Reading habit is considered as an important variable in reading research. However, researchers often use the term habit synonymously to behavioral frequency. Thereby, the concept of habit often forms the theoretical foundation, even if in a particular study labels such as reading activity, behavior or frequency are used. Thus, it might be promising to adapt the elaborated habit concept by Verplanken and Orbell (2003) to reading research. We aimed to introduce a broader unidimensional conception of habit to reading research involving behavioral frequency, automaticity and the expression of one’s identity. We adapted the Self-Report Habit Index (SRHI, Verplanken and Orbell, 2003) introducing the Self-Report Habit Index for Reading (SRHI-R). We aimed to provide an economic measure that is easy to administer and can be used in typical research designs in reading research such as longitudinal large-scale assessments. In this study, we assessed the psychometric properties of the SRHI-R and investigated some aspects of its validity. Finally, we tested for the incremental validity over and above reading frequency. We will first review the conception of habit presented by Verplanken and Orbell (2003) before, we describe its application to reading.

Verplanken and Aarts (1999) define habit as “learned sequences of acts that have become automatic responses to specific cues, and are functional in obtaining certain goals or end states” (p. 104). For a detailed discussion of the habit construct see Bernacer et al. (2015). Following Verplanken and Orbell (2003) habit is best described as a unidimensional construct, e.g., it can be used as a compound measure assessing reading habit, covering several aspects characterizing habitual behavior. First, the history of repetition is important because a certain behavior has to have been executed successfully and repeatedly in the past to form a habit. Second, the expression of one’s identity is relevant because habits not only form the behavioral repertoire but also “reflect a sense of identity or personal style” (p. 1317)—partly because habits are part of how we organize our everyday life. Finally, automaticity is an important component of habit comprising three aspects (Bargh, 1994): First, lack of awareness refers to a lack of a conscious intent or not being aware that a process is instigated. Second, mental efficiency suggests that habits free mental capacities and thus enable us to shift attention to additional processes. Third, lack of control means that habitual behavior is only controllable to a certain degree, which may be easily understood when thinking of how hard it can be to break a bad habit (Verplanken and Faes, 1999; Adriaanse et al., 2014; Güell and Núnez, 2014) or to develop new habits (Page and Page, 2014). It is important to note that habits develop by successful and satisfying repetition in stable contexts, whereby not only repetition but also automatization of the behavior is essential for the definition of habit (Verplanken et al., 2005).

Verplanken and Orbell (2003) developed the SRHI, a short measure of habit strength accounting for these aspects of habit. The SRHI showed excellent internal consistency; content, discriminant, and predictive validity were good for a variety of different behaviors such as health behavior, social chatting, transportation mode choices, and mental habits (Verplanken, 2006).

In reading research habit has mostly been measured as reading frequency, reading amount, or reading activity. Thereby, the particular label used is not always equivalent to the meaning of a construct. In fact, many researchers at least implicitly aim to assess reading habit. For example, the Reading Activity Inventory claims to also assess “reading habit” (p. 10, Guthrie et al., 1994) without defining this term at all. Our aim was to apply the aforementioned conceptualization of habit to reading providing a more elaborated theoretical framework for investigating reading habit.

There are several approaches claiming to measure reading habit. Questionnaires are frequently used but often consist of only one to a few items assessing reading frequency or directly asking about reading habit (e.g., Applegate and Applegate, 2004; OECD, 2010). Measures of behavioral frequency have been criticized as described above. Moreover, Verplanken et al. (2005) argue that once a habitual behavior is established, repetition is needed in order to sustain it as a habit. Asking for enjoyment might mix up reading motivation and habit to some extent. Moreover, it can be difficult to retrieve episodic memories if asked for behavioral frequency in the past (e.g., “How often/long did you read last week?”), or when the habit concept being questioned is not conceptualized clearly (Verplanken, 2010). Finally, one-item measures are “notoriously unreliable” (Verplanken, 2010, p. 72).

Other approaches used diary studies, reading log books, or task analyses to assess reading habit (Taylor et al., 1990; Allen et al., 1992). Diary methods or log books seem to be a promising approach measuring habit. However, these approaches also only consider reading frequency and they are quite time-consuming for participants and researchers, and can often not be implemented in research designs, such as longitudinal large-scale assessments (cf. Wigfield and Guthrie, 1997). Moreover, Verplanken (2006) argues that the diary method makes participants more aware of their behavior and thus—at least for social desirable behavior—may lead to an overestimation of behavioral frequency and in turn to an overestimation of the actual habit. Finally, diary methods as measures of reading frequency in general may lead to a misinterpretation for example when a child is asked to read daily by his or her parents.

There are manifold approaches for measuring whether individuals read often and broadly. However, these instruments are mostly restricted to behavioral frequency. Following Verplanken (2010) such instruments are not valid measures of habit since they “fail to measure any other aspect of habit than behavioral frequency” (p. 72).

The aim of our study was to introduce a broader habit conceptualization in reading research as well as to validate the SRHI-R as an efficient measure of reading habit. We adapted the SRHI (Verplanken and Orbell, 2003) to reading. Following Verplanken et al. (2005), we only adapted ten out of twelve items, since for some behaviors single items of the SRHI may be less useful for measuring the according habit.

First of all, we tested the dimensionality of the SHRI-R. Habit in its essence is understood as a unidimensional psychological construct even though it comprises aspects of the history of repetition, automatization, and identity. Thus, we expected a unidimensional factor structure for the SRHI-R that has been empirically supported for the original SRHI (Verplanken and Orbell, 2003; Verplanken et al., 2005). Second, we tested psychometric properties (reliability, item difficulties, item selectivity) before, we investigated some aspects of validity—measurement invariance, correlations with external criteria, and incremental validity compared to behavioral frequency.

Regarding measurement invariance, we focused on gender and students in different thematic study-profiles as relevant subpopulations. Thematic study-profiles, namely esthetics, language, science, social science, or sports represent the main field of study in upper secondary schools in some federal states of Germany.

We considered five theoretically derived external criteria for which, we expected the following correlations. First, we expected high positive correlations between the SRHI-R and traditional measures of reading frequency. Second, we expected positive correlations between the SRHI-R and intrinsic reading motivation and reading self-concept as important aspects of reading motivation (cf. Retelsdorf et al., 2011). Third, we expected differential correlations between the SRHI-R and the proximal verbal self-concept versus the distal mathematics self-concept as a test of convergent and discriminant validity. Fourth, in a similar vein, we expected differential correlations with school grades in the first language (German) and mathematics. Fifth, we expected positive correlations with reading achievement and decoding speed since reading habit should lead to a higher extent of reading practice and, thus, to an enhancement of reading (Mol and Bus, 2011). Finally, we tested if the SRHI-R explains additional variance in reading achievement and decoding speed over and above measures of behavioral frequency.

Reading habit plays an important role in reading research (e.g., Wang and Guthrie, 2004; Schiefele et al., 2012). Although many studies deal with this topic or related research questions, the theoretical fundamentals of reading habit have seldom been discussed. Researchers mostly use simple measures of behavioral frequency to capture habit. Following discussions (Verplanken and Orbell, 2003) on how to understand and measure habit in general (i.e., not particularly in the reading domain), we aimed to introduce the idea that habit is more than just behavioral frequency to reading research. Therefore, we adapted the well-established SRHI (Verplanken and Orbell, 2003) to reading research.

As was well supported for the original measure (Verplanken et al., 2005) the SRHI-R turned out to be unidimensional. Even though, small modifications were necessary to obtain a good model fit for the unidimensional CFA, the empirical evidence for this model seems reasonable. First, the results of the EFA clearly indicated a single factor solution with nearly 80% of the variance explained by the first factor. Second, when evaluating the model fit of the non-modified unidimensional CFA, the RMSEA is the only index suggesting a bad model fit, while CFI, TLI, and SRMR meet the cut-off criteria given as thumb rules in the literature. Third, theoretically habit is understood as a unidimensional psychological construct comprising broad content. Thus, we feel that the small hints on possible multidimensionality of reading habit in our study should not be overrated. At least, we are convinced that it is feasible to assume essential unidimensionality for the SRHI-R (see e.g., Slocum-Gori et al., 2009 for a discussion of essential dimensionality).

The SRHI-R showed good psychometric properties. Moreover, the invariance of the measurement model was supported for two sets of subpopulations (gender and thematic study-profiles), indicating that it was valid for these groups. In order to obtain indicators of external validity, we investigated correlations with a set of external criteria. As expected, reading frequency and the SRHI-R correlated strongly. Due to the high correlation, we investigated the predictive power of the SRHI-R compared to reading frequency. As expected, reading habit was correlated positively with achievement outcomes, namely reading achievement and decoding speed. For both, the SRHI-R turned out to be a better predictor. When also including intrinsic reading motivation as a predictor the findings become somewhat more differentiated. Predicting reading achievement, the effect of the SRHI-R vanishes indicating that the habit effect may be explained by higher motivation. However, predicting decoding speed, the effect of SRHI-R remained significant when including intrinsic reading motivation. These differential relations of habit and motivation with different aspects of reading cannot be explained in detail with the current study. However, it seems plausible that for different aspects of reading different determinants are important, since we know from previous research that different reading skills vary in their development (e.g., Bast and Reitsma, 1998; Aunola et al., 2002; Retelsdorf et al., 2012). Thereby, habits may be more important for rather basic reading skills such as decoding speed than for more complex reading skills as measured by our reading achievement test. For such basic skills high amounts of reading practice may be particularly relevant since they benefit from high levels of automatization (cf. Stanovich, 1986). Such high amounts of practice as well as automatization are essentials of reading habit as, we understand it. Despite the different results for reading achievement and decoding speed, these findings highlight the fact that the scale could make a contribution to the research on prerequisites of reading outcomes. Moreover, given the differential unique contributions of motivation and habit to decoding speed, we think that both variables indeed measure unique constructs.

Finally, the differential correlations with school grades in German as the first language and mathematics as well as verbal and mathematics self-concepts corroborated our assumptions. All in all, the correlations and group comparisons yielded the expected results supporting the validity of the SRHI-R. As an economic measure, we hold the SRHI-R to be a useful measure even for longitudinal large-scale assessments.

Next to these hints toward sufficient quality criteria of the SRHI-R, we again want to stress two advantages compared to typical measures of reading habit. First, the reliability can be expected to be higher in comparison to the typical one- or two-item measures. Second, and most importantly, the SRHI-R is embedded in a theoretical framework of habit so that it may reflect a more elaborated understanding of habit. This deeper understanding of reading habit may also stimulate new research regarding antecedents and consequences of reading habit.

Both authors did contribute substantially to the conception and design of the work. JR was predominantly responsible for the acquisition of the data. FS did the majority of the analyses and interpretation of the data. FS drafted the work and JR revised it critically for important intellectual content. Both authors give final approval of the version to be published and agree to be accountable for all aspects of the work and ensure that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.