Children’s Eye Movements during Reading (стр. 6 )

In the same study outlined in the previous section, Hyönä and Olson (1995) also investigated word frequency effects. Words of each length were categorised into three frequency groups: low, medium and high. They found a strong effect of word frequency in oral reading which could be seen in first fixation durations, showing that the frequency of a word has a very immediate effect on processing in children, as it is known to do in adults. Importantly, the word frequency counts of the target words were drawn from age-appropriate texts so that the high and low frequency words were high or low frequency for children, rather than for adults. While this study suggests that the frequency of occurrence of a word has an immediate effect on the reading behaviour of children as well as adults, a more recent study by Blythe et al. (2006) failed to find a frequency effect in children aged 7- to 11-years, despite finding a strong frequency effect in their adult participants in the same study Importantly, this study used adult corpus data to index word frequency.

The discrepancy between these two studies suggests that adult frequency counts may be unsuitable for creating an effective manipulation with children. Blythe et al. (2009), however, did find robust frequency effects in children aged 7- to 9-years and 10- to 11-years across two separate experiments that used adult frequency counts in the target word manipulation (the disappearing text study outlined in Section 5.2). These effects occurred in very early measures of lexical identification, single and first fixation durations, in both children and adults. A third study that used adult frequency counts also found effects on 8- to 10-year-old children’s eye movements, but only in gaze durations and total reading times (Huestegge et al., 2009). There was a numerical trend for longer first fixations on low frequency words compared to high frequency words, but this was not statistically significant. Unfortunately this study did not include a control group of adults, and so it is not possible to gauge how effective this manipulation of frequency was for skilled adult readers in comparison to children.

Overall, word frequency appears to exert a strong influence on the ease of lexical identification, as indexed by eye movement measures, from 7-years of age. It may, however, be the case that while it is possible for adult counts of frequency to generate effects in children (many words are, of course, high or low in frequency for adults and children alike), using frequency counts from age-appropriate texts is a more reliable means of obtaining robust effects. There is a clear need for a study to manipulate both adult and child frequencies and to examine whether they differentially affect eye movement behaviour in readers of different ages. Future research will also benefit from the careful control of potentially confounding linguistic variables such as Age-of-Acquisition and predictability, as well as the age-appropriateness of the texts used to index frequency, in order to establish more firmly how word frequency affects children’s ongoing lexical processing. Finally, it should be noted that these data provide extremely strong evidence for cognitive control of eye movements during reading in children as young as 7-years. That is to say, by the age of 7-years, children’s reading has developed to a level where their linguistic processing of the fixated word determines when they move their eyes on through the text.

7. Post-lexical processing

Only one study, to our knowledge, has used eye-movements during reading to examine children’s processing during reading at a post-lexical level. Joseph et al. (2008) investigated how children (aged 7- to 11-years) and adults processed implausible and anomalous thematic relations during reading (see also the chapter by Warren in the current volume). In their experiment, participants read sentences such as (1a-1c) below. The sentences described events in which an individual performed an action with an instrument. In each case, the verb had three thematic roles (see sentences 1 a-c): an agent (Robert), an instrument (trap, hook or radio) and a patient / theme (mouse).

1a. Robert used a trap to catch the horrible mouse that was very scared.

1b. Robert used a hook to catch the horrible mouse that was very scared.

1c. Robert used a radio to play the horrible mouse that was very scared.

In all three sentences the instrument (trap, hook or radio) could be plausibly used in conjunction with the main verb (catch or play). In the implausible condition (1b), however, the patient (mouse) was incongruous as the object of the verb (catch) given the particular instrument used (hook). That is, although hooks are often used to catch things (e. g., fish), and mice are often caught, a hook is not often used to catch a contrast, in the anomalous condition (1c), the patient (mouse) could not be used in conjunction with the verb (in this case play).

Joseph et al. found that while children did not differ from adults in their anomaly detection (both groups exhibited longer gaze durations on the critical word in the anomalous than control conditions), they were delayed relative to adults in their implausibility detection. Adults showed disruption in go-past time (the sum of all the temporally contiguous fixations from the first fixation in a region until a fixation to the right of the region) in the post-target region, while children only showed disruption in total time in the post-target region. Thus, there was a difference in the time course of the disruption. The authors interpreted the data as showing that children and adults were similar in terms of basic thematic assignment processes that occur during reading, but that they differed in the efficiency with which they were able to integrate pragmatic and real world knowledge into their discourse representation.

While it is difficult to make any firm conclusions based on data from a single study, the results from Joseph et al. (2008) suggest that in some respects children may be adult-like in their post-lexical written language comprehension, although they appear to be slower than adults to incorporate real world knowledge information into their representation of sentence meaning. Clearly, much more research is needed before this claim can be more than speculative. If correct, however, this would suggest that early in reading development, children are very similar to adults in terms of the oculomotor mechanisms they have in place in order to make the eye movements necessary for written language comprehension, but that the efficiency and speed with this these mechanisms and processes function is reduced relative to adult reading performance. It may also be the case that there are developmental differences in how post-lexical processing influences eye movement control.

8. Future directions

Overall, despite the small number of studies that have investigated children’s eye movements during reading, we believe great progress has been made towards understanding oculomotor control and on-line written language comprehension in children. This is an exciting time in the field of developmental eye movement research into reading, as technological improvements rapidly open up more possibilities for conducting well-controlled and innovative experiments with children. There are several directions in which we anticipate the field will head in the future.

First, we believe that will be both timely and informative for new studies to examine the relative contributions of variables such as chronological age, reading age, and IQ to the development of oculomotor control during reading. From the existing literature on eye movements during reading, the large variance in children’s data suggests that such factors are recording the broader cognitive profiles of children with respect to their language and literacy development, and analysing such information in relation to their eye movement data, we hope that research will allow a more detailed understanding of the relationships between development with age, reading skill and the moment-to-moment cognitive processing of text as indexed by eye movements.

Second, we hope that the use of portable, highly-accurate eye tracking equipment will enable well-controlled, longitudinal studies to be carried out. All of the research conducted in the field thus far has been cross-sectional in design. While this work has proved extremely informative, longitudinal studies will allow a more detailed examination of the developmental trajectory of reading behaviour in relation to different aspects of linguistic processing. This approach is already standard in studies using off-line measures of reading comprehension (e. g., Muter, Hulme, Snowling, & Stevenson, 2004; Nation & Snowling, 2004). By adopting similar experimental designs and using an on-line measure of cognitive processing as it occurs during reading, researchers will be able to advance current understanding of literacy development by taking a range of variables into account that differ within typically developing children.

Third, there has only been one published study which has examined linguistic effects beyond the lexical level in children (Joseph et al., 2008). Further studies are needed to investigate aspects of higher order linguistic processing (e. g., syntactic and semantic processing, and even discourse processing) in children during sentence reading. While research thus far has shown that adults and children from the age of 7-years are very similar in their processing of visual linguistic stimuli at a lexical level, we consider it entirely possible that research examining post-lexical processing will reveal developmental changes that continue beyond the age of 7-years. One issue that may arise in relation to manipulations of higher order linguistic processing in children is that of stimulus selection. It is not yet clear whether the use of higher-level linguistic manipulations which have generated robust processing preferences in adult readers will produce reliable effects in children. For example, given the increased variability introduced by including children as participants, it may be that manipulations which result in small effect sizes in adult readers (e. g., lexical ambiguity effects) will not produce detectable effects in children.