This study aims to investigate about the existence of a graphical facilitation effect on probabilistic reasoning. Measures of undergraduates' performances on problems presented in both verbal-numerical and graphical-pictorial formats have been related to visuo-spatial and numerical prerequisites, to statistical anxiety, to attitudes towards statistics and to the confidence in response correctness. Psychology undergraduates in Italy and Spain with no statistical expertise (N= 676) completed a protocol under conditions of presence versus absence of time pressure. Hierarchical linear regressions and ANCOVAs with mixed design have been carried out separately for each sample. The best predictor of performance in both formats has been the confidence in solution correctness under the condition of time pressure administration, which seemed to promote the commitment to the task. The findings suggest that the eventual occurrence of a graphical facilitation could be the result of a multifactorial interaction among contextual and individual dimensions, rather than being strictly related to the problem presentation format.