In an qualitative study of TI-89 use in a Precalculus class, the device played an important, mediating role in the progressive evolution of mathematical thought, from the concrete to the abstract, or from material to theoretical knowledge. This study provides a detailed account of how deep conceptual understanding can build through use of a graphing calculator.

This is a summary of the full paper:
Rivera, F.D. (2007), Accounting for Students Schemes in the Development of a Graphical Process for Solving Polynomial Inequalities in Instrumented Activity. Educational Studies in Mathematics. Downloaded from Online First, January, 2007.