One of the coolest moments for a parent of a young child is when you finally can have a conversation with your kid. Those first conversations are humbling – and often hilarious - to experience.
By the end of the second year of life, most children are putting together simple sentences. The first sentences children speak are “telegraphic speech,” called such because the nonessential parts of the sentences are missing. These early sentences clearly communicate something, but are simple: “Eat now.” “More swing.” “I go.” Although these sentences are simple because of the number of words they include, children often display many aspects of language in them (i.e., pronouns, verbs, nouns) and also tend to demonstrate a quickly growing vocabulary. The two-word combination seems to be a clear part of language progression, with children moving through this sentence phase regardless of the language they speak. By 2.5 years of age, most children have 4-word sentences and grammatically these sentences are complicated, often including more than one clause (“I want to ride my bike because it is sunny.”; “Can I do it when I get home?”). 
These increasingly complicated sentences are great for two reasons. First, because your children are going to make adorable errors. And second, because the conversations are endearingly one-sided.
First up. Adorable errors.
In early childhood, children learn the basic grammatical rules of their language. And they make mistakes along the way. My favorite part of this is a phenomenon called over-regularization. Basically, this is when children learn the grammar rules and over-extend them, applying them to irregular words. For example, the general grammar rule of English is that past tense is achieved by adding an “ed” on the end of the word. Laugh becomes laughed. Hop becomes hopped. Climb becomes climbed. But some words are irregular. For example, run becomes ran. Go becomes went. In early childhood, children apply the learned grammar rule to everything, not yet knowing the exceptions. So up until 4 years of age or so, it’s not uncommon for children to say “runned” and “goed.” The child has correctly mastered the grammatical rule, but is applying it to words that are exceptions to the rule. It is so stinking cute when they make the mistake in their little toddler voices.
Most interestingly, children usually start out saying the word correctly, but as they come to understand grammar rules, they begin to use them – and then they make the mistake. We don’t really know how children come to understand the exceptions to grammatical rules; it is not a process that seems to come from parent’s interactions or language communication. Instead, it’s likely that cognitive changes allow for children to become more flexible in their application of the language rules. Scientists are still working to understand this process.
Second up. One-sided conversations.
Ever notice that your child spends most of their time talking to him or herself? Even while playing in a group or talking to a parent or caregiver, as much of half of a child’s speech is directed at him or herself. Some theories of child development think that this “private speech” helps children regulate and plan their own behaviors. Over time, children move this self-talk into their head, as their ability to mentally plan increases.
When children aren’t talking to themselves, they are working on other sorts of skills. Like, how to talk about the same thing with a conversational partner.
When children talk to other children, at least at first, they are often not talking about the same thing. Instead, both children are having their own little egocentric stream-of-consciousness chat.
Child 1: “I have a green bike.”
Child 2: “Peanut butter sandwiches are amazing!”
Child 1: “My bike is super fast.”
Child 2: “I like to eat peanut butter on pancakes, too.”
The children are next to each other, talking to each other, but just not talking about the same thing. From 2 to 3 years of age, children increasingly respond to what the person they had just talked to said, but still up to 60% of the conversation is unrelated and mostly to themself. 
This is why conversations with young children are so endearing.
Across the preschool years, children increase their ability to take the perspective of the other person. This cognitive advantage allows the child to infer actual meaning and interests of their conversational partner, ultimately allowing for a conversation on the same topic.  Some of that involves being able to understand emotion in a voice. By 3 or 4 years of age, most kids can understand intention by the emotion of the speaker. In a very creative study, researchers showed children a broken doll and an intact doll. When the researcher said, “Look at the doll,” in a sad voice, the children looked at the broken doll. When they said the same phrase in a positive voice, children looked at the intact doll.
Between 3 and 5 years of age, children’s conversations continue to improve and children become much better about talking about past events. Part of the reason for this improvement is that children have a better understanding of how to tell stories – the structural properties of it. But it’s also true that parents and caregiver play a role in this. We do so by scaffolding. Scaffolding is when parents ask questions to help their child fill out a story.
Parent: “Tell your teacher about your weekend. What did we do?”
Child: “I don’t know.”
Parent: “We went to a party – do you remember the party?”
Child: “Oh yeah.”
Parent: “Did we do something special at the party?”
Child: “I got a butterfly painted on my cheek.”
Parent: “That’s right! Did we eat something special?”
Child: “We ated the cake and singed a song.”[a]
The parent in this conversation is working really hard to help their child communicate a story to their teacher. These sorts of interactions seem to be invaluable to helping a child learn how to tell stories.
Turns out, parents who do more of this, by asking probing elaborative questions, have children who produce better storytelling later on.  So it’s important to help teach your child how to tell stories.
It really boils down to the fact that if we want our children to be able to communicate well, we really have to take time to talk with them. This is why family experiences can be so powerful. Play time and meal times where an adult is communicating with a child can help a child have better conversational skills. Take time out of each day to make sure you really talk to your kid. This doesn’t mean asking them how their day went – I can guarantee that this question is going to be a dud well into the teen years. Instead, ask them what they think about something like recess, broccoli, bikes, or Halloween costumes. It doesn’t have to be anything formal, but simply asking your children questions about their ideas will often elicit a response that will give you more to work with when trying to build a conversation. The hard work when your child is young will pay off. It leads to a skilled conversationalist in the school years, which will serve your child well. It also means you’ll have a good foundation of talking to your child, which is going to come in handy for the rest of your lives together.
[a] Seriously. How cute are those errors of over-regularization?
 Bowerman, M. (1979).
 Bloom, L., Rocissano, L., & Hood, L. (1976).
 Nilsen, E. S. & Graham, S. E. (2009).
 Berman, J.M.J., Chambers, C. G., & Graham, S. A. (2010).
 Reese, E. & Fivush, R. (1993).