"What are food and air like inside our bodies?": Children's thinking about digestion and respiration

A series of five experiments evaluated whether young children are aware of biological transformations associated with eating and breathing. In Experiment 1, children aged 4, 5, 7, and 8 years predicted that biological damage results from lack of eating and breathing. Children also recognised that food changes inside the body, but seldom referred spontaneously to biological transformation. In Experiments 2 and 2A, children were presented with several alternative explanations of what food and air would be like inside the human body. Both preschoolers and elementary schoolchildren assumed that air would acquire warmth and colour inside the body. The older children consistently understood biological transformation of food. Preschoolers accepted the idea that food undergoes a transformation necessary for health and growth, but did not think so when the transformation was expressed in a material sense. In Experiments 3 and 3A, some preschoolers predicted the transformation of resources inside familiar and unfamiliar living things, but not inside nonliving things. In addition, some 4- and 5-year-olds recognised the sun's contribution to "digestive" processes for plants, but not for mammals. Finally, the question of whether early understanding of digestion can be termed "theory-like" was discussed.