Research into reading, the promotion of reading and literature education

Free-time reading

-> Anyone who reads often becomes more proficient in reading and will consequently read more often. This upward spiral of causality applies to reading during free time, but also to ‘free-reading’ programmes at schools and ‘summer-reading’ programmes during holidays.

-> Performance at school benefits from improved reading proficiency. One's vocabulary improves due to the fact that more words are read and also because written texts contain many special words.

Reading in one’s free time

Reading behaviour and reading proficiency are part of a upward spiral of causality. People who often read fiction experience an improvement in their reading proficiency. Consequently, they become more self-assured about their reading competencies and, in turn, read more often in their free time. This results in an improvement in both text comprehension and vocabulary. In this way, reading behaviour and reading proficiency reinforce each other (Mol, 2010).

Upward spiral of causality

A meta-analysis of 99 international studies provides support for this upward spiral of causality. The effect of reading in one’s free time increases with each year of education and age. For instance, reading books explains 12% of the variance in oral language skills (vocabulary) of preschool children and toddlers, 13% of primary schoolchildren in the middle school classes, 19% of primary schoolchildren in the upper classes and secondary school children in the lower classes, 30% of secondary school children in the higher classes and 34% of students at universities of applied sciences and traditional universities. A smaller increasing effect occurs in relation to reading comprehension, while the percentages for technical reading skills (spelling, technical reading) remain almost the same—the upward spiral of causality therefore applies mainly to vocabulary and reading comprehension (Mol, 2010).

Effect sizes for reading comprehension components for preschool children and toddlers (in %)

Effect sizes for reading comprehension components for primary school children and secondary school children (in %)

Effect sizes for reading comprehension components for higher education students (in %)

In the case of poor readers, the result may also be a downward spiral. Infrequent readers have fewer opportunities to develop their reading proficiency. Consequently, they run the risk of experiencing problems with reading and will read even less. Mol (2010) warns of the Matthew effect: the achievement gap between passionate and hesitant readers as well as between proficient and poor readers will even widen during their lives.

At the same time, poor readers, in particular, may benefit from reading in their free time. In doing so, they are at an advantage relative to poor readers that do not read books at all. In addition, their basic reading skills (knowledge of the alphabet and phonological awareness) improve more strongly than those of proficient readers due to the fact that they ‘read in their free time’ (Mol, 2010).

Reading in one’s free time not only results in better reading proficiency, but also in better performance at school. Pupils in the final year of primary school who regularly read a book achieve higher scores for the language component of the national final primary school assessment (Cito test). This, in turn, results in their also achieving better outcomes in the Cito test for mathematics, study skills and world studies. The positive effect of reading in one’s free time is greatest in the case of high-level books (measured as the age indication on books). The use of other media, such as surfing the Internet, watching television and gaming correlates negatively to the scores for the Cito test (Kortlever & Lemmens, 2012).

Free reading at school

The upward spiral of causality between reading behaviour and reading proficiency not only applies to free time. Children who ‘read freely’ at school—from a book of their own choice, and without assignments or book reports—score as well as or even better for reading comprehension than children who did not do so at school. This conclusion is supported by 51 of the 54 studies in a meta-analysis. The effect is stronger the more free reading occurs during a longer period: programmes of a year or longer without exception result in even higher scores for reading comprehension. Free reading also promotes other aspects of reading proficiency, such as vocabulary, grammar and writing proficiency (Krashen, 2004). In addition, pupils who read freely at school derive more pleasure from reading (Chua, 2008).

Effect of free reading at school on reading proficiency

In number of studies

Free-time reading during the holidays

Free reading at school does not take place during the summer holidays. This appears to be disadvantageous mainly to children from families with a lower socio-economic background. They are generally stimulated less at home to undertake intellectual activities such as reading books. Consequently, during the holiday they develop their reading proficiency less strongly and the reading achievement gap between them and their classmates grows (CPB, 2016; Cooper et al., 1996).

Stimulating summer reading may prevent pupils from lagging behind. Children (in the United States) who are allowed to choose a package of books at the start of the summer holiday read more during the holiday. This has a positive effect on the reading proficiency scores after the summer (Kim, 2004; Kim, 2006). A meta-analysis of 41 studies shows that the effect on reading proficiency, expressed in Cohen’s d (<20), is 'very small' (Kim & Quinn, 2013). 

Summer reading programmes are effective, in particular, in the case of less skilled readers; children who have fewer books at home and children from poorer families (Kim, 2006; Allington et al., 2010; Kim & Quinn, 2013). Pupils from both primary schools and secondary schools benefit from these programmes (CPB, 2016).

Summer reading programmes are ideally accompanied by reading support provided by the teacher (prior to the holiday) and by the parents (during the holiday) (Kim & Quinn, 2013). Parents who receive text messages about summer reading on a weekly basis appear to stimulate their children to do so more (Kraft & Monti-Nussbaum, 2017). If the reading takes place at a summer school, the gains in reading proficiency will be greater (Borman & Dowling, 2006).

Why does vocabulary increase?

If pupils spend more time on ‘free’ reading at home and at school, they will read more words. Reading for an hour a day means reading 4 million words a year. This is 40 times as much as reading for a minute a day. Reading a greater number of words considerably increases the likelihood of extending one’s vocabulary (Cunningham & Stanovich, 2001).

Relationship between reading duration and volume

In number of minutes a day (horizontal axis) and number of words read per year (vertical axis)

There is a further reason why vocabulary benefits from ‘free’ reading. Written material contains a wide variety of so-called ‘low-frequency’ words. These are words which hardly occur at all on television and in day-to-day conversation, but do occur frequently in written texts. A children’s book even contains more low-frequency words than a random television programme or daily conversation (even between adults). Such words even occur in greater numbers in comic strips, newspapers, magazines and books, fiction and non-fiction, for adults (Cunningham & Stanovich, 2001).

Relationship between language genre and the number of special words

In number of words


Leesmonitor (2021). Free-time reading.
Reading Monitor (2021). Free-time reading.