Reading speed adapts to the tools of perception, says S.Ananthanarayanan.

It is pointless to speak faster than the listener can understand. This, however, is not true of writing, as the written word is static. On what does how fast we read depend?

This and other questions were looked into by a team of researchers in communication, perception and neuroscience. Benjamin Gagl, Klara Gregorova , Julius Golch, Stefan Hawelka , Jona Sassenhagen, Alessandro Tavano, David Poeppel and Christian J. Fiebach, from Goethe University, the Centre for Individual Development and Adaptive Education for Children at Risk, Max Planck Institute for Empirical Aesthetics, Ernst Struengmann Institute for Neuroscience, Max Planck-NYU Centre for Language, Music and Emotion, all in Frankfurt, Department of Linguistics, University of Vienna, Department of Psychology, New York University and the Centre for Cognitive Neuroscience, University of Salzburg, describe their studies in a paper in the journal, Nature Behaviour.

Speech, and oral communications, of course, came before writing and reading. And there has been much research into the modalities of speech. While one aspect of the study has been the form and structure of words, recent studies have been in the rhythm, or the time-structure of the sounds that constitute the words. “….specifically, regularities in the envelope of the acoustic signal that correlate with syllabic information and that play a central role in production and perception processes,” says a reference cited in the paper. It is possible, another reference says, that brain adapted an existing mechanism to process and make sense out of sound patterns, when animal sound signals grew into speech as a form of complex, human communication.

Spoken languages, the paper says, consists of rhythmic peaks of loudness, which mark the constituents, the phonemes, the distinct units of sound that make up the language. And, over all languages, these peaks appear 4.3 to 5.5 times a second, the paper says. And this, the paper says, corresponds to the time, about one fifth of a second, that the brain is found to take to process a unit of information conveyed by sound. That the rate at which the brain has adapted to process information should be the rate at which signals have come to be produced while speaking appears to be a reasonable way in which speech and perception have developed.

Next comes the development of writing and reading. Writing is a visual means of recording meaning, using, the same units, the words, that are used in speech. And reading is to recover, from the visual representation, the words that were to be conveyed. Interestingly, the paper says, the time for which the eye, while it scans written matter, pauses, or fixates, to perceive units in the writing, is also the same, approximately one fifth of a second. This is in the case of writing systems that use alphabets, and a little more, a fourth of a second, in the case of languages that use characters, like Chinese.

There are now methods to detect and measure, with fine resolution, the movements of the eye in the course of reading. These have been used extensively to study how the eye takes in units of writing, like words, and to see how reading is influenced by factors like word length, frequency or predictability. In the present study, the authors of the paper examine how eye movements can be related to the time spent on language components. This could help understand whether reading is related to the way spoken language is processed, and whether how the eyes scan writing is different from the way they scan other kinds of visual matter, the paper says.

The method used was that fifty volunteers were got to read a collection of sentences, and while they read, the movements of their right eye was tracked, every thousandth of a second. What was measured was the length of the pauses between the shifts of gaze, as the reader went though the written matter. These pauses were when the eyes focused on the image and the time for perception, as opposed to the time between the pauses. And the result was that the pauses lasted, on the average, 197 milliseconds, or almost a fifth of a second, just like the rhythmic peaks when the text is spoken

And, to validate the finding, results of 124 studies, using 14 different languages were analysed. And again, with groups non-native and native German speakers. The results showed consistently, that written text is sampled, when read, at the same rate as in spoken language, and the rate, for reading, the frequency of pauses in scanning is not more than about 5 pauses a second. Also, that this rate can vary according to the complexity of the written script. (This however, is in the case of readers with lower levels of reading skills, or non-native readers. This is because highly skilled readers scan sets of words, or phrases, while reading.)

What the work show, is hence that during reading, our eyes ‘sample’ written text at the same rate in which speech is produced and perceived. This suggests that the time structure the brain follows in retrieving information is the same, both from written matter and from speech. A possible explanation, the paper says, is that the brain has evolved to process signals at a rate that has been determined by constraints of the vocal chords, and hence the rhythms found in speech. With the arrival of the written medium, the brain imposes on the eyes a pace of movements that matches the rate at which the brain can process information.

“Eye movements in reading are thus utilized as a temporal interface between a stable physical stimulus—written text—and brain systems that have evolved to process signals whose temporal structure is constrained by the characteristics of our vocal tract,” the paper says.

The paper notes, however, that these finding apply in the case of persons with low reading skills. The ‘sight reading’, capability of expert readers may define a different relationship between speech processing and reading rates. This may help understanding low or impaired reading skills, or how non-native readers develop reading ability, the paper says.

The saccade The eye can sharply focus on only a very small field at a time. While viewing an object, the head and body do not move, but the muscles of the eye get the eye to rapidly scans the parts of the object, to build up a picture. These rapid movements are called saccades and can last just a fiftieth of a second. When reading, again, the head does not move, but the eye scans the writing, in steps, with short wait at each step, when a bit of written matter is read. The pauses, with the step that leads to them, take from a fifth to a quarter of a second.

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