The purpose or reason for why a child engages in a particular behavior. Behaviors typically serve two functions: (1) positive reinforcement (to gain something like attention, a preferred activity, or sensory input), and (2) negative reinforcement (to avoid something like attention, non-preferred activities, or sensory input). For example, biting may serve different purposes for different children. Some children may bite because they want to play with someone but don’t know how to get their attention, to communicate that they don’t want someone to touch their toy, or because their teeth hurt and they want relief. Understanding why a child is biting can inform ways to set up the learning environment to reduce the potential occurrence of the behavior, the type of intervention needed to teach the child a more appropriate replacement behavior, and appropriate consequences to reduce the occurrence of the challenging behavior (i.e., to not reinforce it, such as providing the child with attention if the function of the behavior is to seek attention).