Operationalising duval’s geometrical figure apprehensionAntunović, Branka (Avtor) Manfreda Kolar, Vida (Avtor) assessment instrumentDuval’s frameworkgeometrical figure apprehensiongeometric reasoninggeometry teacher professional developmentUnderstanding geometric figures requires the coordination of visualisation, construction, and reasoning processes. While Duval’s framework of geometrical figure apprehension (GFA) has been widely discussed, limited research has examined how it can be operationalised in teacher professional development and systematically assessed in students’ learning. This study investigates the effects of a teacher professional development programme grounded in Duval’s GFA and introduces a newly developed assessment instrument designed to measure students’ coordination of apprehension types. A quasi-experimental design was employed with 88 seventh-grade students and four teachers from Croatian primary schools. Data were collected through pre- and post-testing using an eight-task instrument and analysed with non-parametric statistical methods. Results show statistically significant improvements in the experimental group compared to the control group, particularly in the overall coordination of perceptual, sequential, discursive, and operative apprehensions. The findings indicate that structured teacher support and targeted task design positively influence students’ geometric reasoning. The study contributes by demonstrating how Duval’s theoretical framework can be operationalised in classroom practice and by providing a validated instrument for assessing geometrical figure apprehension in school geometry.20262026-05-04 08:23:46Članek v reviji182212UDK: 373.32.016:51ISSN pri članku: 2165-8714DOI: 10.12973/eu-jer.15.3.871COBISS_ID: 276562435sl