Inverse reference in adults-elementary arithmetic.

Mauro, LeFevre, and Morris (2003) and Campbell (2008) manipulated problem format to assess university students' simple division and subtraction. Large division problems (dividend > 25; e.g., 42 / 6 = _) and large subtraction problems (minuend > 10; e.g., 13 - 6 = _), but not small problems, were solved more quickly when presented in inverse operation format (e.g., 6 x _ = 42 for division; 6 + _ = 13 for subtraction). They concluded that adults often solve large simple division and subtraction problems by reference to the inverse operation but rely on direct memory retrieval for smaller problems. Their findings, however, might have resulted from unequal practice or mixing of the inverse operations. Here, in Experiment 1 (division) and Experiment 2 (subtraction) normal and inverse formats received equal practice and only one operation was practiced (i.e., division or subtraction). Large divisions and subtractions were solved substantially faster when presented in inverse format, but there was also evidence that subtraction ties (e.g., 12 - 6 = 6) and small subtractions (minuend <or=10) benefited from inverse format. The results affirm that inverse reference is an important element in adult's performance of elementary subtraction and division.