Effects of multiplication practice on product verification: integrated structures model or retrieval-induced forgetting?

In the integrated structures model of simple multiplication (Manly & Spoehr, 1999), it is proposed that retrieval of a multiplication fact (e.g., 2 x 7 = ?) activates and strengthens operand multiples representations (e.g., 4, 6, 8, etc.; 14, 21, 28, etc.). In contrast, in the phenomenon of retrieval-induced forgetting (RIF; M. C. Anderson, Bjork, & Bjork, 1994), it is suggested that operand multiples ought to be suppressed with practice. Participants (N = 72) performed 40 blocks of practice trials in which they generated answers to a subset of simple multiplication problems. We then measured response times and errors in a true-false product verification task. Both true and related false equations with practiced operand multiples as presented products were solved relatively poorly in the verification task. In agreement with RIF, this suggests that operand multiples were suppressed, rather than strengthened, during the practice phase.