6 THE HUMAN ORGANISM
6E) PHYSICAL HEALTH
Germs. Elementary-school students may have the following ideas about germs: Germs are microorganisms causing illness; germs enter the body through the mouth while eating and leave the body through the mouth; every illness is caused by germs; all diseases are caused by the same kind of germ; the process of infection is automatic; any infection in the body necessarily makes it ill; and when medicine is administered, healing takes place immediately (Nagy, 1953). (This admittedly dated study is still cited by many authors.)
Causes of illness. Lower elementary-school children may think that illness is the result of misbehavior and realize that they are ill only when they are told that they are by others or when their illness has a behavioral impact, such as having to stay in bed or to go to the doctor. Upper elementary-school children may believe that all illnesses are caused by germs and are contagious. As students grow older, their beliefs about causes of illness begin to include also the malfunctioning of internal organs and systems, poor health habits, and genetics. Upper elementary students can understand that a change in internal body state or the experience of symptoms is the consequence of illness (Hergenrather & Rabinowitz, 1991).
Health. Students of all ages focus on the physical dimensions of health and pay less attention to the mental and social dimensions. Students associate health primarily with food and fitness (Brumby et al., 1985; Moon et al., 1985). Middle-school and high-school students' wrong ideas about the causes of health and illness may derive from cultural knowledge (Rice, 1991; Prout, 1985).
Students of all ages tend to believe that many factors they consider important to their health and life span are also beyond their personal control (Brumby et al., 1985; Merkle & Treagust, 1987). After instruction, middle-school students appear to have accurate knowledge about nutrition and physical fitness, but they are often unable to explain their knowledge in scientific terms (Merkle & Treagust, 1987).
Nutrition. Lower elementary-school children know that there are different foods, that there are good foods and bad foods, and that there are different nutritional outcomes such as variations in size and health. In addition, they are aware of certain limits (drinking just water leads to death; eating only one thing--even one good food--is insufficient for good health). They still may believe, however, that food and water have equivalent nutritional consequences; height and weight are similarly influenced by amount of food eaten; and energy and strength result from exercise but not nutrition. These misconceptions tend to fade by the end of 5th grade (Wellman & Johnson, 1982).