Approach/Withdrawal measures an infant's initial reaction to a new food, person, experience, or situation. Approaching infants tend to have a positive first reaction. Children who are very approaching are often also very active; they may barrel into new situations, sometimes intimidating other children, and may benefit from some help in learning to slow down a bit. Withdrawing children have a negative first reaction, though they may warm up in a short time if the experience isn't forced on them. It's important to remember that the tendency to withdraw is an initial reaction. If given gentle encouragement and the time to assimilate, these children may become the life of the party. But when they're rushed or pushed, they may become extremely resistant.
Adaptability measures a child's adjustment to changes and transitions after their initial reaction to them. Infants who are high in adaptability are the ones you can take anywhere. They can sleep anywhere and handle disruptions to their routine well. Highly adaptable children do well with changes and transitions--which tends to make them easygoing. Often very tractable and undemanding, they may need help learning to stand their ground. Parents and teachers who are busy with squeakier wheels sometimes need to make a conscious effort to spend more time with adaptable children.
Low-adapting children, like my son, react negatively to transitions and need much more than the 20 minutes a withdrawing child might need to settle in to a new situation. Almost all children will have some difficulty adjusting to big changes, such as the birth of a sibling, a move to a new neighborhood, or attending a new school. But children low in adaptability also have difficulty with day-to-day changes and transitions. An unexpected meal change or an unplanned stop for errands can lead to big negative reactions. They cope with their discomfort by resisting change, and they may insist that every detail of daily routines be followed exactly the way they want them done. Their resistance to change is an aversion to novelty, any novelty; they may be as resistant to going to a party as they are to seeing a doctor.
Children low in activity and low in adaptability tend to be very transparent in their resistance to change, engaging in clinging behaviors, such as hanging on to a parent's leg or hiding behind them. Children low in adaptability and highly active may have a high enough appetite for life that they seem initially fine or even eager about changes (approaching), but may be resistant or suffer a meltdown after getting beyond the initial excitement. Low-adapting children, especially if they aren't high in intensity or activity, know their comfort zones. They're unlikely to follow along just because everyone else is doing something. Giving low-adapting children a finite choice--tooth brushing or hair brushing first, for instance--helps to make them feel more in control.