The young woman sitting alone near the front of the MAX train car was speaking passionately, presumably to a friend on a cellphone. Nothing new—we overhear all sorts of conversations these days. But then, unexpectedly, she lifted a blue bundle to her face, and it became clear that she was talking to her infant son. Some assumptions, thankfully, are so wrong.

Somewhere, she had learned how important it is to talk to her baby. Although her son didn’t understand the meaning of most of her words yet, he was certainly learning the sounds of English, and more importantly, he was learning that he was part of the conversation.

Conversational experiences during babies’ first 36 months figure decisively in the development of oral language. Research by the University of Chicago’s Janellen Huttenlocher shows that language growth is clearly linked to the extent that children’s parents talk to them. By the time they’re two years old, children of parents who often speak to them have five times the amount of vocabulary as those whose parents seldom speak to them.

It’s really that simple. Children learn the words they hear. The more parents and caregivers talk and read to their babies, the more rapidly their young ones’ vocabularies develop. In fact, most vocabulary is acquired incidentally—that is, in the context of daily family life. Research by the University of Kansas’s Betty Hart and Todd Risley found that 86 to 98 percent of the words in a three-year-old’s vocabulary consisted of words that were also present in their parents’ vocabulary. As expected, children mirror their parents’ language style and the frequency of interactions, too.

Surprisingly though, Hart and Risley’s research also reveals that the amount of conversation in the home correlates positively with a family’s socioeconomic status. The higher the family’s income, the more language interactions are heard. The lower the family’s income, the fewer the language interactions. At age six, children from professional families had a 20,000-word vocabulary and children from welfare families had a 3,000-word vocabulary.

Considering that the most crucial time in the development of children’s oral language skills is from birth to three years old, this word gap puts children from lower socioeconomic backgrounds—or any child who is not frequently involved in family conversations—at a serious disadvantage at the very beginning of school. And according to the National Reading Panel’s 2000 report, “Teaching Children to Read,” when words are not in children’s oral vocabularies, they have trouble reading the words and their comprehension is hindered.

It’s more than just the quantity of words, though. The quality of parent talk matters, too. Higher-income families use more encouragements and explanations, while lower-income families tend to use more straightforward directives and prohibitions that offer children fewer opportunities for learning rich language. And as studies have shown, the negative association between poverty and verbal language skills persists throughout the school years.

But learning to talk and read is all about language and social interactions, not income. Parents of every income level can enhance their children’s oral language skills by asking open-ended questions, building on what their children are saying, using descriptive words, and relating the conversation to their youngster’s experiences and feelings—all while doing the laundry. These strategies are especially effective for children under the age of three, which means that parents should be conversing with their children long before their young ones are conversant!

For some parents, talking to their children before they can talk can be intimidating or embarrassing. That’s why it was such a delight to hear the young mother sharing her plans with her baby. Her son didn’t utter a word in reply, but be assured that he understood more than she knew! Babies know a lot more than they can tell us, and knowing that means we need to chatter meaningfully, if not endlessly.