In this study we have investigated the relationship between the field-dependence-independence (FDI) dimension as measured by the Group Embedded Figures Test (GEFT) and subject performance on the Longeot test, a pencil-and-paper Piagetian test, through the open or closed format of its items. The sample consisted of 141 high school students. Correlation and variance analysis show that the FDI dimension and GEFT correlate significantly on only those items on the Longeot test that require formal reasoning. The effect of open- or closed-item format is found exclusively for formal items; only the open format discriminates significantly (at the 0.01 level) between the field-dependent and -independent subjects performing on this type of item. Some implications of these results for science education are discussed.