According to the journal written by Mary Carol Day, the first characteristic is the formal operational individual’s thought can be described as hypothetico-deductive in nature. The formal thinker is able to construct hypothesis to account for particular phenomena, deduce from these hypotheses by finding out if event do occur. Second, the formal thinker can combine systematically a set of elements to create all possible combinations. This ability conduces to use of the control-of-variables strategy. The third is the formal thinker’s ability to consider only the logical relations between statements while ignoring the concrete content. Besides that, The fourth characteristic is the formal operational child thinks about the real and the possible differently that does the concrete operational child, who starts with the real and works toward the possible. In addition, the formal operational child also can even draw logically appropriate conclusions from invalid premises.