Abstract
1970's in Japan, there were some developmental studies on students' logical thinking abilities. From these studies I have following implications: 1 Objects of these studies were the conditional reasoning, Venn diagram, a logical relationship between two figures, the transitive law of a relation and conditional judgment. 2 From studies on the conditional reasoing, we can see that the 'modus ponens' reasoning and the contrapositive reasoning are both easy for any students, but the inverse reasoning and the converse reasoning are both difficult for even university students. 3 Works in psychology suggest that conditional reasoning abilities are different each other by the contents and the context of the reasoning, and conditional reasoning abilities are educationable. And I point out that mathmatics educators in Japan are more concerned with 'teaching mathematics' rather than 'education by mathematics', because they ignore the results of these studies for the independence of logical abilities from mathematical ones.
