We next examined the effects of increasing interference, that is, increasing block length from 60 items to 180 items in older adults and from 180 to 300 items in younger adults (see Figure 3, right; raw scores in Table 3). To do so, we submitted participants’ d′ scores to a 2 × 2 × 2 mixed ANOVA with Block Length (short, long) and Test Format as within-subject factors and Age as a between-subjects factor. The ANOVA revealed significant main effects of Block Length, F(1, 77) = 18.80, p < .001, ηp2 = 0.1960, Test Format, F(1, 77) = 42.77, p < .001, ηp2 = 0.357, and a marginal effect of Age, F(1, 77) = 3.48, p = .066, ηp2 = 0.043. These main effects were qualified by a significant Block Length × Test Format interaction, F(1, 77) = 8.49, p < .005, ηp2 = 0.099, and Test Format × Age interaction, F(1, 77) = 5.38, p < .05, ηp2 = 0.065. To investigate how the effects of Block Length and Age varied across Test Format, we conducted follow-up Block Length × Age ANOVAs separately for Forced Choice and Yes/No Test performance.