ABSTRACT
Difficulties associated with demonstrating fundamental learning processes to large groups of students without large costs have inspired many ingenious laboratory exercises requiring simple equipment. One successful approach uses planarians (e.g., Dugesia dorotocephala) as experimental subjects. As Katz (1978) noted, planarians occupy a unique position in evolutionary history as the earliest bilaterally symmetric animals. These simple, aquatic, invertebrate flatworms evince synaptic nerve conduction and are capable of learning. Planarians are small (1 to 2 cm long), nonthreatening to students, inexpensive, and easy to care for (see Kenk, 1967). Descriptions of planarian anatomy (e.g. Pearse, Pearse, Buchsbaum, & Buchsbaum, 1987; Stachowitsch, 1992) and behavioral biology (e.g., Jenkins, 1967) are readily available. These animals exhibit habituation classical conditioning, and instrumental conditioning (reviewed by Coming & Kelly. 1973). Descriptions of planarian based laboratory exercises for educational settings are available for classical and instrumental conditioning (e.g., Abramson, 1990; Katz, 1978) but not for habituation and sensitization. The latter phenomena can be shown using other invertebrates (e.g., Abramson, 1990), but the specialized equipment required may make such exercises impracticable with large groups of students.
