The data on the pie chart item were collected during
individual interviews on pairs of items from three of the six
graphical languages (on another occasion, students were
interviewed about three pairs of items from the other three
graphical languages). The students selected the multiple
choice response for each pair of items and were then
invited to explain their responses. Here, we report on the
data collected on the pie chart item (Fig. 3), which was one
of the two miscellaneous language items in the interview (the other item was not a pie chart and, hence, is not discussed
in this paper)