My Second Son's Language Development

My second son, Cory, was born in the winter of 2017. Like my first son, we tracked his language development to see how fast he picked up the various languages that our family speaks.

The Data

The data was collected in the same manner as last time. The only difference was I added a new language category for “animal sounds” because when recording that data for Theo I realized it was hard to tell “moo” from “mu”. A catch-all category for animals made data logging much easier.

I had the same data collection difficulties as last time: when Cory was young, it was hard to decide if he was associating a sound with a concept. When Cory was older, he was so good at imitating sounds that it was hard to know if he knew the word or was just repeating what you had said. There was a new difficulty this time as well: we had our third child just as Cory’s language development exploded. Cory was with his grandparents for a few weeks as we adjusted to the new baby and so I was not able to record his new words during that time period.

You can find the Jupyter notebook used to perform this analysis here (rendered on Github). The data can be found here.

Development

Cory’s first baby sign was waving goodbye at 11 months. He learned four more—pointing at things he wanted, blowing kisses, shaking his head for “no”, and shaking his hands for “all done”—before speaking his first word. His first word, like his older brother, was in Cantonese, although it was “dad” and not “dog”. It was two more months before he said “mom” in Cantonese, at which point he already knew “older brother”, “ball”, “there”, and “pick me up”. My wife was disappointed it took so long, but I suspect it was because he spent so much time with her he did not need a word to get her attention, he always had it.

Cory’s sign language development outpaced his other languages until he was 20 months old. My suspicion is the same as it was with his brother: sign was his universal language. English could only be used to talk to dad, Cantonese could only be used to talk to mom, but sign could communicate with both of us and even his grandparents.

Cory’s language development is plotted below, showing the number of words he could speak in each “language” as a function of how old he was.

A plot showing the number of words my second son could speak as a function of age.

Cantonese and English exploded at about 19 months; Cory doubled his vocabulary in those two languages in just four weeks. He almost doubled it again in his 20th month. In his 22nd month, he picked up about 50 Cantonese words and almost 70 English ones!

Part of that growth in the 22nd month is a data entry artifact: that is when he went to stay with his grandparents. He had a week to learn words and I only recorded them when he came back to us and spoke them. You can see two flat areas in his English and Cantonese language development—one right before 22 months and one right after—that are due to this effect.

Spanish started pretty slowly because only my father speaks it to him. At 22 months we moved closer to my parents so Cory spent more time with them. You can see a bit of an increase in the amount of Spanish learned then; I’m sure we would see a much larger increase if we kept recording.

The Words

I plotted a selection of some of Cory’s first words in each language below. Notice that I have switched to a log plot for the y-axis to better show the beginnings of each language.

A plot showing the first words my second son could speak as a function of age.

A few fun words:

Of course, now that I have two datasets I can compare how both boys developed. Look for those posts in the near future!


Updated : I have added a link to the post comparing the development of Theo and Cory.