KARINE GAUTHIER
B-F
E b
G-EFFECT OF INFORMATION PROCESSING SLOWNESS ON READING COMPREHENSION SKILLS AMONG TRAUMATIC BRAIN INJURED
CHILDREN
Mémoire présenté
à la Faculté des études supérieures de Γ Université Laval
pour Eobtention du grade de maître en psychologie (M. Ps.)
École de psychologie
FACULTÉ DES SCIENCES SOCIALES UNIVERSITÉ LAVAL
DÉCEMBRE 2002
Les habiletés de lecture peuvent être sérieusement compromises par un traumatisme cranio-cérébral (TCC) vécu pendant l’enfance. Toutefois, peu d’études ont porté spécifiquement sur ce type d’habiletés à la suite d’un TCC, laissant ainsi la nature des déficits de lecture à clarifier. Ce projet de recherche examine l’influence de la vitesse du traitement de !’information, des habiletés de décodage et de la conscience phonologique sur les compétences en compréhension de lecture d’enfants ayant subi un TCC modéré ou sévère. Cette étude démontre que les enfants ayant subi un TCC (n = 27) présentent une performance significativement plus faible dans une tâche simple de compréhension en lecture comparativement aux enfants qui n’ont jamais subi de TCC (n = 27). De plus, les résultats démontrent que les enfants TCC sont significativement plus lents pour décoder ainsi que moins efficaces dans des tâches impliquant la conscience phonologique comparativement au groupe contrôle.
ABSTRACT
Reading abilities can be seriously compromised by a traumatic brain injury (TBI) in childhood. However, only a few researchers have specifically studied these types of abilities following a TBI, leaving nature of reading deficits unclear. This research project examines the influence of speed of information processing, decoding abilities and phonological awareness on reading comprehension deficits among children who sustained a moderate or severe TBI. The performance of a TBI group (n = 27) was compared to the one of 27 control children. This study demonstrated that TBI children present a significantly lower performance on a simple reading comprehension task, compared to children who have never experienced a TBI. Furthermore, the results showed that TBI children are significantly slower in decoding and less efficient in a task involving phonological awareness as compared to non-injured children.
Plusieurs personnes ont permis la réalisation de ce projet de recherche. J’aimerais tout d’abord remercier mon directeur, Monsieur Michel Pépin, pour ses précieux conseils et son support. Il m’a aidé à développer mes aptitudes en recherche ainsi que mon autonomie. Je tiens également à souligner le support financier du Conseil de Recherches en Sciences Naturelles et en Génie du Canada (CRSNG).
Je désire également exprimer ma reconnaissance aux enfants et parents qui ont accepté de participer à cette étude. De plus, je remercie grandement le personnel des écoles et organismes suivants pour leur aide inestimable dans le recrutement des participants: l’École l’Apprenti-Sage, l’École du Trait-d’Union, l’École le Privent, l’École Bon-Pasteur, l’École de la Fourmillière, l’École de l’Aubier, l’École De Léry- Mgr-De Laval et le Patro de Charlesbourg. Je veux également souligner l’apport précieux du Centre de réadaptation Marie-Enfant de l’Hôpital Sainte-Justine, de l’Institut de réadaptation en déficience physique de Québec, site Cardinal-Villeuneuve, du Centre de réadaptation Estrié inc. et du Centre de réadaptation Interval dans le recrutement des enfants ayant subi un traumatisme cranio-cérébral. De plus, je remercie Sandra Hoops pour le service rapide et efficace de correction de l’anglais qu’elle m’a offert. Par ailleurs, je tiens à souligner l’aide de monsieur Marquis Falardeau lors de la création de la base de
données.
Je veux remercier mes parents et mes amis(es) pour leur support et leur compréhension tout au long de la réalisation de ma maîtrise. Je tiens également à souligner l’apport précieux de Jonathan dans ce projet. Il a su m’encourager et me soutenir d’une façon exemplaire. Qui plus est, il m’a grandement aidé en me créant sur mesure un logiciel de compilation de données.
TABLE OF CONTENT Page RÉSUMÉ... ii ABSTRACT... ... iii AVANT-PROPOS... iv TABLE OF CONTENT... v
TABLES LIST... vii
1. GENERAL INTRODUCTION ... 1
1.1 Traumatic brain injury... 2
1.2 Speed of information processing... 3
1.3 Decoding abilities... 5
1.4 Phonological awareness... 6
1.5 Reading comprehension... 6
2. ARTICLE: EFFECT OF INFORMATION PROCESSING SLOWNESS ON READING COMPREHENSION SKILLS AMONG TRAUMATIC BRAIN INJURED CHILDREN 2.1 Title page... ... 10
2.2 Speed of Information Processing following a Traumatic Brain Injury... 11
2.2.1 Toward an understanding of information processing slowing in TBI children... 13
2.3 Reading Abilities Following Traumatic Brain Injury... 14
2.4 Speed of information processing and reading... 16
2.5 Effect of age at the time of the TBI... 18
2.6 Objectives and hypotheses... 19
2.7 Method... 20
2.7.1 Participants... 20
2.7.2 Procedure and tests...:... 21
2.7.2.2 The Test d’habiletés en lecture... 24
2.7.2.3 The TAI-Enfants... 25
2.8 Results... 26
2.8.1 Difference between groups for motor speed... 26
2.8.2 Difference between groups for comprehension abilities... 27
2.8.3 Differences between groups for the processing speed variable... 27
2.8.4 Correlations between speed of information processing and reading comprehension abilities... 27
2.8.5 Effect of age at the time of TBI on reading comprehension abilities.. 28
2.8.6 Correlations between early indices of severity of injury and performance in reading comprehension... 28
2.8.7 Gender differences... 29
2.9 Discussion... 29
3. GENERAL CONCLUSION... 34
4. ARTICLE’S REFERENCES... 36
5. COMPLETE REFERENCE LIST... 42
6. APPENDIX A: Formulaire d’information et de consentement (groupe TCC)... 55
7. APPENDIX B : Formulaire d’assentiment (groupe TCC)... 61
8. APPENDIX C: Formulaire d’information et de consentement (groupe contrôle)... 62
Vil
TABLES LIST
Page Table 1. Demographic data of the TBI and control groups... 51 Table 2. Performance variables for the TBI and control group... 52 Table 3. Correlations between information processing speed measures and
number of correct responses on the comprehension subtest for TBI
and control groups... ... 53
Table 4. Correlations between early indices of injury severity (length of impaired consciousness and GCS) and performance in
traumatic brain injury (TBI)1 sustained during childhood (Anderson, Catroppa, Rosenfeld, Haritou, & Morse, 2000; Fletcher & Ewing-Cobbs, 1991). The frontal lobes' development is especially vulnerable to TBI (Nybo & Koskiniemi, 1999). The development of this part of the brain is greatest during the first five years of life (Hudspeth & Pribram, 1990) and continues until the age of 16 (Thatcher, 1991). Thus, a child who sustained a moderate or severe TBI is likely to present several cognitive problems (Chadwick, Rutter, Brown, Shaffer, & Traub, 1981; Winogron, Knights, & Bawden, 1984), and some of these problems will appear only later in the child's development (Oddy, 1993). Such cognitive deficits can cause academic difficulties, one of the most serious consequences of TBI (Goldstein & Levin, 1985; Jaffe et al., 1993). In fact, decreased academic performance and transfers to special classes are frequent outcomes for children who experienced a TBI (Bonders, 1994; Ewing-Cobbs, Fletcher, Levin, lovino, & Miner, 1998; Shaffer, Bijur, Chadwick, & Rutter, 1980).
Childhood traumatic brain injury (TBI) can seriously compromise reading abilities (Shaffer et ah, 1980; Wrightson, McGinn, & Gronwall, 1995). However, only a few researchers have specifically examined these types of abilities following a TBI, leaving reading deficits' nature unclear (Barnes, Dennis, & Wilkinson, 1999). Some authors have suggested that the speed of word recognition could affect reading comprehension (Barnes et ah, 1999; Perfetti, 1985). Furthermore, some studies have demonstrated that following a TBI, children tend to be particularly weak in timed tasks (Bawden, Knights, & Winogron, 1985; Chadwick, Rutter, Shaffer, & Shrout, 1981). Kinsella and his colleagues (1995) have suggested that the speed of information processing deficits could disturb a child’s everyday life, particularly in school where speed when completing tasks is the key to success.
The main purpose of this study is to better understand reading comprehension deficits in children who experienced a moderate or severe TBI. More precisely, this
Effect of information processing slowness 2
research is designed to examine the influence of speed of information processing, decoding abilities and phonological awareness on reading comprehension deficits among TBI children. This study also attempts to determine the impact of age at the time of TBI on reading comprehension abilities.
It seems important to clarify the nature of the problems that are susceptible to influence reading comprehension in TBI children in order to give an appropriate intervention to improve their condition. Eventually, it could be possible to better prevent the occurrence of those problems and to better adapt the school environment. Moreover, the fact that reading comprehension capacities are highly correlated to academic success (Fuld & Fisher, 1977) makes them even more pertinent to study.
Before presenting a review of the literature on the role of speed of information processing, decoding speed and phonological awareness in reading comprehension deficits among TBI children, it is important to clearly define each variable examined in the present study. Thus, the next section will define and explain the following concepts: traumatic brain injury, speed of information processing, decoding abilities, phonological awareness and reading comprehension.
Traumatic Brain Injury
A TBI is an acquired cerebral injury provoked by an external physical force that is susceptible to cause a diminished or altered state of consciousness. This condition can be associated with perturbations of the cognitive functions associated or not with a physical dysfunction (Gadoury, 1999). Behavioural and emotional changes may also be observed. The term applies to open or closed head injuries, but is not relevant to brain injuries that are degenerative or congenital.
The most frequent mechanism by which TBI occurs is acceleration-deceleration and rotational injuries (McNair, 1999). An acceleration-deceleration injury is provoked by a sudden change in speed. The brain, being lighter than the skull, moves slower and impacts the inside surface of the skull (McNair, 1999). Furthermore, the different
structures of the brain have their specific masses and volumes, making them move at different speed while the brain is in motion (Oddy, 1993). The faster moving structures stretch and tear away from the slower parts. The brain may also rotate, causing shearing of brain tissue particularly at the brain stem and reticular activating system.
Three pathologic mechanisms are involved in the clinical presentation of the TBI: primary injury, secondary injury and complications. Primary injuries occur at the time of the impact. They include fracture, contusion, diffuse axonal injury, subarachnoid hemorrhage, as well as epidural, subdural and intracerebral hematomas. Secondary injuries happen following the initial injury. They consist in cellular and axonal degeneration, cerebral oedema, anoxia or hypoxia. Finally, complications include infection, hydrocephalus, cortical or subcortical atrophy, epilepsy and headache. Thus, TBI can engender many different lesions or medical problems. Knowing this permits to better comprehend why outcomes of a TBI can be so diverse and complex.
Approximately 1 million children sustain a TBI each year in the United States (Lehr, 1990; Lord-Maes & Obrzut, 1996). Over the past 10 years, advancement in technology and medicine increased the chance to survive a TBI (Leuenberger, 1998). Thus, more children who sustained a moderate or severe TBI survive and reintegrate their home and school. It appears to be very important to better understand the problems they will probably experience to permit better treatments and more appropriate adaptation of the environment. The next section introduces some variables that could be affected by a TBI.
Speed of information processing
According to Whyte (1992), speed of information processing is described as “the rate at which incoming information is processed to reach action decisions”. This author suggested that speed of information processing is a component of the Attention System also formed by arousal, selective attention and strategic control of attention. Whyte mentioned that slowness of information processing can result in underlying problems such as diminished arousal and inappropriately directed attention. Other authors have also
Effect of information processing slowness 4
suggested that information processing slowness often underlies attentional problems (K10ve, 1987; van Zomeren, Brouwer & Deelman, 1984).
Weber (1990) also made a link between information processing and attention. He suggested that there are two basic dimensions of deliberate attention: Capacity and
Control. Capacity represents the quantity of information that can be attended to within a
certain time. According to Weber, the terms attentional capacity and information processing capacity have the same meaning because the quantity of information that can be processed in a given time is similar to the amount that can be attended to in a system with limited capacities. The fact that the system has a limited capacity, leads on the one hand, to the experiencing of a mental effort and on the other hand, to a selection of the information to be attended to. Finally, Control refers to the capacity to direct and organize attentional capacity. There is interdependency between Capacity and Control. In fact, because the capacity is limited, it is essential that the selection of information be done efficiently.
Moreover, information processing speed seems to influence the efficiency of the working memory. Jensen (1982) and Vernon (1985) suggested that all intellectual activities need some sort of working memory system to be effectively accomplished. However, working memory system has a limited storage capacity and is not able to store information for an extended period of time without sustained rehearsal. Furthermore, the system must divide its resources between the amount of information that it can hold and the quantity of information that it is able to process at the same time. According to these limited capacities, speed of information processing is of first importance. In fact, the faster the information is encoded and analysed into working memory, the higher the probability that the system will not be overload (Vernon, 1990). At each stage of problem solving, the faster the required processes can be accomplished, the less likely the system will attain its threshold and consequently, the higher the probability that the problem will be solved adequately.
The speed of information can also be influenced by personality characteristics such as Carefulness, Persistence, and Impulsivity (Hunsicker, 1925). Those factors would influence the trade-off between speed and accuracy. The probability that a trade-off between speed and accuracy will influence performance is higher when the task to complete is complex (Lohman, 1989).
Decoding abilities
For Robeck and Wallace (1990), decoding abilities are the processes by which letter symbols are translated into meaningful language. Three steps are needed for children to achieve decoding: 1) discrimination and identification of each visual unit, 2) association of good sound units with each visual part, and 3) combination of sound elements to obtain known words. For skilled readers, this process is rarely used because words are recognized as a whole by using a lexicon. This lexicon is built as the reading experience increases. Backman, Brack, Hebert and Seidenberg (1984) suggested that at age 9 or 10 a child is able to read lexically irregular words without doing a graphem- phonem conversion.
Decoding speed has been linked to reading difficulties. Bowers (1993) proposed that the slowing down in naming simple visual material like letters or digits could explain the performance of poor readers. More precisely, this slowness could be responsible for their delays in recognizing orthographic units and their lack of aptitude to store word- specific orthographic codes. Other authors have suggested that symbol-naming speed as well as phonological awareness seem to contribute partially and independently to reading disabilities (Felton & Brown 1990; Lovett, 1987). Furthermore, there is a high positive correlation between letter-naming speed and the time taken to correctly identify single words (Bowers & Swanson, 1991). According to Stanovich (2000), good readers recognize words automatically and rapidly. This applies for direct visual identification or phonological recoding.
Effect of information processing slowness 6
Phonological awareness
Phonological awareness represents the awareness of sound structures in speech. This concept should not be confused with phonemic awareness, which is the knowledge of phonemic structure of words. Barnes and Denis (1992) describe phonemic awareness as “an early phonological skill conferring the knowledge that words are made up of units of sound”. Phonological awareness is a broader concept that includes phonemic awareness.
Phonological awareness is an important component of the child’s reading development (Juel, 1988; Lundberg, Frost, & Petersen, 1988). According to Adams (1990), skilled reading depends on an automatic capacity to visually identify common spelling patterns and to phonologically translate them. If this process is not automatic, the reader spends too much time and attention on identifying each individual word, phoneme or syllable. Because attentional capacities are limited, if too much energy is invested into those basic tasks, the reader will not have enough attention focused on text comprehension.
A study of Wimmer, Maryringer and Landed (1998) with German dyslexic children demonstrated that problems in learning to read are engendered by phonological deficits and not by a general skill-automatization deficit. Thus, phonological awareness seems to play an important role in reading.
Reading comprehension
The objective of reading is to understand written material. Several abilities are involved in the comprehension process: visual analysis, word decoding, mnemonic retrieval of word meaning, syntactic and semantic analysis, interpretation of texts, use of contextual cues and inference making. Three theoretical approaches to reading comprehension deficits proposed by Oakhill (1993) will be presented in the next paragraphs.
The first theory concerns the single-word level. According to the Perfetti’s bottleneck hypothesis (1985), speed and automaticity of words decoding have an important role in reading comprehension deficits and individual differences in reading comprehension can be related to those processes. This approach assumes that decoding and comprehension processes are in competition to obtain limited short-term memory resources.
In a study of Nicholson and Tan (1999), 42 children from 7 to 10 year-old who had poor word identification and reading comprehension skills were trained to decode words faster. After the training, the participants read faster and were better in reading comprehension. This study proposed a causal link between speed of decoding and reading comprehension. The obtained results supported the bottleneck hypothesis.
Thought many studies suggested that readers with poor comprehension skills are slow decoders, there are fast decoders with poor comprehension, and vice versa. This demonstrates that problems in decoding speed and automaticity do not suffice for a comprehensive explanation of reading comprehension problems. Along similar lines, Just and Carpenter (1987) suggested that rapid word recognition speed is not sufficient for good reading comprehension.
A second theoretical approach suggests that reading comprehension difficulties are due to problems in the syntactic and semantic analysis of text. This approach argues that readers with comprehension difficulties do not use syntactic constraints in text and have a tendency to read word-by-word rather than process text significant units (Cromer, 1970; Oakan, Wiener & Cromer, 1971).
According to the last theory, comprehension deficits are due to difficulties regarding higher-order comprehension abilities such as making inferences, integrating ideas in text, and monitoring comprehension (Oakhill, 1993).
Effect of information processing slowness 8
Because reading comprehension depends on many cognitive processes, it is likely that all the factors implied in the aforementioned theoretical approaches play an important role in the children’s reading comprehension difficulties. TBI children are a very specific type of population that present particular cognitive and linguistic problems. Thus, it is important to determine whether or not they present reading comprehension deficits and if so, to investigate the possible causes of these deficits.
Effect of information processing slowness 10
Running head: READING COMPREHENSION IN TBI CHILDREN
EFFECT OF INFORMATION PROCESSING SLOWNESS ON READING COMPREHENSION SKILLS AMONG TRAUMATIC BRAIN INJURED CHILDREN
Karine Gauthier and Michel Pépin Université Laval, Quebec, Canada
Reading abilities can be seriously compromised by a traumatic brain injury (TBI)1 sustained in childhood (Shaffer, Bijur, Chadwick, & Rutter, 1980; Wrightson, McGinn, & Gronwall, 1995). However, only a few researchers have specifically studied these types of abilities following a TBI, leaving a void in the comprehension of reading deficits (Barnes, Dennis, & Wilkinson, 1999). Some authors have proposed that speed of word recognition could affect reading comprehension (Barnes et al., 1999; Perfetti, 1985). Furthermore, some studies have demonstrated that following a TBI, children tend to present a slowness of information processing (Bawden, Knights, & Winogron, 1985; Chadwick, Rutter, Shaffer, & Shrout, 1981). Kinsella and his colleagues (1995) have suggested that speed of information processing deficits could disturb a child’s everyday life, particularly in school where speed when completing tasks is the key to success.
The next section is divided into four parts. First, the effects of TBI on speed of information processing are presented, along with an explanation of those effects. Second, research about how reading abilities are affected by a TBI during childhood is described. Third, the influence of slowed information processing on reading abilities is discussed. Fourth, studies about the impact of age at the time of TBI on cognitive and reading abilities are presented.
Speed of Information Processing following a Traumatic Brain Injury
Speed of information processing is an important variable to consider among people who have sustained a TBI since it is associated with their functional outcomes and employability (Asikainen, Nybo, Müller, Sarna, & Kaste, 1999). Indeed, Asikainen and colleagues' longitudinal study showed that the participants who where slowest to complete the Stroop Test had a lower score on the Glasgow outcome scale (GOS) and inferior employability capacities. Kinsella and collaborators (1997) found that speed of information processing is one of the potential contributors to the prediction of education placement following a mild, moderate or severe TBI sustained in childhood. Along similar lines, a study by Ruff and collaborators (1993) demonstrated that speed of
Effect of information processing slowness 12
information processing, verbal intellectual capacities and age were the three most powerful predictors of a return to school after a severe TBI.
In a study by Chadwick, Rutter, Shaffer and Shrout (1981), 25 children with severe head injury were compared to 25 children with orthopaedic injuries. The children were evaluated two to four weeks, 4 months, 1 year and 21/4 years after the injury. At the first evaluation, TBI children showed deficits on nearly every neuropsychological test. Improvement was observed on many tests during the first year. After 21/4 years, the only deficits found were on the WISC-R IQ test Performance scores, the Manual Dexterity Task, and a copying task. These three tasks require speed to be efficiently completed, as well as visuospatial and visuomotor skills.
Other researchers have suggested that the ability of TBI children to respond quickly could affect their performance in cognitive tasks such as the Performance subtests of the WISC-R (Jaffe et al., 1993; Winogron, Knights & Bawden, 1984). Deficits on the performance subtests can be explained by their demands for rapid performance under time pressure and their complexity. More recently, Hoffman, Donders, and Thompson (2000) compared the WISC-III index scores (Verbal Comprehension, Perceptual Organization, Freedom from Distractibility and Processing Speed) between a group of children who sustained a severe TBI (n = 28) and a group composed mostly of children with mild TBI (n = 35), and also some others with moderate TBI (n = 6). The mean injury-testing interval was 82,96 days. The authors confirmed that children who sustained a severe TBI present significant deficits in speed of information processing. In fact, among the four indexes, only the Processing Speed index was significantly different between both groups. This finding suggests that speed of information processing is a very important variable to consider following a severe TBI.
Furthermore, people who sustained a TBI, present progressive slowness of information processing with increased task complexity. This has been demonstrated by comparing simple and choice reaction times among young males (van Zomeren & Deelman, 1978). This phenomenon has also been observed as the child advances
academically. In fact, as the complexity of the material increase from one grade to another, the TBI child often presents a drop in performance as compared to his or her peers (Braga & Campos da Paz, 2000).
According to Hetherington, Stuss and Finlay son (1996), the slowness of information processing following a TBI is observed primarily in the encoding of stimuli and in the selection of an answer. Some studies demonstrated that the slowness in the selection of an answer can persist in the chronic phases of TBI (Shum, McFarland, & Bain, 1994). Furthermore, any efficacy reduction in the processing of the elementary psychological processes can result in performance gaps during complex tasks. Van Zomeren, Brouwer and Deelman (1984) suggested that the deficits in complex tasks characterized by a demand of focused attention or divided attention deficits could be caused by a cognitive slowness.
Together, these studies show that deficits in speeded performance are frequently found among children who sustained a TBI. However, none of these studies have clearly distinguished motor speed from mental speed. Motor speed is an important point to consider since it is often diminished among victims of moderate or severe TBI (Bawden et al.,1985; Haaland, Temkin, Randahl, & Dikmen, 1994; Jaffe, Polissar, Fay, & Liao, 1995). Consequently, if the influence of this variable on speed of information processing is not measured, the picture is not complete. The present study measure motor speed to assure that the slowness of information processing in TBI children is not due to a motor slowness.
Toward an understanding of information processing slowness in TBI children
Some explanations of information processing slowness observed in TBI victims have been proposed. Brouwer (1985) suggested that the degree of information processing slowness following a TBI is related to the task's recall demands. According to this researcher, recall problems primarily affect the use of knowledge from the verbal memory. The cognitive theories of Anderson (1993; 1976) propose that all human acts require a recall of information stocked in the declarative memory. These theories also
Effect of Information processing slowness 14
suggest that declarative knowledge can be represented by an associative network of several interconnected nodes. If the activation threshold of a node is reached, the information it contains becomes available. The nodes’ activation and the links’ strength increase every time they are used. The speed of knowledge recall from the declarative memory is strongly determined by the degree of nodes’ activation and by the strength of the links that unify them. Mental slowness following TBI could therefore result in a global decrease of associative strength between nodes, likely due to a diffuse functional or structural loss of axonal tissues (Brouwer, 1985; van Zomeren & Brouwer, 1987). In fact, diffuse axonal, or white matter injury, is the most common types of brain damage in TBI (Stuss & Gow, 1992). Along similar lines, Tromp and Mulder (1991) proposed that reduced associative strength between concepts stored in memory could affect the speed with which related knowledge can be accessible or recalled.
Reading Abilities Following Traumatic Brain Injury
A study of Ewing-Cobbs, Fletcher, Levin, Iovino, and Miner (1998) demonstrated that children who sustained a severe TBI performed worse in reading comprehension than those who suffered mild to moderate TBI. Reading comprehension was measured by the reading comprehension subtest of the Peabody Individual Achievement Test (Dunn & Markwardt, 1979). An improvement, although not significant, was noted in reading comprehension scores between baseline and the 6-month follow-up. However, performance was stable from 6 to 24 months after the TBI. Moreover, the performance of children with severe head injuries was significantly lower on the reading recognition subtest of the Wide Range Achievement Test (WRAT; Jastak & Jastak, 1978). This study also examined the academic placement of the patients. Seventy-nine percent of the severely injured patients required resource assistance, received a modified curriculum or failed a grade. Reading and language arts were the two fields in which resource assistance was most often received.
A longitudinal study by Prior, Kinsella, Sawyer, Bryan, and Anderson (1994) found that children who sustained a moderate to severe head injury performed more poorly than mildly injured children on word recognition measures of the Wide Range Achievement
Test-Revised (WRAT-R; Jastak & Wilkinson, 1984). The evaluations were carried out 3 to 16 weeks after the date of injury and at a 6-month follow-up. The children's performances did not show improvement over time.
Contrary to the previous findings, Perrot, Taylor, and Montes (1991) found no difference on the WRAT between children who sustained a moderate to severe TBI and a control group made up of their siblings. These results could be explained by the long interval between TBI and testing (17 to 68 months after their injury), as compared to the studies mentioned above.
Shaffer and collaborators (1980) studied reading ability in a sample of 88 children who sustained a compound depressed fracture of the skull involving damage to the cortex. The Neale Analysis of Reading Ability (1958) was used to evaluate reading accuracy and reading comprehension. Since the two abilities were highly correlated (r = .94, p < .001) and because there was a similar distribution of discrepant scores, the authors decided to use just one of the measures to evaluate reading backwardness. They chose reading accuracy because more scores were available. The results demonstrated that 55 % of the children had reading ages that were 1 or more years behind their chronological ages, and 33 % were 2 years behind. No significant association was found between age at injury and reading delays. This study did not involve a control group because it was designed to examine within-group differences. Nevertheless, the authors compared their results to those of Berger, Yule, and Rutter (1975), who studied reading backwardness in noninjured children using similar criteria. The rate of reading backwardness in the brain-injured children was significantly higher than that of the noninjured sample.
Reading deficits have also been found in children who sustained a mild TBI. A study by Wrightson and colleagues (1995) compared 78 children who sustained a mild head injury to 86 children with a minor injury elsewhere. No difference was found in the first month after injury between the two groups on a test of visual closure, in which the child had to rapidly find objects hidden in pictures. However, the performance of children
Effect of information processing slowness 16
who sustained a mild head injury was poorer than that of the control group at 6 and twelve-months post-injury. Upon evaluation at 6.5 years of age, the mild head injury group scored significantly lower than the control group on the visual closure test, and their performance on this test was related to their reading abilities, as evaluated by the Neale Analysis of Reading Ability (1966). The mildly injured group also needed more help with reading during their first year.
Furthermore, Ylvisaker (1981) found that 90 % of teachers who work with TBI children report that these students experience a relatively severe deterioration in reading comprehension - relative to expectations for the class - as text size increases. Twenty-five percent of those teachers also report that these children have deficits in reading individual words.
Thus, many studies found reading deficits among children who sustained a TBI. However, within the studies just mentioned, none specifically tried to understand the etiology of comprehension deficits in children following a TBI. The next section presents an explanation for reading comprehension deficits and describes a study that tests this hypothesis among TBI children.
Speed of information processing and reading
To possess the energy and cognitive resources necessary to understand a text, readers must make use of rapid and automatized processes so that little effort is require to recognize and understand a text (Adams, 1990). Good readers have well-developed word recognition abilities, enabling them to read more than five words per second (Rayner & Pollatsek, 1987).
Some authors have proposed that speed of word recognition could affect reading comprehension (Barnes et ah, 1999; Perfetti, 1985). The Perfetti bottleneck hypothesis proposes that decoding and comprehension processes compete to obtain the limited resources of the short-term memory. If one of the processes does not work optimally, the other cannot operate correctly. Thus, slowed word decoding could lead to an inadequacy
of processing resources to facilitate the integration and comprehension of a text. Nelson and Schwentor (1991) mention that TBI victims are particularly at risk to experience reduced reading speed. According to these authors, this diminution in reading speed could be due to visuoperceptual problems, mental slowness, use of time-consuming strategies to better understand texts, or a reduction of understanding of text organization and structure. A study by Barnes and collaborators (1999) made a link between slowed information processing and reading among TBI children.
This study demonstrated that children who experienced a TBI were slower than control subjects to read words of many kinds: regular words, regular inconsistent words, ambiguous words, exception words and strange words. The rate of correct responses did not differ between the TBI and the control group, suggesting that variations in response time between the groups are not due to a trade-off between speed and accuracy (Barnes et ah, 1999). There were no significant differences between both groups in term of time taken to pronounce non words.
The authors used multiple regression to determine the relative importance of word recognition adequacy and speed in reading comprehension. The results showed that these two variables account for 44 % of score variance in reading comprehension among children who sustained a TBI. The authors mention that even if a slowness of word processing characterizes reading following a TBI in childhood, precision and speed only account for less than half of the variance in the scores of the TBI group. This suggests that other linguistic abilities, such as phonological awareness or the capacity to make inferences, can contribute to the reading difficulties experienced by children who sustained a TBI. In fact, it as been demonstrated that the capacity to infer is often deficient following a childhood TBI (Dennis & Barnes, 1990). By using a simple comprehension test that does minimally require the child to make inferences, the present study intends to isolate the effect of a slowness of information processing, as well as decoding and phonological abilities. Thus, it will be possible to better identify the actual influence of those variables on reading comprehension.
Effect of information processing slowness 18
Barnes and collaborators’ sample of TBI subjects is heterogeneous with respect to injury severity and this constitutes a limitation of their study. The study includes children who experienced mild, moderate and severe TBI and the researchers do not distinguish moderate-severe TBI from mild TBI. In fact, these subgroups of TBI patients make up distinct populations insofar as they contain individuals with significantly different neuropsychological profiles. With this fact in mind, Asikainen and collaborators' (1999) excluded patients with mild TBI because they were not representative of the broader group. Indeed, compared to the patients who sustained a moderate or severe TBI, people with mild TBI are often less referred to rehabilitation services and present a better recovery capacity. To better determine the real extent of the problems that can occur following a TBI, it is preferable to study a relatively homogeneous group concerning the injury severity. Thus, the present study only includes children who suffered a moderate or severe TBI.
Effect of age at the time of the TBI
Some studies demonstrate that following a TBI, children have better chances of recovering than older persons because of the better adaptation capacities of their young brain (Bower, 1990; Chugani, Muller, & Chugani, 1996). Nevertheless, other studies, like that of Asikainen, Kaste and Sama (1996), reported that a better outcome was associated with individuals who experienced their TBI around the end of their adolescence or at an adult age. Along similar lines, Asikainen and collaborators (1999) mentioned that children who sustained a TBI at the age of seven years or less do not present a better recovery capacity than older children.
A study by Barnes and collaborators (1999) demonstrated that children who sustained a TBI before the development of decoding abilities or while the acquisition of these abilities during their first years of school, are more at risk for developing difficulties acquiring basic decoding skills and reading comprehension proficiency. Indeed, children who experienced a TBI before the age of nine showed less developed decoding and reading comprehension abilities than children who sustained a TBI after the age of nine.
Shaffer and colleagues (1980) found that more reading disorders were present among children who sustained a TBI before the age of eight than in those who were older at the time of injury. In the study by Ewing-Cobbs and collaborators (1998), children who sustained their TBI between 5 and 10 years of age improved less in their reading scores than those who experienced a TBI between the ages of 10 to 15 years.
Barnes and his colleagues (1999) proposed that access to the knowledge unified by the weakest links in the lexical system can be particularly vulnerable following childhood TBI. The rapid development hypothesis (Fletcher, Miner, & Ewing-Cobbs, 1987; Hebb, 1942) suggests that the abilities developing rapidly at the time of the TBI are more undermined than abilities that are better established. Since word-decoding abilities increase quickly during the elementary years, while reading comprehension development is extended over a longer period, a TBI can distinctly affect reading abilities, depending on the moment when it occurs (Ewings-Cobbs et ah, 1998). Along the same lines, a TBI seems to principally affect the acquisition of new abilities (Hebb) or abilities that are not completely acquired at the time of the TBI (Braga & Campos da Paz, 2000; Dennis, 1988).
Objectives and hypotheses
The main objective of this research project is to examine the influence of speed of information processing, decoding abilities and phonological awareness on reading comprehension deficits among children who sustained a moderate or severe TBI. The hypotheses of this research are the following: 1) Children who sustained a TBI will obtain a significantly lower performance score on a test that evaluates reading comprehension abilities than those who never suffered a TBI, 2) information processing speed, as measured by an aptitude test and a reading test, will be significantly lower among brain-injured children than in non-TBI children, 3) a negative relationship will be obtained between speed of information processing and the number of errors in the reading comprehension test. Thus, children whose information processing speeds are lowest will also make more errors in the reading comprehension test, and 4) children who suffered a TBI before or shortly after they acquire and master the basic read!
Effect of information processing slowness 20
(less than nine years of age) will perform more poorly in the reading comprehension test than children who suffered the TBI later in development. We chose the cut-off of 9 years because most children have acquired the necessary reading skills by this age. Indeed, according to McGee and Richgels (1990), the majority of children are considered to be accomplished readers by the end of their third grade, so around 9 years of age.
Method
Participants
This study involved two groups of children aged 6.9 to 13.3. The first group was composed of 27 children who sustained a moderate or severe TBI at the ages of 10 months to 11.4 years (Mean = 5.9 years, SD = 2.9 years). Fifty-seven percent of the families contacted agreed to have their child participate in the study. The rate of acceptance varied widely from one rehabilitation center to another, ranging from 0% to 96%. This fluctuation could be explained by the variety of communication media (e.g. letter, phone) from one rehabilitation centre to another. Furthermore, in the rehabilitation centre where nobody accepted to participate, a longitudinal study recruiting the same children started just before our study.
The classification of the TBI severity was based on the one proposed by Gervais and Dube (1999). According to this classification, a moderate TBI is characterized by a score of 9 to 13 on the Glasgow Coma Scale (GCS), a period of impaired consciousness lasting 30 minutes to 6 hours, a post-traumatic amnesia lasting one to 14 days, and lesions that are generally observable on CT Scans and Magnetic Resonance Imagery (MRI). A severe TBI implies a GCS score of eight or less, a period of impaired consciousness lasting six hours or more, post-traumatic amnesia lasting several weeks, and positive CT Scan and MRI results. An eight-month delay between the TBI and participation in this study was required in order to avoid measuring the short-term and transient effects of the TBI. The evaluation was performed an average of 4.2 years after the injury (SD = 2.3 years, range = .7- 8.5). Male participants (n = 18) outnumbered female participants (n = 9), reflecting what is usually seen in the TBI population (Kraus,
1995). GCS scores at the time of admission were documented in 25 of the 27 cases. Of these participants, 19 (70.4 %) had a GCS score of eight or less, while 6 had a GCS score between 9 and 13. The mean GCS rating was 7.12. The mean length of impaired consciousness, estimated from information provided in the medical records for 25 of the 27 participants, was 7.5 days. All but two of the 27 children showed brain lesions or observable brain damage, as demonstrated by a CT scan or an electroencephalogram (EEG). Data on PTA duration were rarely documented in the hospital records. Therefore, it was not taken into account when determining the severity of the injury. Using data on GCS scores, length of impaired consciousness, and lesions or objective damage, it was estimated that the TBI sample was made up of 5 moderate and 22 severe TBI victims. The causes of TBI included auto-pedestrian accidents (n = 11), motor vehicle accidents (n - 9), falls (n = 4), auto-bicycle accidents (n = 1), and other recreational activity accidents
01=2).
The control group was composed of 27 children who had never experienced a TBI. Those children were matched with the TBI subjects according to sex, age (±3 months) and parental socio-economic status. However, it was not always possible to match the children according to the last criteria since the schools that recruited the control group could not provide sufficient information to do so. Exclusion criteria for both groups were: 1) psychiatric or neurological antecedents, 2) previous history of intellectual deficiency or language problems, 3) premature birth, 4) serious motor or behaviour problems, 5) first language other than French. Statistical testing (ANOVAs) revealed that there were no significant differences in personal and socio-economic characteristics between the TBI group and the control group (table 1).
INSERT TABLE 1 ABOUT HERE
Procedure and tests
Participants of the TBI group were recruited following an archival search within four rehabilitation centres in the province of Quebec: Centre de réadaptation Marie
Effect of information processing slowness 22
Enfant de l’Hôpital Sainte-Justine (Montreal), Institut de réadaptation en déficience physique de Québec, Centre Cardinal-Villeuneuve (Quebec), Centre de réadaptation Estríe inc. (Sherbrooke), and the Centre de réadaptation Interval (Trois-Rivières, Drummondville, Shawinigan, Cap-de-la-Madeleine and Victoriaville). The primary investigator of this study consulted the medical records of children who sustained a TBI in order to identify those who could participate according to the inclusion and exclusion criteria. Then, the archivist communicated with the parents of the chosen children either by phone or mail to ask them if they were interested in receiving information about a research project in which their child could participate. The parents were also asked if they would consent to having their telephone number given to the study's investigator. If the parents accept, the investigator communicates with them to clearly explain the nature of the research project and its objectives. The parents were free to accept or to refuse their child's participation and they did not need to provide any explanation to justify their decision. If they agreed, the investigator asked them questions relating to the inclusion and exclusion criteria. Finally, the parents were invited to sign a consent form (see Appendix A) sent to them by mail.
For the children in the control group, school principals were contacted and asked to select a child who met matching criteria (sex, age and, whenever possible, socio- economic status). The researcher contacted the parents if they accepted to receive information. If they agreed to their child’s participation, they signed a consent form (see Appendix C) sent by mail. Children in the control group came from eight different schools in the province of Quebec, as well as from one Quebec City summer camp.
The child was met individually at his or her school, home, or at the rehabilitation centres where he or she was admitted for TBI. The child's parent, guardian, or teacher determined the most appropriate moment to meet. Before commencing the experimental procedure, the objectives and the procedure of the study were explained to the child by the investigator. If the child accepted to participate in the study, he or she was asked to sign an assent form (see Appendixes B and D).
Participants then completed a test of computer mouse manipulation, a reading test (the Test d’habiletés en lecture; Pépin & Loranger, 1999), and an aptitude test (the TAI-
enfants; Loranger & Pépin, 2001). All tests are computerized and were administered on a
portable computer. For the reading and aptitude tests, the child had to follow the instructions on the screen. The general instruction was: "Answer as well as you can while working rapidly". Each of the subtests has its specific instructions and is accompanied by one or many examples. The participant had to answer the practice items as if responding
to a real item. Then, the program indicated the correct answer. By completing these sample items, the child was familiarized with the tasks and the answer modality. The child could read the instructions for as long as he or she wished. Although he completed the tests independently, the experimenter stayed nearby offering assistance during the testing. If necessary, short breaks were provided.
Assessment lasted 45 minutes to one hour. The reading and aptitude tests were not administered in the same order for all participants in order to overcome sustained attention deficits that are frequently observed among children who suffered a TBI (Robin, Max, Stierwalt, Guenzer, & Lindgren, 1999). The characteristics of each test are explained in more details in the following section.
The Mouse manipulation test.
Motor speed is addressed in this test. This is a test of short duration (approximately 2 minutes) whereby the child must click as fast as he or she can on a four by four centimetre square that appears in different locations on the computer screen. Even if all of the participants had already used a computer mouse, a first practice series (30 trials) was conducted in order to familiarize them with the display qualities of the screen and to ensure that all children possessed the minimal abilities to complete the tests. The participants had to complete the same exercise (30 trials) a second time. During this second set, the computer recorded the speed of execution. Execution times were measured to verify if there was a difference in motor speed between the TBI and control groups.
Effect of information processing slowness 24
The Test d’habiletés en lecture (Pépin & Loranger, 1999).
This test, containing 40 items, includes three subtests: Decoding, Phonetic and
Comprehension. The decoding subtest evaluates the ability to discriminate letters and
series of letters that are often confusing for individuals with reading problems. This subtest requires the participants to judge whether a letter or a string of letters, shown at the bottom of the computer screen, include the letter or the string of letters appearing at the top of the screen. The participant had to click on a YES or NO icon with the mouse. The phonetic subtest assesses phonologic processing abilities. In this subtest, the participant had to determine whether a certain sound, which has been presented within a first word-stimulus, is found within a second word. The child had to provide an answer by clicking on a YES or NO icon. The comprehension subtest measures the ability to find meaning in a simple text. The participant had to read a text in which some words had been removed. Afterwards, he or she had to choose, from among four response choices, the word that best fills each blank. By involving multiple choices, this cloze technique permits the elimination of bias due to word finding problems or other aphasie symptoms that could have affected TBI performance if they have had to say or write the missing words.
In addition to a score of success or failure for each item, the Test d’habiletés en
lecture records execution time, in milliseconds, for each question. Within the context of
the third hypothesis, which proposes that a negative relationship exist between information processing speed, and the number of errors in the reading comprehension test, the execution time of the decoding and phonetic subtests were used to provide an indication of decoding and phonologic processing speed. Thus, only time was considered for those two subtests. The raw success scores on the comprehension subtest were used as a measure of performance in reading comprehension. Consequently, only the number of good responses was considered for the comprehension subtest. Even if the three subtests of the Test d’habiletés en lecture are positively related to each other, they assess abilities that are distinct and specific. Moreover, as previously mentioned, items are very homogeneous within each subtest. Thus, the specificity of the abilities measured by each
subtest justified tying together the execution speed for the decoding and phonetic subtests, and the number of errors of the comprehension subtest, which make up the elements of the third hypothesis.
The Test d’habiletés en lecture has good psychometric qualities. The Cronbach alpha coefficients range from .90 to .98 for each subtest, showing strong item homogeneity within each subtest. The scores for the three subtests are positively related to each other, with correlations varying from .68 to .79. Furthermore, each subtest is strongly related to the test's global result, with correlations ranging from .88 to .95. The three subtests are positively correlated with age and schooling (p < .001). These norms were derived from 1457 students in the province of Quebec.
The TAI-Enfants (Loranger & Pépin, 2001).
To evaluate speed of information processing, five subtests of the TAI-enfants were administered to the participants. The TAI-enfants is a computerized aptitude test that provides a score for speed of execution. This score is obtained by adding the latent periods of the six first items of the Analogy (Analogies), Arithmetic (Arithmétique),
Sequence (Sériation), Puzzle (Casse-tête) and Knowledge (Connaissances) subtests. Only
those subtests were administered to the children. The Analogy subtest requires children to find, between a set of pictures, the one that does not fit with the others. He or she had to indicate an answer by clicking on the picture with the mouse. In the Arithmetic subtest, the participant had to solve problems involving basic math operations. The Sequence subtest asks the child to find the logical continuation of a set of pictures, numbers, or letters according to a certain logical rule. The Puzzle subtest consists of a puzzle piece, a model depicting the puzzle, and a grid of answers. The task of the child is to assess the precise position of the puzzle piece from within the answer grid. Finally, the Knowledge subtest is a general knowledge multiple-choice questionnaire.
The Execution time variable of the TAI-Enfants has good psychometric qualities. The Cronbach alpha coefficient for this variable, calculated from the first six items of the
Effect of information processing slowness 26
subtests Analogy, Arithmetic, Sequence, Puzzle and Knowledge is .80. Correlations between raw scores on the subtests and the execution time score demonstrate that the score of execution time can be considered as an indication of performance. The normalization of the TAI-Enfants was conducted among 1631 children (Loranger & Pépin, 2001). Furthermore, the three conditions proposed by Anastasi (1988) to adequately measure speed of information processing are respected by the Execution time variable of the TAI-Enfants. Indeed, the first condition is that latency time must be calculated on successful items. Secondly, the response times used must be measured on items that are easy, that is, accurately performed by the majority of the participants. Finally, the items should be a part of a test that is administered individually.
Results
One-way analyses of variance (ANOVAs) were performed in order to compare performance and response times on the tests across groups. These analyses were done to test the first and second hypotheses, as well as any difference in motor speed between groups. Group (TBI or control) was the independent variable, while tests scores and response times were the dependent variables. Mean scores obtained by each group and univariate F ratios for each of the tests or subtests are listed in Table 2. A significance level of .05 was used. Each hypothesis and their associated results are presented in the following section.
INSERT TABLE 2 ABOUT HERE
Difference between groups for motor speed
There was no significant difference in motor speed between the performance of the TBI group and the control group as measured by the mouse manipulation test. Consequently, this variable was not used as a covariate, as intended.
Difference between groups for comprehension abilities
To test the first hypothesis, the number of correct responses in the comprehension subtest was compared between groups. TBI children performed significantly poorer than those of the control group on this subtest, F (1, 52) = 4,89, p = .031.
Differences between groups for the processing speed variable
The second hypothesis proposed that the TBI children would process information more slowly than the control group. Speed of general information processing was measured by the TAI-Enfants. The decoding and the phonetic subtests of the THAL measured decoding speed and phonetic speed, respectively. The mean response time of the TAI-Enfants was not significantly prolonged among TBI children compared to controls, and the performance of both groups was not significantly different in terms of correct answers. There was no significant difference between groups on phonological processing speed. However, TBI children performed significantly poorer than controls in terms of correct responses on the phonetic subtest, F (1, 52) = 4.63, p = .036. Finally, a significant difference was obtained between groups concerning decoding speed, F (1, 52) = 7.13, p = .01. The number of correct responses on the decoding subtest did not differ across groups.
Correlations between speed of information processing and reading comprehension abilities
To examine the relationship between speed of information processing and reading comprehension skills, Pearson correlation coefficients were calculated between the number of correct responses on the comprehension subtest on one hand, and the mean response times for the TAI-Enfants, as well as the decoding and phonetic subtests on the other. All participants were included to test this hypothesis. Large coefficients were obtained, varying from -.63 to -.83 as shown in Table 3.
Effect of information processing slowness 28
INSERT TABLE 3 ABOUT HERE
Effect of age at the time of TBI on reading comprehension abilities
The fourth hypothesis proposed that children who sustained their TBI when less than nine years of age will perform more poorly on the reading comprehension test than children who suffered their TBI at the age of nine or more. This hypothesis was tested on an exploratory basis because the number of participants in each group was small. In fact, only six children of the TBI group were more than nine years of age at the time of their TBI. Thus, six children of the TBI group who sustained their TBI after 9 years of age were matched to the younger TBI subjects according to their scores on the GCS and length of impaired consciousness. Thus, the TBI severity level frequencies were equivalent in both groups to ensure that differences in performance were due to the age of the children at the time of the injury and not to disproportional levels of TBI severity in one group compared to the other. The percentile scores, formed by the numbers of correct responses on the comprehension subtest with a bonus for the speed of response, were compared between both groups using the Mann-Whitney Test. The percentile scores provide the child’s classification within his or her age group by comparing his or her performance with the norms of the THAL. The percentile scores were used to overcome the fact that children of both groups were not matched for age. The performance of the younger group was not significantly different from that of the older group.
Correlations between early indices of severity of injury and performance in reading comprehension
Pearson correlation coefficients were calculated between early indices of severity of injury (length of impaired consciousness and GCS) and the performance of the TBI children in the reading comprehension subtest (number of correct responses and mean response time). Correlation coefficients were large between length of impaired consciousness and reading comprehension performance. They were smaller between GCS and reading comprehension performance. See Table 4 for more details.
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Gender differences
There was no significant difference between boys and girls in the control group with regard to their speed of information processing and accuracy in the TAI-enfants and the THAL. In the TBI group, the girls were slower than the boys on the TAI-enfants, F (1, 25) = 4.62, p = .041 and on the phonetic subtest, F (1, 25) = 5.38, p = .029. It is important to note that the TBI sustained by the girls were not significantly different in terms of severity from those sustained by the boys, as measured by the GCS and the length of lost of consciousness.
Discussion
This study aimed to shed light on reading comprehension abilities of TBI children and on the variables that could explain the reading comprehension deficits they experience. The results of the present study strongly suggest that TBI children present more reading comprehension difficulties than children who never experienced a TBI. Those results are consistent with those of other studies (Barnes & al., 1999; Ewing-Cobbs & al., 1998). Decoding speed appears to be of first importance to explain reading comprehension deficits. In fact, TBI children are slower than noninjured children in the first step of decoding: discrimination and identification of visual unit. Furthermore, a strong relationship is obtained between reading comprehension and decoding speed: the children decoding faster being better at understanding text. This finding fits with the Perfetti (1985) bottleneck hypothesis positing that decoding and comprehension processes are in competition to obtain the limited resources of the short-term memory. Thus, the faster the person reads the more resources she has to understand what she is reading. So, it maybe that TBI children, being slower in the discrimination and identification of letters, have less processing resources to integrate and comprehend text. It is interesting to note that TBI children are as efficient as control children in decoding; the only significant difference has to do with their speed.
Effect of information processing slowness 30
The opposite pattern of results was obtained concerning phonological awareness: TBI children were less proficient, without being slower than control children. This lack of competence has probably affected their reading comprehension skills. The ability to use phonological knowledge is important to decode new or less frequently seen words (Gillet, Kommet, & Billard, 2000). Due to their phonological deficits, the TBI children could have had some difficulties in decoding words of the passages they had to read and this could have led to a misunderstanding of the text.
In other respects, it is unlikely that the comprehension deficits could be explained by a deficiency in the capacity to make inferences because the reading comprehension subtest was very simple and only minimally implied this type of capacity. Furthermore, the TBI children have no less intellectual capacities than children who did not experienced a TBI as estimated by the TAI-Enfants. Thus, the reading comprehension deficits did not appear to be due to an intellectual deficiency. However, it is possible that mnemonic problems have had an impact on reading comprehension deficits. According to Stothard and Kulme (1996), while reading, information from text has to be held in memory to construct a meaningful sense of the text. Furthermore, children who experienced a TBI, typically have deficits in the functioning of mnemonic processes (Dennis, Wilkinson, Koski, & Humphreys, 1995). Another alternative explanation of the poor performance of the TBI children in the comprehension subtest could be that they don’t process contextual information as well as the control children. Context effects can speed word identification during reading. This way of viewing the poor readers’ performance is well explained by Stanovich (2000). Those hypothesises could be investigated in future research.
The results of the present study indicate that TBI children are slower in completing a reading comprehension task than children who did not experienced a TBI. The mean response time of TBI children was about 1.41 times slower than non-TBI children executing the same task. This finding is in accordance with their slowness in decoding abilities as well as with their phonological awareness deficits. In fact, the decoding slowness probably reduces reading rate. Moreover, phonological awareness difficulties,
by making word identification more difficult, increase the time taken to read and understand text.
Surprisingly, children who sustained a TBI did not present a general slowness of information processing as measured by the TAI-Enfants. This result contrasts with the fact that they present slowness in decoding and reading comprehension processes. This could be explained by the nature of the tasks. In fact, the TAI-Enfants does not involve many verbal materials. Only two subtests require the child to read and the reading demand is not important. Thus, the slowness of the TBI children seems specific to task involving verbal material (letters, words and sentences) and reading skills.
It could be argued that the diminished speed to decode and complete reading comprehension tasks is due to a problem of directing attention appropriately. However, if it were the case, the TBI children should have been slower than the control participants in all tests, not just in the decoding and comprehension subtest. Furthermore, the diminished speed does not seem to be due to a sustained attention deficit because the tests were not administered in the same order for all participants.
We were supposed to eliminate the impact of motor speed on the variables studied by using the time taken to complete the mouse manipulation test as a covariable. However, there was no significant difference between groups in regards to their motor speed. This result is inconsistent with those of other studies that found that severe childhood TBI slowed motor speed (Bawden, et al., 1985; Winogron, et al., 1984). However, in those studies, the interval between injury and testing was shorter than in the present study. Furthermore, the present study includes children who experienced a moderate TBI.
The fourth hypothesis, proposing that children who sustained their TBI before nine years of age would perform more poorly on the reading comprehension test than children who suffered their TBI afterwards, was not confirmed. This result is in contradiction with the one of Barnes and collaborators (1999). However, it is important to keep in mind that
Effect of Information processing slowness 32
this hypothesis was tested on an exploratory basis. In fact, the number of participants in each group was small, only six children of the TBI group being more than nine years of age at the time of their TBI. Thus, further studies including more participants should be undertaken in order to reach stronger conclusions.
The results of the present study demonstrated that the outcomes of TBI are not homogeneous. In fact, there is a relatively wide intragroup variability in the performance of the TBI children. This result is in accordance with the observations of Stuss and colleagues (1989). The reading comprehension outcomes may be influenced by many factors, like the severity of the injury, the area of the damages, the rehabilitation services obtained and the support of the family and the surrounding. Unfortunately, the present study did not verify all these possibilities. However, it allows us to realize that the length of impaired consciousness is strongly associated with the capacity to understand a text and the rapidity to read it. Thus, the children who had the longest length of consciousness had the highest probability to experience reading comprehension deficits or slowness in reading. A moderate relationship was obtained between GCS and speed of completion of the reading comprehension task. However, the association was small between the GCS and the reading comprehension performance. This finding is partially in agreement with the one of Barnes and colleagues (1999) who found that GCS were not related to reading comprehension capacities. Thus, it seems that the length of impaired consciousness is the early indicator of injury severity the most strongly related to the reading comprehension outcome.
The deficits obtained in the present study minimize perhaps the real problems TBI children encounter in the academic environment. In fact, while participating to the present study, TBI children were in an ideal situation to perform at their best. They were alone with the experimenter, they could ask the questions they wanted and be provided with answers immediately. Moreover, the environment was quiet and free from distractions. The situation is quite different in a classroom. In the study of Ewing-Cobbs and collaborators (1998), the scores in achievement tests, including a reading comprehension test, were not representative of the factual outcomes of TBI children.
