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Reading: The Brain’s Challenge: Processing Stutters – Processing Speed

Have you ever experienced a jerky video because your internet connection was too slow or your DVD was scratched? Has your mouse ever seemed to freeze when your computer was running too many apps? These are examples of stutters in the flow of your experience caused by stutters in the processing of your technology (internet, DVD, computer, etc.). They’re the result of your ‘processor’ not keeping up with the flow of your attention*. It’s the same for struggling readers. The hesitations, starts, and stops you hear in the voices of struggling readers are caused by their brain’s ‘processing’ not producing words fast enough to keep up with their attention span and articulation stream and failing to keep up with the flow of their attention as well The difference is, for struggling readers, the technology at issue isn’t made of microchips it’s made of neuro-circuits in their brains.

There are many factors* that can cause the brain’s processing to stutter when reading and in future posts we will address most if not all of them. In this post we begin our exploration of the bottlenecks – the causes of processing stutters – to reading fluency by looking at ‘processing speed’.

To illustrate the critical role of processing speed in reading, imagine how frustrating it would be to run the apps you use today on one of your first computers:


The fluidity of your experience watching this online video is like the fluidity of your experience reading these words. The flowing coherency of your experience depends on whether the processing machinery stays up with the pace of your attention. Trying to play this video with a poor internet connection or too slow a machine will result in a frustrating experience that you will soon want to quit. The same is true for most of the kids struggling with reading. Their machinery just isn’t up to projecting a fluid stream.

Why is processing speed important? Because our brains need information to flow at certain rates for the information to make sense to us. Just as we can only see certain frequencies of light and hear certain frequencies of sound, our minds can only make meaning out of information that flows within certain ranges of speed. For our purposes in this post, the most relevant example of this is the speed of language. Our minds can only understand spoken language when the word-sounds are flowing at certain rates. If the rate is too fast or too slow we can’t recognize them – they become unintelligible.


Spoken language has a narrow temporal profile. If language flows to fast or slow (or our brains process language too slow) it becomes harder for us to recognize words.

Our brains produce and recognize words by processing the sounds inside of words (phonemes). According to research into human interaction speeds, a commonly comfortable pace for listening is around 150-160 words per minute. That’s 2.5 words per second and, obviously, the phonemes are flying by even faster:

How fast can you say, “He stuck in his thumb, and pulled out a plum”?  That takes me about 3 seconds to say normally.  That sentence contains 28 phonemes.  That means I am saying over 9 phonemes every second! -Dr. Bruce Murray

But even more important than any averaged rate of phonemes per second, our brains have to be able differentiate (unconsciously distinguish and recognize) phonemes at the rate they actually occur in typical speaking and listening:


Human speech moves so fast that the differences in sound that make words recognizably different routinely occur in less than a tenth of a second. In other words in order to make sense of out speech our brain is paying attention to sound changes happening in small fractions of a second.

As the video illustrates, the changes in sound that our brains need to track in order to distinguish words can occur in less than 50 thousands (half of a tenth) of a second. Learning to speak and listen to language therefore depends on our brain’s ability to recognize variations in the sound stream at that rate.  This is important because the brain processes involved in reading must generate an internally heard simulation of words or spoken stream of words that is moving at speeds roughly approximating the rate our minds are accustomed to with spoken language (see video: “Profiles of Intelligibility” above). Therein lies the ‘bottleneck’. Why? Because if the code isn’t being processed into recognized words fast enough all the other parts of our language comprehension processing stutter and break down:


Human speech moves so fast that the differences in sound that make words recognizably different routinely occur in less than a tenth. In other words in order to make sense of out speech our brain is paying attention to sound changes happening in small fractions of a second.

Reading is an artificially inseminated language experience.  The brain-machinery involved must produce a simulated stream of language that is, at least initially*, moving at a pace very similar to ‘real’ language if it is to be comprehended. In other words, in order to comprehend the words we are reading, the parts of our brain that are constructing the words must keep the parts of our brain involved in comprehension processing ‘fed’ at a rate at least roughly approximating that of natural language.  If the stream of simulated words assembled by ‘decoding’ processes falls below a certain threshold of speed the stream of comprehension will ‘stutter’ just like an online video will stutter when your connection is too slow or your computer is overtaxed.

What’s taking up so much processing time? See: “The Brain’s Challenge: Disambiguation

*Attention: The rate you’ve learned to expect. People used to take coffee breaks for computational tasks that take no discernible time to us today. If you think you are watching a slideshow that changes every 5 seconds your attentional expectation is different than when watching a video.

*Many Factors:  Insufficient phonemic differentiation – vocabulary deficits – working memory limitations – low frustration tolerance – emotional distraction (particularly shame) – attention deficit disorders – poor letter recognition – classic innate dyslexia – maladaptive cognitive schema.

*Initial Speed: though good readers progress to read faster than sound they don’t start off that way.

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4 Responses to Reading: The Brain’s Challenge: Processing Stutters – Processing Speed

  1. Barbara Todd July 7, 2012 at 11:22 pm #

    Excellent analogy and description of the importance of fluency.  I will share this with teachers.  Thanks.


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