Özet:

Geometry is an important part of the mathematics curriculum. In the late 1950s, Pierre van Hiele and Dina van Hiele-Geldof developed a theory of learning geometry. Theory helps determine students' geometric thinking levels, design appropriate instruction for their level, and students move to the next level. This study aims to examine the studies focusing on van Hiele geometric thinking levels by using the meta-synthesis method and to reveal what kind of trend there is in this subject in mathematics education, how the studies meet the need in terms of quantity and quality, and what kind of research is needed. In the research, a total of 83 publications, including 33 articles and 50 theses published between 2003 and 2020, were determined to be analyzed. When we looked at the research findings, it was seen that determining the effects of different learning environments on the levels of geometric thinking was conducted to determine the levels of geometric thinking. A significant part of the studies was in the subject areas of triangles, polygons and quadrilaterals, scanning work and experimental studies were focused on, it was generally conducted with 7th and 8th-grade students at secondary school level, questionnaires and tests were preferred as data collection tools, the research process was based on teaching practice in only 41 publications, and the geometric thinking levels of the students were below the expected level in a significant part. Finally, the research was completed by recommending to practitioners and researchers who would work on this subject.

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