It is important to note that the NRP did not include any studies lasting longer than one year. A more comprehensive review of the literature indicates that the positive impact of recreational reading increases over time.

Even applying the NRP's stricter criteria, SSR does very well, with readers doing as well or better than comparisons in 35 out of 36 comparisons. This suggests that the "violations" do not affect the central issue of whether encouraging recreational reading impacts literacy development. Even if one only allows studies that strictly meet the NRP's criteria, the result still favors recreational reading.

Misinterpreted Studies

In addition to excluding relevant studies, the NRP misinterpreted some of the studies that it did include. Carver and Liebert 's study¹¹ should not have been cited as evidence for or against recreational reading because the students were constrained with respect to what they could read. They were allowed to read books only at or below their level, and the choice of books was limited to 135 titles (the regular library stacks were off limits). There was heavy use of extrinsic motivators, students had to take multiple choice tests on the books they read, and reading time was heavily concentrated, with students reading in two hour blocks. Successful sustained silent reading programs allow access to any books readers want to read, do not use extrinsic motivators, do not make students accountable for what they read, provide a wide variety of books, and typically meet for a short time each day over a long period.¹²

The NRP claimed that the advantage shown by readers in Joanne Burley's study¹³ was "small." Students in sustained silent reading were clearly significantly better in reading comprehension than comparison students in three other conditions, but it was not possible to calculate measures of the size of the effect. It is not clear how the NRP concluded that the difference was small, especially considering the fact that the treatment lasted only six weeks and contained only 14 hours of reading. In a response to a commentary of mine, Shanahan claims that "the problem here was not with the statistics, but with the design of the study. Each of the four treatments was offered by a different teacher, and students were not randomly assigned to the groups. It is impossible to unambiguously attribute the treatment differences to the methods."¹⁴ This is not accurate: Student assignment was in fact random and the four teachers were randomly assigned to one of the four groups.¹⁵ In addition, the group that did SSR was superior to all three comparison groups, taught by three different teachers.

Not included in my summary of studies in Table 2 is a study that the NRP did include. Janet Langford and Elizabeth Allen¹⁶ used the Slossen Oral Reading Test, which consisted of reading words aloud, which may or may not involve genuine reading comprehension. The difference between the groups was highly significant and I calculated an effect size of 1.005, which is quite large. Nevertheless, in discussing this study, the NRP concluded that "the gains were so small as to be of questionable educational value."¹⁷

In Gary and Maryann Manning's study,¹⁸ students who engaged in SSR made better gains than a comparison group, but the difference was not statistically significant. SSR was significantly better than traditional instruction, however, when readers interacted with each other, that is, when they discussed their reading with each other and shared books. The NPR refers to this group's advantage as "slight,"¹⁹ but it is not clear how they arrived at this conclusion. I computed a respectable effect size of .57 for the difference between the peer-interaction group and the comparison group.

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