All toddlers have their own timetable, but you can watch for certain developments around this time.
Your baby’s brain is growing by enormous leaps right now. By the time a child is 2, the brain has 100 trillion neural connections, or synapses. The results of this synaptic proliferation are most apparent in his motor development, language acquisition, and emerging self-awareness. As the number of synaptic connections peaks, a pruning process—in which synapses that aren’t being used wither away—is also occurring. This editing allows resources to be directed where they’re most needed. Each of your child’s movements, thoughts, and expressions involves a specific set of synaptic connections, which, much like muscles, are strengthened by repeated use. With each skill your toddler masters, whether physical or mental, the brain pathways involved are reinforced, laying a foundation to build on. Here’s a look at some of the ways his brain development is fueling all sorts of new advancements right now.
Have you noticed that your toddler is beginning to use the personal pronouns “I” and “we”? This change is the result of rapid development in the areas of the cerebral cortex responsible for higher-order functions, like self-awareness and self-consciousness. In other words, during this period, cortical growth is providing your child with a stronger sense of himself, one that is separate from the world around him. In addition, neural networks are getting denser and synapses are firing faster in other areas of the brain, such as the frontal and temporal lobes responsible for memory, language, and hand-eye coordination.
At this stage, your toddler can follow simple directions (at least when he’s not saying no!) and is gaining a better understanding of cause and effect. An important aspect of toddler brain development is that despite all your child’s growth, he doesn’t yet have the ability to stop himself from doing something, even when he’s been told not to. If, for instance, he’s pulling the cat’s tail and you ask him to stop, he may not respond as you’d like. That’s because multiple regions of the cerebral cortex are involved in remembering, planning, and controlling impulses, and the synaptic wiring is not yet supporting all these functions.
Memory probably isn’t the first thing that comes to mind when you think about motor development, but it’s an essential element. When your toddler tries something new, like moving his high chair, and then does it again, the repeated experience reinforces certain neural pathways, and the action becomes encoded into memory. Likewise, when he lifts a ball and throws it multiple times, the brain records the physical, spatial, and sensorial components involved in the action; so the next time he goes to throw a ball, he automatically draws on that memory, rather than having to figure out how to do it anew. One reason your toddler has so much trouble sitting still is that he’s busy practicing and reinforcing each new skill—from running, to climbing stairs, to stacking blocks—and that strengthens the neural pathways in the brain involved in those series of motions.
At this point in your toddler’s development, the two hemispheres of his brain—as well as the network encompassing the prefrontal cortex, language areas, hippocampus, and cerebellum—are working together with greater efficiency. This coordination puts your child in the midst of a vocabulary explosion that quadruples the number of words he knows by his second birthday. He’s also becoming adept at using those words, as the multiple brain regions involved in speech reception and production are able to communicate more quickly and efficiently. The prevailing theory is that when your child hears you speak, the signals are processed in an area of the brain called the auditory cortex and then relayed to another brain region associated with word recognition. Once he’s grasped what you’re saying and formulated a response, the required tongue, lip, and throat movements are planned in yet another region of the brain. From there, signals are passed to the motor cortex, which sends commands to the required muscles.
Intensified connectivity between the brain’s two hemispheres, along with the maturation of the prefrontal cortex and cortical-subcortical network, brings about greater self-awareness and a sense of individuality. You’ll notice your child beginning to distinguish his own feelings, desires, and intentions from those of other people. Gradually, the limbic system (the seat of your child’s strong emotions and impulses) and the prefrontal cortex (where memory, planning, anticipation, and impulse control take place) will work together in a more integrated way, allowing for increasingly more successful social interactions.