Children’s Eye Movements during Reading (стр. 3 )

Given their differences in age groupings of participants and the manner in which certain measures are reported (e. g., the number of regressions being reported either as the number made per sentence or as a percentage of all movements made), it is not possible to make meaningful comparisons between the magnitude of effects observed in studies that have used the same stimuli for readers of all ages and the magnitude of effects observed in studies that have used different stimuli for each age group. Importantly, though, all studies show the same basic developmental trends – it does not seem to be the case that the selection of more or less difficult materials for any given age group will differentially reflect age-related changes in eye movement behaviour to a substantive degree. Further, the results of these studies broadly agree that developmental changes in eye movement behaviour reach adult levels around the age of 11-years (see Table 1).

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One interesting point to note is that, in studies where different sentences were written for each age group in order to try and control processing difficulty, age-related changes in eye movement behaviour may be a consequence of age-related changes in identification of the individual words in the sentences. Specifically, these differences in eye movement behaviour may reflect slower or less efficient lexical identification in children compared to adults, despite the sentences being age-appropriate. This suggestion is supported by more recent data showing that linguistic skills (word/ picture naming speed) but not oculomotor skills (saccade latency on pro - and anti-saccade tasks) at the age of 8 predict sentence reading times at the age of 10 (Huestegge et al., 2009). To be clear, these data indicate that a child’s lexical processing ability can predict some aspects of their eye movement behaviour across sentences as wholes. The most important point to note, however, is that basic developmental changes in eye movement behaviour when reading sentences (as shown in Table 1) have been observed very consistently in all the studies published to date.

4. Saccadic targeting to words

An important aspect of eye movement behaviour during reading is where a reader locates their initial fixation (or subsequent refixation) on a word, and the consequences that landing positions on words have for ongoing language processing. This is important because we know that in adult readers, initial fixation location influences how quickly a word is processed (Vitu, McConkie, Kerr, & O'Regan, 2001), and also how likely it is that the word will be refixated (McConkie, Kerr, Reddix, & Zola, 1988; McConkie, Kerr, Reddix, Zola, & Jacobs, 1989). Three studies have examined landing position effects in children during normal text reading (Joseph et al., 2009; McConkie et al., 1991; Vitu et al., 2001).

McConkie et al. (1991) reported data from Grimes (1989), which showed that during their first year of reading instruction, children exhibited the same pattern of landing positions as adults, although full analyses were not reported. Furthermore, McConkie et al. found that, like adults, children were more likely to refixate a (five-letter) word following an initial fixation on the space before the word or on the first letter, than if the first fixation was close to the word centre (although these inferences were made from observing trends in the data rather than from conducting formal statistical analyses).

Vitu et al. (2001) conducted extensive analyses on three data sets, one of which used data from children who were approximately 12-years-old. Although the aim of the study was not to compare children and adults, the data from the Vitu et al. study showed that children did not appear to differ from adults in the locations of their first or second fixations. Like adults, children targeted their saccades towards the word centre and landing position distributions shifted with word length (that is, the longer the word, the further into the word children’s fixations were located). Also, like adults, and similar to the data reported by McConkie et al., children were more likely to refixate a word following an initial fixation away from the word centre (i. e., at the beginning or end of a word) than following a fixation close to the word centre.

Finally, Joseph et al. (2009) used tightly controlled experimental materials to make direct comparisons of landing positions between adults and children aged 7- to 11-years, as they read sentences containing target words which were four, six or eight letters long. They found no reliable differences in the location of initial fixations between adults and children for any word length. They also found, in line with previous studies, that both adults and children were more likely to refixate a word following an initial fixation away from the word centre. In addition, they found that children’s refixation saccades were smaller than those of adults, and tended to be regressive more often than adults’, although this trend was not significant.

Taken together, the data from these three studies show that very early in reading development (as young as 7-years), children target their saccades towards the word centre (McConkie et al., 1991; Vitu et al., 2001), and they do not differ reliably from adults in their initial landing positions (Joseph et al., 2009). Furthermore, children (like adults) are more likely to refixate a word following an initial fixation away from the word centre (that is at the beginning or end of a word) than following a fixation close to the word centre (Joseph et al., 2009; McConkie et al., 1991; Vitu et al., 2001), presumably because their initial fixation location does not allow them to extract the visual information necessary to complete lexical identification of the word. However, children appear to be less efficient than adults in targeting their refixation saccades (Joseph et al., 2009).

It seems, then, that although children are limited in the amount of parafoveal information available to them during reading compared to adults (i. e., they have smaller perceptual spans: see Section 5.1 below), the parafoveal information that is available to them during normal text reading is used effectively to guide their oculomotor behaviour in order to maximise reading efficiency (although they appear to lag behind adult efficiency when more than one fixation on a word is required). It is worth noting that some aspects of eye movement behaviour during reading may arise due to basic oculomotor phenomena, independent of learning to read. While reading development might be linked to deciding which word to fixate, the actual saccade targeting and preview mechanisms may simply be a basic characteristic of the eye movement control; for example, the finding that both adults and children both tend to target saccades to the middle of words may be characterised as a global effect (Findlay, 1982), a phenomenon not necessarily associated with reading. Nevertheless, research to date shows that children target their saccades to word centres, and this ability develops either before reading instruction begins or else within the first year of reading instruction.

5. Extent and time course of information extraction during fixations in reading.

There have been several strands of research that have employed innovative methodologies to examine in detail how visual characteristics of text affect children’s ongoing language processing. This section reviews studies that have used the moving window technique, the boundary paradigm, and the disappearing text paradigm in order to investigate changes in both the spatial extent and the time course of information extraction during fixations with respect to development. We will consider each of these lines of research in turn.

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5.1. Spatial limitations on information extraction.

Two studies have examined developmental changes in the perceptual span, the area of text around the point of fixation from which useful information can be extracted (Häikiö et al., 2009; Rayner, 1986). Each of these will be discussed in turn, in some detail, as the ability to pre-process information from words to the right of fixation is a hallmark component of skilled adult reading, and being deprived of the opportunity to pre-process information from the right of fixation is extremely detrimental to adults’ reading (Rayner, 1975; Rayner, Inhoff, Morrison, Slowiaczek, & Bertera, 1981; Rayner, Liversedge, & White, 2006; Rayner, McConkie, & Zola, 1980; Rayner, Well, Pollatsek, & Bertera, 1982).

The perceptual span has been measured using the moving window paradigm, in which there is an area of text around the point of fixation which is presented normally, and this window of text moves with the eyes as the reader progresses through the sentence (McConkie & Rayner, 1975). Outside the window, the text is mutilated in some way – typically replacing the letters with xs, or other, visually-similar letters. The size of the window of unmutilated text that is available to the reader is manipulated, and reading behaviour for different window sizes is compared to reading behaviour for text which is presented normally in its entirety. Small windows typically reduce reading speed, as the reader is unable to pre-process information outside the window. The window size at which reading speed becomes equal to that for normal text shows the perceptual span. As the reader can read at their full speed with a window of a particular size, it is inferred that they do not make use of information further from the point of fixation than is available to them in that window. The perceptual span for adults is asymmetric about the point of fixation, extending from the beginning of the fixated word to around 14 or 15 characters to the right (see Rayner, 1998 for a summary).

In 1986, Rayner published a paper on the development of the perceptual span during reading. Four experiments were conducted that examined the size and asymmetry of the perceptual span in children of different ages compared to skilled adult readers, as well as the influence of text difficulty upon the perceptual span. The first experiment used windows that were symmetrical about the point of fixation; the perceptual span was shown to extend 23 characters around the point of fixation (11 characters to either side of fixation) for the two youngest groups of readers (7- and 9-years). In contrast, for 11-year-old children and the adults the perceptual span was larger, extending 29 characters around the point of fixation (or, 14 characters either side of fixation). When the window size was determined in terms of words rather than characters, and word spaces outside the window were preserved so that the reader had parafoveal access to upcoming word length information, both reading rate and eye movement data again showed that younger readers have a smaller perceptual span than older readers, with a span of one word to the right of fixation for 7-year-olds but a span of two words to the right of fixation for 9-year-olds, 11-year-olds, and parisons across word - and character-defined window conditions also showed that, consistent with previous adult studies, readers as young as 7-years-old pre-process word length information at a greater eccentricity from fixation than they pre-process letter-specific information.