Color and Object Naming Speed Predicts Future Risk for Dyslexia
Wednesday, January 20, 2010
An important goal for any developmental disorder research is early detection. The earlier the detection, the earlier we can start intervention and treatment. Dyslexia is tricky though. It’s a reading disorder, and by definition cannot be diagnosed until reading instruction begins. However, we can still look for signs that predict future risk for dyslexia.
One predictor of future dyslexia is rapid automatized naming (RAN) speed. A RAN test consists of naming an array of objects, colors, letters, or symbols as quickly as possible. It makes sense that letter and symbol naming speed (also called alphanumeric RAN) might predict reading skill. Surprisingly however, speed at naming pictures of objects and color patches also predicts future reading skill. Lervag and Hulme (Psychological Science 2009) studied this in a longitudinal study of Norwegian schoolchildren.
The idea was to test children before they learn to read and look for test results that predicted future reading skill. Formal reading instruction in Norway begins in second grade. Therefore, Lervag and colleagues conducted several tests on first graders. These tests included RAN and phoneme awareness (tasks like picking a word that begins with a certain sound). They then retested the students in second, third and fourth grade on these skills as well as reading fluency. They found that performance on nonalphanumeric RAN in first grade predicts phoneme awareness and reading fluency later on.
Lervag and colleagues investigated this finding in further detail by separating the RAN response times into articulation times and pause times between words. They found that the pause times were a much better predictor of future reading performance than articulation times. It should be noted though, that articulation times were much less variable than pause times, with a standard deviation of around 4.5 ms rather than about 16 ms.
These are pretty interesting results, and it raises the obvious question -- what is it about rapid color and object naming that predicts future reading skill? I can think of several possibilities.
1. Lervag suggests that reading may be tapping into the same pathways used for object recognition and naming. Remember the mirror invariance paper from last week that suggested the visual word form area might be involved both in word and object recognition? It could be that both reading and object naming are served by the same brain areas.
Both reading and rapid naming involve seeing an object, retrieving its phonological representation, and outputting the phonology via motor routines. Perhaps performance in RAN reflects the strength of the connections between visual, phonological, and speech areas.
2. Attentional focusing could be another factor. Rapid automatized naming requires directing visual attention from one object to the next in a controlled manner, and reading requires the same skill. Perhaps a deficit in attentional focus could be the underlying factor.
3. An even lower level explanation would be visual motor control. Both RAN and reading require controlled eye movements from one item to the next. Deficits in motor control have been reported in dyslexia, but I don’t know of any reported eye movement deficits. If anyone knows more about this, do let me know.
What do you think is the connection between RAN and dyslexia?
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10 comments:
Several years ago, I defragmented my dyslexic daughter's computer. It ran much faster. This caused my daughter to says she feel like her brain needs to be defragmented.
This suggests the word-form area is implicated.
From a practical or classroom point of view, having a valid screening test for risk of later reading difficulties would be wonderful--normed to include children as young as 48 months.
Liz -- maybe you should have had the computer do some RAN tests :-)
Thank you, Livia for bringing up this important topic in reading research. My comment focuses more on uses of the RAN. Many clinicians and neuropsychologists make the mistake of conceptulasing the RAN as an outcome measure. This means they expect to see change after intervention. In some children that is the case, but I think that has more to do with the inherent unreliability of testing children (my opinion). It is more accurate to conceive of the RAN as more like an intelligence test than as an outcome measure. It seems to describe a default behavior of the brains of slow namers when confronted with this type of visual stimuli. If that is true than Livia's explanation number one would seem to make a great of sense. It would be interesting to find out if you could devise a naming task that requires the subject to name some kind of stimuli that relies on other parts of the visual cortex.
Anonymous -- that's a really interesting idea. Scene processing regions are further away from word processing regions, so it'd be interesting to see if scene naming is less good of a predictor.
Boy, it's a good thing I posted anonymously. Look at all those typos!But yes, that is what I was getting at. Are dyslexics impaired in their ability to connect the regions of the brain important to reading, but not impaired when the task demands connecting other regions of the brain?
Your first possible explanation has persuaded me the most so far (especially taking into consideration the mirror invariance paper). Regarding your second possible explanation, would it be helpful to follow up with the subjects years after to try to theorize attention deficit effects on this study? For example, if this data were to be collected years later, the study results of subjects later diagnosed with an attention deficit disorder could be compared with the study results of subjects later showing no attention deficit disorder symptoms.
this are some interesting comments on the correlation between rapid automatized naming and identifying dyslexia. Do you have a reference to this article? (The only articles I found were the articles written by scientists in the 1990's.) I was looking up other articles that discussed this topic... there was one article discussing some of the work done by a Tufts University Psychology Maryanne Wolf, PhD.
The article quotes that "In fact, rapid-naming tasks appear to measure something separate from phoneme awareness, says Wolf. The measure itself correlates only weakly with phoneme awareness. Also, Wolf and others find that children with dyslexia can have problems with both phoneme-awareness tasks and rapid-naming tasks or with just one or the other task, indicating the two are mutually exclusive."
Its interesting because she isn't arguing that the correlation between RAN and phenome awareness isn't important, but I think the article discusses that this reveals only the "tip of the iceberg" and there are many other cognitive processes not accounted for.
Yet, many neuroscientists do research that do support the idea that RAN can help with identifying dyslexia at an early stage, so I guess perhaps its a matter of seeing what the research results produce.
Here is a great article by George K. Georgiou, Rapid naming speed and reading across languages that vary in orthographic consistency that summarizes a great deal of research on naming speed as a predictor and as a diagnostic tool in languages other than English. Heinz Wimmer is another name to look up regarding cross-linguistic research on naming speed. Naming speed research in other languages is particularly powerful, because phonemic awareness deficits have less impact on children's outcomes in languages with transparent orthographies. The result are reading deficits almost exclusively in fluency (and then of course comprehension).
I wonder if there is a connection to Vygotsky's theory of labeling items with language in imaginative, cooperative play.
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