At its most fundamental level, development involves change. This change must be cumulative and systematic; random change is not considered to be developmental in nature. Whereas the concept of growth refers to the addition of new components or skills through the appearance of new cells, development refers to the refinement, improvement, and expansion of existing skills through the refinement of cells already present (Schuster, 1992). More specifically, three basic criteria must be met before change can be considered to be development:

  1. The change must be orderly—not random fluctuations of behavior.
  2. The change must result in a consistent modification in behavior.
  3. The change must contribute to a higher level of functioning in the individual.

When a specific change in behavior satisfies these three criteria, development has occurred.

Development may be either qualitative or quantitative. For example, increases in height, weight, creativity, activity level, and vocabulary are quantitative changes; that is, they are directly measurable. Progression toward maturity and the integration of complex physiological and psychological processes are qualitative changes; in other words, it is more difficult to gain an exact measure of these changes, but the changes are still noticeable. We see both types of change when children’s shoes no longer fit, when they run faster and jump higher, when their increased proficiency in language helps them control their surroundings and their behaviors in a more accomplished manner, and when old toys and games lose their fascination in favor of new friendships and increased social contacts.

With these definitional components in mind, it also becomes important to distinguish between development and maturation. The concept of maturation is similar to that of development in that skills and functions are refined and improve over time. The concepts differ, however, in that maturation refers to the unfolding of personal characteristics and behavioral phenomena through the processes of growth and development. The concept of maturation reflects the final stages ofdifferentiation of cells, tissues, and organs in accordance with a genetic blueprint wherein full or optimal development of a specific skill can be achieved (Schuster, 1992).