Children’s Eye Movements during Reading (стр. 5 )

An interesting question that arose from the disappearing text studies was whether children are able to encode visual information during fixations in reading as quickly and efficiently as adults. Beginning readers are, by nature, less familiar with the written forms of words than skilled adult readers. It may, therefore, be the case that they require longer presentation durations than adults to allow successful visual encoding and, consequently, the initiation of normal linguistic processing. Blythe and colleagues compared younger children (7- to 9-years), older children (10- to 11-years) and adults as they read sentences presented as disappearing text (Blythe et al., 2009). The sentences contained a target word that was manipulated for word frequency. In two experiments, four different presentation durations were used – 40 ms, 60 ms, 80 ms, and 120 ms disappearing text compared to normally-presented sentences. The results showed that even by the age of 7-years, there was a minimal impact of the disappearing text manipulation upon children’s eye movement behaviour with all presentation durations tested. Effects of word frequency were found upon single and first fixation durations even in the disappearing text conditions, providing strong evidence that even with very short periods of visual input, children aged 7-years are able to initiate normal lexical identification processes. These results are comparable to those obtained for adults.

In summary, the data from studies which have investigated visual information extraction during reading shows that (1) the perceptual span for reading increases in size with chronological age, up to 11-years and is related to reading skill/ processing difficulty; (2) the characteristic left-right asymmetry of the perceptual span associated with skilled adult reading of English has developed by the age of 7-years; (3) by the age of 7-years, children accurately target their saccades close to the word centre, as adults do; and (4) the speed of visual information encoding during reading does not increase significantly after the age of 7-years. Thus, while spatial aspects of information encoding continue to develop up to 11-years, where a child initially fixates a word and the speed with which a word is visually encoded are in place just a few years after beginning formal reading instruction, or perhaps even before (see Section 4).

In the latter half of this review, we will consider how various characteristics of the material being read can impact upon the eye movements of children compared to adults. Studies in this area have used eye movements as an index of the moment-to-moment psychological processing that underlies reading, to examine the process of development from beginning to skilled reader.

6. Word-based effects in children

Two of the most robust effects in the adult eye movement literature are those of word length and word frequency; that is, adults look longer at long than short words (Just & Carpenter, 1980; Rayner, Sereno, & Raney, 1996); and at low frequency than high frequency words (e. g., Henderson & Ferreira, 1990; Inhoff, 1984; Inhoff & Rayner, 1986; Just & Carpenter, 1980; Rayner, 1977; Rayner & Duffy, 1986; Rayner et al., 2003; Rayner & Raney, 1996). Perhaps for this reason, the majority of studies which have manipulated an aspect of text to examine its effect on children’s eye movements during reading have focussed on precisely these two characteristics.

6.1. Word length.

Four studies have manipulated word length to investigate whether these robust effects (whereby long words are fixated more often and for longer than short words) observed in adult readers are also present in children. Hyönä and Olson (1995) recorded the eye movements of both dyslexic children (mean age = 14.4 years) and reading-age-matched controls (mean age = 10.5 years) as they read aloud texts which contained words that were, subsequent to data collection, categorised as short (5-6 letters), medium (7-8 letters), or long (9-11 letters), resulting in a very high number of target words and, hence, a very rich data set. The reading material was set at a higher difficulty level than most participants’ level of word recognition in order that some reading errors would be generated. Hyönä and Olson found a strong effect of word length in both groups which was apparent in gaze durations (the sum of all fixations made on a word before the eyes leave the word either to the right or to the left), number of first pass fixations (the number of fixations made on a word before leaving that word to the right or left), second pass reading time (the sum of all fixations made on a word after having left the word for at least one fixation); and number of second pass fixations (the sum of all fixations associated with second pass reading).

In a silent reading experiment, Joseph et al. (2009) took a different approach to that of Hyönä and Olson, and manipulated word length prior to data collection, which meant that they were able to control for word frequency and predictability in their target words (one per sentence). This allowed them to ensure that any effects observed were due to word length alone rather than being modulated other linguistic variables. Furthermore, the experimental sentences were designed to be age-appropriate for the youngest of the children (aged 7-years), which meant that they were relatively easy for the older children (aged 11-years) and adults.

Like Hyönä and Olson, they found reliably longer gaze durations, more refixations, and longer total reading times on long than short words. They also found that both adults and children skipped short words more often than long words. Importantly, most of these effects were larger in children than adult readers, suggesting that not only do children experience an increased processing load when reading long as compared to short words, but the increase in word length has a more substantial effect on children’s ongoing lexical processing as compared to that of adult readers. Furthermore, due to careful control of word frequency and predictability, it is likely that this difference between adults and children was due to the demands of visually encoding long as compared to short words, suggesting that children require more and/or longer visual samples of long words in order to reach the point at which lexical identification can proceed.

Similarly, Huestegge et al. (2009) found that children aged 8- and 10-years old exhibited longer gaze durations and total fixation times on long (6- to 9-letter) compared to short (4- to 5-letter) words and, like the previous two studies, did not observe an effect of word length on children’s first fixation durations. They also found an interaction between age group and word length on refixation time (gaze duration minus first fixation duration) showing that the word length effect was greater in younger compared to older children. These data from silent reading experiments suggest, therefore, that younger readers need additional processing time on long words compared to older readers, and that this need decreases with age.

A more recent experiment has directly investigated the question of why children make multiple fixations on long words (Blythe et al., 2010). Children aged 8- to 9-years, 10- to 11-years, and adults read sentences containing long (8-letter) or short (4-letter) words, that were presented either normally or as disappearing text (for an explanation of the disappearing text paradigm, see Section 5.2 of this chapter). The 8-9-year-old children made fewer refixations on long target words when they were presented under disappearing text conditions compared to normal conditions (resulting in shorter gaze durations). However, they subsequently made more regressions back to long words in the disappearing text condition, leading to no overall difference in total fixation times on those long words between the normal and disappearing text conditions. Thus, these younger children adopted an eye movement strategy by which they obtained a second visual sample on the long words without incurring any cost to overall processing time on this ch effects were reduced in the older children, and were minimal in the adults, indicating that while younger children do require a second visual sample on 8-letter words, by the age of 10-years one visual sample is usually sufficient.

Together, these studies provide compelling evidence that children (up to the age of around 9-years) are slower and less efficient at processing words, evidenced by their need for multiple and longer visual samples when reading long compared to short words; this applies in the domains of both silent and oral reading. Moreover, word length effects are found in text that is relatively difficult (Hyönä & Olson, 1995) or easy (Blythe et al., 2010; Joseph et al., 2009) for those children reading it, and the effects observed are more pronounced in younger readers compared to older readers (Huestegge et al., 2009).

6.2. Word frequency.

Of the relatively small number of studies that have investigated word-based effects in children, many have specifically manipulated word frequency (Blythe et al., 2006; Blythe et al., 2009; Huestegge et al., 2009; Hyönä & Olson, 1995). Word frequency refers to how often a word is encountered, as indexed by corpora such as CELEX (Baayan, Piepenbrock, & Gulikers, 1995) and Kučera and Francis (Kučera & Francis, 1967), which document how frequently a given word appears in a range of written texts. It is likely that this particular variable was chosen in all of the four studies because the word frequency effect is so robust in adult readers (e. g., Henderson & Ferreira, 1990; Inhoff, 1984; Just & Carpenter, 1980; Rayner & Duffy, 1986; Rayner & Raney, 1996). It was, therefore, important to establish whether children’s eye movements were influenced as immediately and reliably as those of adults by the frequency with which a word is encountered.