Adults change in predictable ways according to age, individual characteristics, and demands of the environment. Glickman has found that cognitive, social, and language development don't end with adolescence or early adulthood, but continue throughout life. Research on aging and learning has identified two categories of intelligence, one that increases during adulthood, one that decreases. These learning categories should be taken into account in planning program presentations. In the cognitive area, the decline of the nervous system accounts for the slowing of abilities to handle instant and visual information.
Older people have extensive experience and knowledge to use.
An older person may not be able to respond quickly, but can relate experiences to an understanding of new problems. Individuals experience various stages of conceptual development as they grow. Most adults develop to the stage of understanding through the authority of others and never get past this conventional reasoning stage. Thus, most education for adults is to an audience made up of people respecting authority and making decisions around that principle. Concept development is important when understanding the learning level of participants in Extension education programs.