other children — the normal range is very wide at this age