The aim of the current study was to identify the effect of the training program based on systemic thinking skills on the level of performance, and the level of perceived mental effort associated with performance when dealing with difficult and complex tasks. To this aim, a scale of perceived mental effort and a scale of perceived difficulty were prepared, in addition, a program based on the systemic thinking skills which were established by Richmond in 1993 was prepared. The program was applied to a sample of (48) from university's students .
By calculating the significance of the difference between the means of ranks on both performance and perceived mental effort before and after the application of the program using the Wilcoxon test for the related samples, it was found that there is a significant difference between the two means of ranks of performance in favor of the post-measurement, as the level of performance increased significantly after the application of the program. It was also showed that there was a significant difference between the two means of ranks of perceived mental effort obtained on the pre and post-measurements in favor of the pre- measurement, as the perceived mental effort level decreased significantly after the application of the program. The instructional efficiency of the intervention based on systemic thinking has been calculated. It had the value of E = 2.76, which is a positive efficiency, indicating high level of performance compared with the perceived mental effort after the application of the program.