Reading activity is taken as an example to show that the region of search for immediate information may encompass millions of mnemonic units. A question is thus provoked - how does the mind cope with the problem of finding the needed unit? A model is suggested, assumed to be sufficient to provide an answer, which is based on successive scanning in hierarchically organized memory. In order to prove the point successive scanning in the absence of such hierarchical organization is compared with it under conditions of available hierarchy. The results show that in complicated cases hierarchical memory facilitates the search hundred thousand times. A corresponding method of establishing the reaction time for any number of items is presented. Examples of realization of the method on the stimulus alphabet up to 23-106 are provided.