Q. My son is 8 months old and takes great joy in destroying things. I'll build a tower of blocks; he'll knock them down. Worse, he takes books off his shelf and throws them on the floor. I'm concerned that he's becoming overly aggressive. Should I do something?
A. Even though it may seem like your little boy is a human wrecking ball, he's really just a typical 8-month-old. Children this age don't understand the concept of destruction (or creation, for that matter). What your son is trying to understand is the concept of cause and effect.
By 4 to 8 months of age, babies start to notice that their actions have an impact on objects. Generally, this happens by accident: A baby's random movements bump a mobile or a musical toy, and he notices that the resulting sound or motion is related to the movement he made. This is a marvelous discovery, and he'll want to test it again and again. We all learn by doing -- by trial and error, really -- but children of different ages learn best in different ways. For babies, repetition and predictability are key, and seeing the same thing happen over and over can be educational and thrilling.
Early on, your son's understanding of the relationship between his actions and outcomes was limited. He didn't know, for example, that when he flailed his hands, they hit the blocks, knocking them over and making a noise; he just noticed that his hand motion resulted in sound and movement from the blocks. Over time, and with practice, babies learn which actions result in which outcomes.
By 8 to 12 months, babies start doing things with a specific purpose. Developmental psychologists call these sorts of behaviors "goal-directed chains." This means that your baby can now engage in one action in order to achieve another goal, such as moving a toy to reach something directly behind it. The really exciting thing about this seemingly simple behavior is that it shows that your baby can now anticipate the outcome of his actions. His regular experimentation -- and your patience -- has finally paid off. So don't be concerned that your son has destructive tendencies; instead, be pleased at how well he's developing cognitively. You can even help him by commenting on what he's doing by identifying the causes and effects ("You knocked down all those blocks with your hand! You made a crashing sound!"). Sharing in his delight will please him and encourage him to continue his experimentation and learning with other toys.