Task I A circuit was setup on a table and the teams were challenged to draw its diagram (Fig. 1). All drafts were drawn on the task worksheet. There was a special place for the final diagram. Students marked their degree of confidence in the correctness of their solution on a four-grade scale: (1) not sure at all (2) not so sure (3) almost sure (4) completely sure. The time of completion was marked on the worksheet. Task I required the ability to analyse the way in which several components are connected by wires and to translate the topology to a formal representation. Exploring the function of the circuit was especially difficult because: • One of the two switches was connected in an unusual way (parallel to a bulb). • There are four possible combinations of the states of the switches. A very careful exploration process is required to follow all cases. • Opening and closing the switches affected the bulbs’ brightness. This information was not necessary for solving the problem, but it attracted students’ attention and may have prevented them from focusing on the main effect. Three types of solutions were defined: • Correct solution: diagrams representing the exact topology of all components. • Partial solution: diagrams that included the parallel switch and could account for the function of three out of the four possible combinations of the switches’ states. • Incorrect solutions: all the rest, including shorts across components, only serial switches and ‘illegal’ diagrams.