HYPOTHESIZING THAT CONGENITALLY BLIND ADULTS WOULD SCORE LOWER ON TESTS OF ABSTRACTION THAN ADVENTITIOUSLY BLIND OR SIGHTED ADULTS, THIS STUDY TESTED 25 CONGENITALLY BLIND, 25 ADVENTITIOUSLY BLIND, AND 25 SIGHTED SUBJECTS. THE WECHSLER ADULT INTELLIGENCE SCALE (WAIS) VOCABULARY TEST WAS ADMINISTERED TO EACH GROUP AND RESULTS SHOWED NO SIGNIFICANT DIFFERENCE IN INTELLECTUAL LEVEL AMONG THE GROUPS. SUBJECTS WERE TESTED BY THE WAIS SIMILARITIES TEST, THE PROVERBS TEST, THE KAHN TEST OF SYMBOL ARRANGEMENT, AND THE NUMBER SERIES COMPLETION TEST. MEAN SCORES FOR THE CONGENITALLY BLIND WERE THE LOWEST OF THE THREE GROUPS IN THREE OF THE FOUR TESTS OF ABSTRACTION, THEREBY SUPPORTING THE HYPOTHESIS. ON THE NUMBER SERIES COMPLETION TEST, THE ADVENTITIOUSLY BLIND GROUP SCORED SIGNIFICANTLY BELOW THE SIGHTED GROUP, PERHAPS BECAUSE OF THE IMPORTANCE OF VISUAL IMAGERY ON THIS TEST. RESULTS REVEALED THE AGE OF ONSET OF BLINDNESS AS AN IMPORTANT FACTOR IN THE INTERPRETATION OF TEST SCORES. INCLUDED IS A 79-ITEM BIBLIOGRAPHY. THIS DOCUMENT IS ALSO AVAILABLE FROM THE AMERICAN FOUNDATION FOR THE BLIND, 15 WEST 16TH STREET, NEW YORK 11, NEW YORK, FOR $0.90. (DF)