Reinforcement of vocalizations through contingent vocal imitation.

Pelaez et al. (2011) asked moms to copy every sound their baby made. The babies were under two years old and had developmental delays.

The researchers switched back and forth: sometimes mom imitated right away, sometimes she stayed quiet. They counted how many sounds the babies made in each phase.

When moms copied the sounds, ten out of eleven babies started making more sounds. When moms stayed quiet, the sounds dropped.

The copy-cat move worked like a reward. It was simple, free, and fast.

Sun et al. (2025) later ran a tighter test with four control conditions and saw even bigger gains. Their newer data now sets the gold standard, but the core trick—copy the child—stays the same.

Neimy et al. (2020) moved the same tactic into living rooms with babies at risk for autism. Moms added sing-song “motherese” while they imitated. Vocal rates tripled, showing the trick works at home, not just in labs.

Hickey et al. (2024) proved you can teach parents the tactic in twenty minutes with a short online video. Parents copied more, and their babies vocalized more, closing the loop from lab to couch.

You can use this today. When an infant or toddler makes any sound, echo it right away. Do it during diaper changes, snack time, or play. No toys or tokens needed—your voice is the reinforcer. If you train parents, show a quick clip and send them home to practice. More early sounds now can mean stronger words later.