How Good Are Students at Testing Alternative Explanations of Unseen Entities?

THE purpose of the present study is to test the hypothesis that a fifth stage of intellectual development characterized by the ability to test alternative explanations involving unseen theoretical entities exists. This fifth-stage hypothesis will be tested in the context of a nonmajors, college-level biology course in which the assumption is made that some, but by no means all, students have acquired stage-five reasoning skills. Jean Piaget’s well-known developmental theory proposes that the development of thinking skills, which most would characterize as ‘‘scientific,’’ takes place in a stage-like fashion. Stage one, the sensorymotor stage, lasts from birth to about 18 months. As the name suggests, the stage involves the development of sensory-motor knowledge and acquisition of practical knowledge such as the fact that objects continue to exist even when out of sight. Stage two, the pre-operational stage, lasts until seven years of age. This stage primarily involves development of the ability to speak and understand the spoken word. Stage three, concrete operations, which begins at age seven, involves the development of descriptive thinking skills in which the child acquires an understanding of class subclass relationships and begins to understand the world in terms of specific variables such as weight, length, area and volume (e.g. Flavell 1963; Inhelder & Piaget 1958; Lawson & Renner 1975; Piaget & Inhelder 1969; Trifone 1991). Potential for moving into Piaget’s fourth and highest stage of thinking, called formal operational, generally occurs between 11 and 12 years of age. Inhelder and Piaget (1958) invented several widely used tasks to find out whether or not students have developed formal thinking patterns. A prototype task is the pendulum task. The pendulum task asks students to identify variables that may cause differences in the rate at which pendulums swing. If a student conducts controlled experiments to test the possible effects of