That mistake is a sign of genius. No adult ever said "goed." The child worked out a rule (add -ed for the past) and applied it everywhere, even where English breaks its own rule. Children don't copy language. They rebuild it from scratch.
It starts before birth
Hearing works in the last months of pregnancy, and babies come out already tuned in.
- In a 1980 study, newborns could choose which recording they heard by sucking on a dummy in different patterns. They worked to hear their own mother's voice over another woman's.
- A 2009 study recorded the cries of 30 French and 30 German newborns, only a few days old. The French babies mostly cried with a rising melody and the German babies with a falling one, matching the typical melodies of each language. They were already "speaking" with an accent.
The first year: from citizens of the world to locals
Every language uses a different set of sounds. Hindi tells apart two "t" sounds (one with the tongue against the teeth, one with it curled back) that English speakers hear as one. Japanese doesn't separate English "r" and "l."
Young babies can hear almost all of these differences, in any language. Then, between about 6 and 12 months, they tune out the contrasts their own language doesn't use and get sharper at the ones it does. Linguists call this perceptual narrowing. A baby in Tokyo and a baby in Toronto start with the same ears and end the first year with different ones.
A newborn can learn any of the world's 7,000-plus languages. By their first birthday, they're already specializing.
Here is the most striking experiment in the field. In 2003, Patricia Kuhl's team gave 9-month-old American babies twelve short sessions with a Mandarin speaker who played and read with them. Afterwards the babies could still hear a Mandarin sound contrast that babies their age normally lose. Another group got the same Mandarin speakers and the same material, but on video or audio only. They learned nothing. For babies, language learning seems to need a real, responsive person.
The rough timeline
These are typical patterns, and the range of normal is wide.
| Age | What usually shows up |
|---|---|
| Newborn | Prefers mother's voice and the rhythm of the home language |
| ~4 months | Cooing ("oooo," "aahh"), and making sounds back when you talk |
| ~6–9 months | Babbling with consonants: "bababa," "mamama" |
| ~12 months | First words or word-like names ("mama," "dada"), waving bye-bye, understanding "no" |
| ~18 months | Several words beyond "mama" and "dada"; follows simple one-step directions |
| ~2 years | Two-word combinations: "more milk," "daddy go" |
| ~3–4 years | Sentences of four or more words, simple answers and stories, and the classic overgeneralizations ("goed," "foots") |
How do they do it?
Two big ideas have competed for decades, and the honest answer is that the debate isn't settled.
Built-in grammar. Noam Chomsky famously argued that children hear too little, too messily, to work out grammar from scratch, so humans must be born with a mental blueprint for language. (He called this the "poverty of the stimulus.") Supporters often point to Nicaraguan Sign Language. Before the late 1970s, deaf children in Nicaragua were mostly isolated, each using home-made gestures with their families. When new special-education schools brought hundreds of them together from 1977 onwards, the children created a full sign language among themselves, and each younger group of children made its grammar richer and more systematic than the one before.
Learning from use. Researchers such as Michael Tomasello argue that children are extraordinary pattern-detectors and social learners. They don't need a built-in grammar. They need huge amounts of meaningful, back-and-forth communication. Kuhl's video experiment fits this view well: the information was the same, but without a social partner it didn't stick.
Many researchers now take a middle position. Children bring powerful learning abilities to the job, and those abilities need a rich, social stream of language to work on.
The "wug test": proof they learn rules
In 1958, the psychologist Jean Berko Gleason showed children a drawing of a made-up bird-like creature. "This is a wug. Now there is another one. There are two of them. There are two ___." Young children happily answered "wugs," a word they could never have heard before. They hadn't memorized plurals one by one. They had learned the rule.
What actually helps
- Talk with them, not just near them. Respond to babbles as if they were conversation. Take turns. Name what they're looking at.
- Use "parentese" freely. The sing-song, slower, higher-pitched way most adults instinctively talk to babies is not silly. Babies prefer it (a 1985 study found four-month-olds chose to listen to it), and it exaggerates the sounds they need to learn.
- Read together. Picture books bring words you'd never use while making lunch.
- Don't fear two languages. People once worried that bilingual children would be confused or delayed. Research has not supported that. Bilingual children reach the main milestones within the normal range, as long as you count the words they know in both languages together. Mixing languages in one sentence is a normal stage, not a problem.
- Screens are not a substitute. Given the video result above, a show is no stand-in for a person who talks back.
The "word gap," with care
You may have heard that poorer children hear "30 million fewer words" by age three. That figure comes from a 1995 study by Betty Hart and Todd Risley, which recorded 42 Midwestern American families for an hour a month over two and a half years. It became hugely influential, but it was small, and it counted only speech aimed straight at the child by the main caregiver. A 2018 study by Douglas Sperry and colleagues in five American communities found huge variety within every income group. Once it counted all the talk a child could hear, including other relatives and overheard conversation, it did not find the 30-million-word gap. The useful lesson survives: talk with children a lot. The scary number does not.
The takeaway
Children learn language by actively working out its patterns, not by copying. They start before birth, tune into their own language's sounds during the first year, and rebuild grammar rules for themselves, which is why they say "goed." Scientists still debate how much is built in and how much is learned, but everyone agrees on what helps: lots of real, responsive, back-and-forth talk with real people. Two languages are not too many, and a screen is not a conversation partner.
Try this: if you have a baby or toddler in your life, spend ten minutes today narrating and taking turns. Pause after you speak and treat whatever sound they make as their reply. If they're older, try the wug test with an invented word and see the rule appear.
A note on development: children vary a lot, and late talkers often catch up. But if a child isn't babbling by around 9 months, isn't trying to say three or more words by 18 months, isn't putting two words together by 2 years, or loses skills they once had, talk to a doctor or health visitor and ask about developmental screening. Acting early is never wasted. In the US, the CDC's "Learn the Signs. Act Early." program has free milestone checklists.
Sources & Further Reading
Sources
- DeCasper & Fifer, "Of human bonding: newborns prefer their mothers' voices," Science (1980). Mampe et al., "Newborns' cry melody is shaped by their native language," Current Biology (2009): 30 French and 30 German newborns.
- Perceptual narrowing between about 6 and 12 months: Werker & Tees (1984, reprinted 2002) and Kuhl, Tsao & Liu, "Foreign-language experience in infancy," PNAS (2003), the source of the live-versus-video Mandarin experiment (9-month-olds, 12 sessions).
- Milestones: US Centers for Disease Control and Prevention, "Learn the Signs. Act Early." checklists for 4 and 9 months, 1 year, 18 months, and 2 and 4 years.
- Wug test (1958): Wikipedia, "Jean Berko Gleason." Nicaraguan Sign Language (schools from 1977; over 400 pupils by 1983): Wikipedia, "Nicaraguan Sign Language." Fernald (1985), "Four-month-old infants prefer to listen to motherese," via Wikipedia, "Baby talk."
- Bilingual milestones within the normal range when both languages are counted: Wikipedia, "Simultaneous bilingualism" (citing Hoff et al. 2012; Genesee & Nicoladis 2007; Pearson & Fernández 1994).
- Hart & Risley (1995), 42 families; Sperry, Sperry & Miller, "Reexamining the verbal environments of children from different socioeconomic backgrounds," Child Development (2018/2019), via PubMed.
Go deeper
- 📘 The Scientist in the Crib by Alison Gopnik, Andrew Meltzoff and Patricia Kuhl: how babies learn, by three researchers who study it
- 📘 The Language Instinct by Steven Pinker: the case for built-in grammar, told brilliantly
- 🌐 CDC: Milestones by age: free checklists from 2 months to 5 years
- 🌐 Related pieces in this library: Learning a Language as an Adult (this category), and the Developmental Psychology category for the bigger picture of growing up