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Abstract In this paper, we apply the basic idea of a trade-off between the level of concentration and distractibility to test whether a manipulation of task difficulty can shield against distraction. Participants read, either in quiet or with a speech noise background, texts that were displayed either in an easy-to-read or a hard-to-read font. Background speech impaired prose recall, but only when the text was displayed in the easy-to-read font. Most importantly, recall was better in the background speech condition for hard-to-read than for easy-to-read texts. Moreover, individual differences in working memory capacity were related to the magnitude of disruption, but only in the easy-to-read condition. Making a task more difficult can sometimes facilitate selective attention in noisy work environments by promoting focal-task engagement.

2. Results 2.1. Task difficulty ratings and reading speed The task was perceived as more difficult (M = 2.63 vs. M = 4.88, t(31) = 7.31, p < .001) and more demanding (M = 2.41 vs. M = 5.28, t(31) = 8.35, p < .001) when the text was displayed in the hard-to-read compared with the easy-to-read font. This corroborates the effectiveness of the font manipulation in making the task more difficult. Reading took somewhat longer with the hard-to-read font but this difference was not significant (M = 53.31 s vs. M = 51.92 s, t(31) = 0.93, p = .359). One interpretation of these results is that the participants compensated for the greater demand on reading by concentrating harder and thus engaging more with the task. 2.2. Memory for written prose As can be seen in Fig. 1, this greater need for concentration benefited prose memory. The background speech impaired memory when the text was easy-to-read but not when the text was hard-to-read. Most importantly, recall was better for texts read in a hard-to-read font against a speech noise background than for texts read in an easy-to-read font in the same background condition. This conclusion was supported by a 2(task difficulty: easy-to-read vs. hard-to-read font) × 2(background condition: Silence vs. background speech) analysis of variance that revealed no significant main effect of task difficulty, F(1, 31) = 0.12, p = .729, View the MathML sourceηp2=.004, and no significant main effect of background condition, F(1, 31) = 1.39, p = .234, View the MathML sourceηp2=.04, but a significant interaction between the two factors, F(1, 31) = 31.01, p = .004, View the MathML sourceηp2=.23. Simple main effects analysis (with LSD adjustment) showed that recall was impaired by background speech in the easy-to-read condition, p = .002, d = 0.48, but not in the hard-to-read condition, p = .398, d = 0.16. Furthermore, recall was better in the presence of background speech when the text was hard-to-read compared to when text was easy-to-read, p = .032, d = 0.37. Mean number of the percentage of correct answers on a test of memory for prose ... Fig. 1. Mean number of the percentage of correct answers on a test of memory for prose displayed in two task difficulty conditions (easy-to-read and hard-to-read texts) and read in two background conditions (silence and background speech noise). Figure options 2.3. Relation between working memory capacity and distractibility To analyze the relationship between working memory capacity and distractibility in the two task difficulty conditions, we used the difference scores (i.e., subtracting the memory score in the silent condition with the memory score in the background speech condition) for both task difficulty conditions, respectively, and correlated these difference scores with the SICSPAN scores. The silence and background speech variables had an internal consistency of α = .80 (silence, SD = 0.16; background speech, SD = 0.15) in the easy-to-read condition, and α = .65 (silence, SD = 0.17; background speech, SD = 0.16) in the hard-to-read condition. As shown in Fig. 2, higher SICSPAN scores were associated with a smaller distraction magnitude when the text was displayed in an easy-to-read font, r(30) = −.35, p = .050, 95% CI [−.62, −.002], but no such relationship was found when the text was displayed in a hard-to-read font, r(30) = −.05, p = .779, 95% CI [−.39, .30]. However, the difference between the two r-values ( Meng, Rosenthal, & Rubin, 1992) was not statistically significant, z = −1.01, p = .312. The figure shows the relationship between individual differences in working ... Fig. 2. The figure shows the relationship between individual differences in working memory capacity (i.e., size-comparison span scores) and the magnitude of the effects of background speech on prose recall (all z-values) in the easy-to-read condition (panel A) and in the hard-to-read condition (panel B).