Reading is not an individual achievement
Reading is not a single achievement, but comes about through the coordination of numerous different achievements. The neuronal networks that mediate these services are not located at an anatomically defined location in the brain, but are scattered throughout the brain. Each of the brain functions necessary for reading can be diminished, while all other functions are preserved. If one or more of these services is impaired, reading disorder or reading impairment may occur. Whether one speaks of a reading disorder or a reading disorder depends on the degree to which reading performance is reduced. The reduction of brain function necessary for reading can be caused by a non-optimal development or by an acquired dysfunction of the neuronal network concerned. However, psychological factors such as reduced attention, lack of motivation, fear, defensive posture and other psychological problems can also lead to certain brain functions not being sufficiently exploited even though these brain functions are completely normal and undisturbed. If there is a lack of motivation to read, for example, the neural networks necessary for reading are not sufficiently activated. However, these networks could be sufficiently activated if there were sufficient motivation. Even in children with normally developed neuronal networks, an incorrectly learned reading strategy can lead to reduced reading performance. If there is no developmental or acquired dysfunction of at least one of the neuronal networks necessary for reading, one is more likely to speak of a reading weakness than a reading disorder.
Evaluation of reading performance
Traditionally, reading performance is related to measured intelligence. This is referred to as a reading disorder if the reading performance measured in a reading test is at least 2 standard deviations less than the result of an intelligence test. According to a decree of the Free State of Bavaria, reading weakness occurs when an intelligence quotient of at least 85 is reached, but the reading performance measured in the reading test is less than 12 T-value points below the intelligence quotient. Such a differentiation, however, is the result of statistical arbitrariness and has no psychological or neurobiological basis. How pronounced a reduced reading performance is depends on the degree of functional impairment of one or more neuronal networks, on the extent of psychological problems or on an unsuitable reading strategy. A mere statistical delimitation of a reading disorder and reading weakness overlooks the different causes to which the reading problem is attributable and the different therapeutic steps that are appropriate. Since the reading disorder as well as the reading weakness can have completely different causes, it is not sufficient for the diagnosis of a reading disorder or reading weakness only to state the existence of a reading performance reduced in comparison to the age norm. Instead, the respective causes of the reading disorder must be identified. Consequently, there is not a single universal reading therapy. This must be based on the respective causes of the reading disorder or reading weakness. In the case of a reading disorder, the respective diminished brain performance must be identified and therapeutically considered. At the University of Munich, we have developed PC-supported procedures that make it possible to diagnose brain performance whose reduction is the cause of a reading disorder in a child, adolescent or adult and to treat the causes in a related manner.
Fixation phases too short
A frequent cause of reading disorders are too short fixation phases. Whether a fixation phase is too short depends on how long a person has to fix a word or a word segment, i.e. has to look at a word so that this word is imaged on the retina in the area of sharpest vision. These fixation phases required for recognition are not the same for all persons. Good readers at the age of 7 are often able to recognize pseudowords of a length of 6 letters if they are offered for less than 100 milliseconds, i.e. the fixation phase lasts only 100 milliseconds. Children with reading problems often need 500 milliseconds to recognize 3 or only 2 letters. Some children cannot recognize more letters even during longer fixation times. When reading a normal text, the brain must know how long a child has to look at a word, i.e. how long the word has to be imaged, i.e. fixed, in the area of sharpest vision, the fovea, so that it can be recognized reliably. One type of reading disorder is caused by the fact that children do not look at a word long enough (do not fix the word long enough). Their fixation time is too short, i.e. it is shorter than the fixation time required to recognize the word or word segment in question. This also shows that, in contrast to a common practice, it does not make sense to specify standard values for the fixation time. If you need only 100 milliseconds to recognize a word, you need only 100 milliseconds to look at the word. A reader who requires a presentation time of 400 milliseconds to recognize a word must also look at the word for at least 400 milliseconds. Reading errors only occur if the required fixation time is not observed (Werth 2006, 2007, 2018). As our research shows, however, it is not only letters at the beginning or end of a word that are overlooked. The unrecognized letters can occupy different positions within a word.
Reduced ability to recognize simultaneously
Within a fixation phase, however, not one letter after the other is recognized, but the letters of the word or word segment that a person tries to read are recognized approximately simultaneously. Neuropsychological investigations have shown that the simultaneous recognition of several objects (in this case, letters) is a brain performance of its own, which is more or less well developed independently of other brain performances. This performance is also usually reduced in children with a reading disorder. Reading errors occur when children try to recognize more letters simultaneously than they can recognize. The unrecognised letters are then guessed.
Reduced attention field
Although the ability to recognise simultaneously is normal, the simultaneous recognition of several letters may be limited due to a narrowing of the attention field. The attention field is the area of the visual field into which attention is directed. If, for example, attention is directed to the centre of the visual field in order to look closely at an object appearing there, the extent of the attention field is reduced (Werth 2012). As a result, stimuli appearing outside the centre of the visual field are more likely to be overlooked. The size of the attention field also varies during reading depending on the degree to which recognition of certain text segments demands attention (Rayner 1986; Henderson and Ferreira 1990). If the simultaneous recognition of letters is difficult for a reader, he has to focus all his attention on e.g. 3 letters in the middle of the currently fixed word. This has the consequence that the attention in the surrounding visual field decreases: The attention field decreases. The recognition of letters within a word is particularly susceptible to reduced attentiveness, as these letters are more difficult to recognise than single letters due to so-called lateral masking. A reduced attention field alone is already sufficient for the development of a reading disorder.
Unadjusted size of gaze jumps
As already described, a word or word segment can only be correctly recognized if the gaze is directed at it in such a way that it is imaged in the area of sharpest vision, the foveal area of the retina. The reason for this is that the visual acuity is only sufficient in this small area in the centre of the visual field to be able to read the text of a daily newspaper or a book. When looking at a book page, therefore, only the small section of the page that is imaged in the fovea area in the centre of our retina can be seen clearly. In order to be able to read the entire text, the adjoining text sections must therefore be shifted one after the other into the sharply seeing centre of the visual field. This is done by saccades (Rayner et al. 1996). For example, if you want to read the sentence “Peter worked yesterday evening”, you must first look at the first word Peter. The gaze is directed to the middle of the word, i.e. to the t (Underwood et al. 1990). If, while reading a text, a word or a word segment was recognized within a fixation phase, a jump to the next word or word segment occurs. This leap must be large enough that the word segment to be read after the leap follows the word segment read before the leap (Morris et al. 1990). This is another cause of reading disorders, as some children make too large an eye leap. Let us assume that a word segment with a size of 5 letters could be read with the gaze directed to the middle letter. Now there is a leap over 7 letters to the next word segment. Again the child can recognize 2 letters to the left and 2 letters to the right of the fixed middle letter of the word segment to be read in addition to the fixed letter. If such large eye jumps are performed, 2 letters are overlooked between the two word segments. Children often supplement the missing letters. Since the additions are often wrong, the children read again and again what is not in the text. The size of the eye jumps must therefore be aligned with the size of the word segments that a child can read and must not be aligned with the size of the eye jumps of normal readers as a given standard. The question of whether gaze jumps deviating from the norm can cause a reading disorder when reading is still a controversial one today (Rayner 1978; Pavlidis 1985; Conners 1990; Biscaldi et al. 2000; Fischer and Hartnegg 2000). It has been argued that the irregular eye movements frequently found in subjects with a “reading disorder” can also occur in good readers and that poor readers can also show normal eye movements. In a new study we were able to show that reading disorders are not caused by abnormal eye movements. The cause was a reduction in the fixation phase often accompanied by irregular eye movements and an incomplete fixation of word segments to be read.
Reduced performance of memory and retrieval of sound sequences
If word segments to be read have been correctly analyzed by the visual system, the seen word segments must be associated with the correct sound sequences. This ability can be reduced for several reasons. One form of interference is that the path from structures of the visual cortex to brain structures, in which the associated sound sequences are stored, is impaired in its function. Another cause is that the memory for sound sequences is reached without interference. However, the ability of memory to store sound sequences can be impaired. Typical of this is the frequently observed confusion of letters, such as b and d, p and q, or m and n. These children cannot remember which sound is associated with the d and which with the b, which with the p and which with the q, which with the m and which with the n. Other children can name these letters correctly if they have enough time to look for the right sounds in their memory. However, if these letters appear within a text to be read, they will always be read incorrectly. The reason for this is often that some children need more time than others to retrieve the sound or sequence of sounds belonging to a letter or sequence of letters. Attempting to read a text fluently does not give some children the time they need to retrieve it, and errors occur. Such errors can easily be avoided by extending the retrieval time. For example, if the PC gives a certain time interval after a word segment appears a signal that the child must not start pronouncing the word segment before the signal sounds, it is easy to vary this time interval to determine how long the child’s retrieval time must be. With many children, the error rate drops drastically as soon as there is sufficient retrieval time available. The error rate immediately returns to the initial level if the retrieval time is shortened beyond a certain limit. If it is a reproducible effect, the too short retrieval time is a sufficient condition for the occurrence of the reading disorder and can logically be regarded correctly as its cause.
Reduced retention of read word segments and lack of shared attention
Reading does not only mean connecting successive word segments or words with sound sequences. The word segments that are seen during the fixation phases, which are separated by leaps and bounds, must be stored in memory, combined into sentences and given a meaning. This performance can also be disturbed in many ways. For example, the ability to store word segments seen one after the other in memory and to combine them into words and sentences may be reduced. The reader can then read out a sentence correctly without understanding the content of what has been read. Children with such a reading disorder already face problems when reading simple texts, which normal readers only face when reading incomprehensible or difficult to understand texts.
Overstrain of shared attention services
Not always when children read a text but do not understand the content of what they have read, such a reduction in memory performance must be the cause. Often the reason for the lack of understanding is that the reading process itself causes so much trouble for the children and demands all their attention that they can no longer pay attention to the content of the text. This means that children find it difficult to focus their attention on remembering segments of words they have read, putting them together into meaningful words and sentences, and giving them meaning. Not infrequently, the capacity to understand simple texts is sufficient. The difficulties, however, become apparent when children are asked to solve text problems in mathematics. Now that every word of the text must be understood, reading a text task requires attention to the content of the text. It is then not possible to focus part of the attention on the content because the reading process itself requires too much attention.
Reading disorders and reading weaknesses have many causes
In addition to the above-mentioned causes of reading disorders, there are other performance deficits which can be causes of reading disorders or reading difficulties. In addition to severe visual impairment, hearing impairment and speech impairment, the following 14 disorders caused a reading disorder in our controlled studies (Werth 2007, 2018, Klische 2007):
- The word or word segment to be read is not fixed in the right place.
- The word or word segment to be read is fixed too short.
- The individual letters of the word or word segment to be read are recognized, but the child takes too long or is unable to retrieve the sound sequence belonging to the letter sequence.
- Only small word segments can be recognized because the attention field cannot be extended further. However, the child tries to read larger word segments.
- Only small word segments can be read because the ability to recognize several letters simultaneously is too weak. However, the attention field can be sufficiently extended.
- When reading, too large an eye leaps are performed. This often overlooks letters, word segments or whole words. The child often guesses the word to be read because it has only partially recognized the word or not recognized it at all.
- The impaired visual performance during the eye jump recovers after the eye jump too slowly to read the now fixed word or word segment.
- The child cannot concentrate his or her attention enough on reading a word or word segment because he or she is distracted by the text around the word or word segment to be read.
- The child is forced to look again and again at words or word segments that have already been read correctly in order to check whether they have read correctly. This prevents fluent reading.
- Although the child can read, he or she cannot grasp the content of what he or she has read, as he or she must focus all attention on the reading process and therefore cannot pay any attention to the content.
- The child can read, but cannot remember the meaning of words read long enough to grasp the content of a text. This poor performance is caused by a reduced memory line for read words.
- Words read cannot be associated with a meaning or the meaning cannot be retrieved from memory quickly enough. This almost exclusively affects children who read a text that is not written in their mother tongue.
- Pseudowords that can be pronounced can be read correctly. However, words in an existing language are often misread because the child cannot recall the pronunciation rules from memory quickly enough and/or apply them to the pronunciation of the seen word. This almost exclusively affects children who read a text that is not written in their mother tongue.
- Words are correctly analyzed by the visual system, the sounds of the individual letters are correctly recalled from memory, the word can be correctly pronounced, but the sound sequence of the entire word cannot be correctly formed if the word is visually offered.
As already mentioned, psychological problems, such as school anxiety or lack of motivation, can also cause reading problems, which we then call “reading difficulties”. But this is not another category of causes. It is the same neuronal structures that show a reduced performance when reading. The difference is that the reading disorder is a developmental or acquired functional impairment of the neural networks necessary for reading. In the case of a reading disorder, psychological problems lead to the fact that the performance of normally functioning neural networks is not exhausted. For example, lack of motivation to read typically leads to very short fixation times (cf. cause 2), to a small field of attention (cause 4) and to large jumps in vision (cause 6). If the fixation times are extended, the word segments to be read are reduced and the gaze jumps are reduced, it is usually possible to read correctly without increasing motivation. On the other hand, an increase in motivation to read is already sufficient so that more letters are recognized at the same time, the attention field is enlarged and the fixation times and gaze jumps are adjusted. This is done by activating the neuronal structures necessary for reading more strongly and thereby increasing their performance.
Reading difficulties often have the following causes:
- The word or word segment to be read is not fixed in the right place.
- The word or word segment to be read is fixed too short.
- Only small word segments can be recognized, because the attention field is not extended further, although it could be sufficiently extended with appropriate effort. However, the child tries to read larger word segments.
- Only small word segments can be read, because the ability to recognize several letters simultaneously is not exhausted by too little effort. However, the attention field can be sufficiently extended.
- When reading, too large an eye leaps are carried out. This often causes letters, word segments or entire words to be overlooked. The child often guesses the word to be read because it has only partially recognized the word or not recognized it at all.
- Although the child can read, it cannot grasp the content of what it has read because it pays too little attention to the content.
Since reading disorders as well as reading difficulties can have different causes, and these causes in the case of reading disorders are based on functional weaknesses or functional failures in different brain structures, in the case of reading difficulties are based on a lack of activation of the respective brain structures, it is not possible to speak of “dyslexia” or “dyslexia” or only of reading difficulties as such. Instead, each child should be differentiated between reading disorders and reading difficulties of various causes.
The above should also have made it clear that the criterion based on the measured intelligence as to whether there is a reading disorder, a reading weakness or dyslexia in general is completely unsuitable. If a student with an intelligence quotient of 130 jumps in his gaze, if he fixes the word or word segment to be read too short, if his ability to recognize several letters at the same time is reduced, etc., his reading ability is reduced in the same way and by the same causes as with a peer who has a reduced reading ability for the same causes, but only has an intelligence quotient of 85 or 70. Whether there is a reading disorder or a reading weakness is independent of other performance measured by the intelligence quotient. This is based on the fundamental insight of neuropsychology that certain performance can be selectively reduced, while the remaining performance spectrum is completely normal or even exceeds the norm.
Diagnostics of causes and causes of directed therapy
The causes of reading disorders can be determined by repeatedly eliminating possible causes of the reading disorder one after the other and by investigating whether the reading disorder then immediately disappears. Conditions are switched off by offering the word segments, words or sentences to be read on a monitor under such conditions that certain possible causes of reading disorders can no longer occur (Werth 2007, Werth et al. 2001-2012). Two forms of therapy can be distinguished: a therapy to increase limited performance and a therapy to compensate for limited performance. The therapy for the improvement of a limited performance consists in the fact that the reduced ability of a child, e.g. the ability to recognize only 3 letters at the same time, is tried to improve by a systematic training so far that more than 3 letters can be recognized simultaneously. Such a therapy, however, is lengthy and usually reaches biological limits. Compensatory therapy, on the other hand, involves the child learning a reading strategy with which he or she can read without error even though he or she can only recognize 3 letters at the same time. This compensatory therapy led directly to success if the children followed the reading strategy suitable for them (Werth 2007; Klische 2007, Werth 2018). In this therapy, the PC indicates where the child has to look, how long it has to fix each time, how many letters it has to recognize simultaneously, when it has to start pronouncing, how big the jumps in the gaze should be, etc. The PC also indicates how long the child has to look at the computer. Since not all children have to fix the same length of time, not all can recognize the same number of letters simultaneously, not all need the same length of time before they can start pronouncing, the reading strategy must be adapted to each child. If the reading strategy is mastered on the PC, the child learns to transfer it to reading a normal text. In the case of reading difficulties, it is often sufficient to overcome the fear of school or to increase motivation so that the fixation times are extended, more letters are recognized at the same time, the jumps in gaze are adjusted and the retrieval from memory is improved. Two previous independent studies have shown that reading errors can be reduced by about two-thirds in a single hour. The two control groups in which the causes of the “reading disorder” persisted, however, did not reduce their number of errors (Werth 2006, 2007, Klische 2007). A new study confirmed these results. This study showed that the improvement in reading performance was not a therapeutic exercise effect independent of compensation, but the result of compensation of causes independent of reading exercise. Individual case analyses that go beyond the comparison of the therapy and control groups show how an immediate improvement in reading performance is achieved through the interaction of eye movement control, fixation times, simultaneous recognition, the structure of the attention field and the retrieval of a sequence of sounds belonging to a letter sequence. If there is only one reading weakness, this can often be eliminated by eliminating the psychological factors that led to this reading weakness.
- Biscaldi M, Fischer B, Hartnegg K, Voluntary saccadic control in dyslexia. Perception 29 (2000) 509-521.
- Connors CK, Dyslexia and the neuropsychology of attention. In: Pavlidis GT (Hrsg.)
- Perspectives on Dyslexia Vol I. Neurology and Genetics. John Wiley, Chichester et al. 1990, S. 163-195.
- Fischer B, Hartnegg K: Effects of visual training on saccade control in dyslexia. Perception 29 (2000) 531-542.
- Henderson JM und Ferreira F, Effects of foveal processing difficulty on the perceptual span in reading: implications for attention and eye movements control. J Exp Psychol Learn Mem Cogn 16 (1990) 417-429.
- Klische A. Leseschwächen gezielt beheben. – Individuelle Diagnose und Therapie mit dem Programm celeco. Tectum, Marburg 2007.
- Morris RK, Rayner K, Pollatsek A: Eye movement guidance in reading: the role of parafoveal letter and space information. Journal of Experimental Psychology Human Perception and Performance 16 (1990) 228-281.
- Pavlidis GT. Do eye movements hold the key to dyslexia? Neuropsychologia 19 (1981) 57-64.
- Pavlidis GT. Eye movements in dyslexia: Their diagnostic significance. Journal of Learning Disabilities 18 (1985) 42-50.
- Rayner K. Eye movements in reading and information processing. Psychological Review 85 (1978) 618-660.
- Rayner K: Eye movements and the perceptual span in beginning and skilled readers. J Exp Child Psychol 41 (1986) 211-236).
- Rayner K, Sereno SC, Raney GE: Eye movement control in reading: a comparison of two types of models. Journal of Experimental Psychology Human Perception and Performance 22 (1996) 1188-1200.
- Werth R. Über die Möglichkeit, die Ursachen der Legasthenie zu erkennen und zu therapieren. Erziehung und Unterricht 9-10 (2006) 856-865.
- Werth R. Legasthenie und andere Lesestörungen – wie man sie erkennt und behandelt (3. Auflage). CH Beck, München 2007.
- Werth R. Die Natur des Bewusstseins – Wie Wahrnehmung und der freie Wille im Gehirn entstehen. CH Beck, München 2010.
- Werth R, Barner T, Weser T. Richtig lesen lernen – Diagnose und Therapie der Legasthenie und anderer Lesestörungen. Celeco, München 2001-2012.
- Werth R. Die vielen Facetten der Aufmerksamkeit. Spektrum der Wissenschaft 2 (2012) 36-41.
- Werth, R. (2018). Rapid improvement of reading performance in children with dyslexia by altering the reading strategy: a novel approach to diagnoses und therapy of reading deficiencies. Restorative Neurology and Neuroscience, 36, 679-691. DOI 10.3233/RNN-180829