How do people identify fragmented letters? The identification of fragmented letters is one piece of evidence that the various elements of cognitive functions work well. This ability included in the cognitive functions is considered to be in common with the ability of human ancestry to distinguish animals camouflaged in jungles. This book is concerned with a new method for examining cognitive functions with the use of a computer system presenting fragmented letters of the English alphabet. The results of the test on the identification of fragmented letters have shown that there is neither gender nor age difference in correct answer rates on fragmented letters at several fragmentation rates. The findings indicate that the ability of healthy people to read the fragmented letter as well as the full letter is unaffected by the differences in age and educational history. The book also presents the mechanism of the vision system for identification of fragmented letters.