By means of action's interruption method the peculiarities of cognition and memory interrelation on operational level were studied. It was established that cognitive operations notable for content analysis and mnemonic ones characterized by material form analysis, constantly superseded each other. Both these actions included the features of another but in obliterated form. Ziegarnik's effect properties on different stages of interruption of cognitive and mnemonic operations were exposed. The process of these actions implementation was studied and its components shown: productivity, content treatment of material quality, analysis and transformation of its external form.