The Effects of Working Memory, Processing Speed, Inhibition, and Rapid Naming on Single-Word Reading and Reading Comprehension

Christopher and his colleagues examined whether two aspects of executive functioning (working memory and inhibition) and two aspects of speed (processing speed and rapid naming) predict or are associated with single-word reading and reading comprehension.

Working memory may affect single-word reading primarily during the early stages of learning to read. At this stage, the reader must connect letters and vowel marks with their corresponding sounds and integrate the letters and sounds into a word. Working memory may also affect reading comprehension. To understand a sentence, we must retain the meanings of the words we have read and manipulate them mentally. To understand a paragraph, we must retain and manipulate the meanings of the sentences we have read. To understand a text, we must retain and manipulate the meanings of the paragraphs we have read.

Processing speed may affect single-word reading during the early stages of reading development, when the connection between letters, vowel marks, and sounds must become rapid, fluent, and automatic. Processing speed may also affect reading comprehension. The more quickly a person reads words and matches them to their representations in their knowledge base, the more quickly and effectively they can understand what they are reading. Similarly, the faster the meanings of sentences and ideas in a text are processed, the better reading comprehension is likely to be. More efficient reading helps readers learn and store a larger number of new words. This, in turn, improves word-reading ability, which further supports reading comprehension, and so on.

In this study, the researchers defined inhibition as the ability to suppress old information and ignore irrelevant information in order to remain focused on the goal and on relevant stimuli. When reading a sentence with an ambiguous word that has more than one meaning, the reader must suppress the meanings that do not fit the context and retain the meaning that is appropriate for the sentence. At a more global level, reading comprehension requires readers to suppress inaccurate interim interpretations of the text as a whole while reading. Children with reading-comprehension difficulties have been found to show deficits in inhibition.

Rapid naming may be related to single-word reading because rapid-naming tests require an automatic, fluent, and rapid association between a sound and a symbol—the same operation required in reading.

The study included 483 children between the ages of 8 and 16, who were divided into two age groups. The younger group, aged 8–10, included 266 children, and the older group included 217 children. Approximately one-quarter of the children had a reading disability, and one-fifth had attention-deficit/hyperactivity disorder.

Working memory was assessed using a Sentence Span task. In this task, the children completed sentences and then recalled all the words they had completed. The children were also given a digit span task (repeating a series of digits).

Inhibition was measured using a test in which the children viewed numbers and were asked to press a button whenever the number 1 appeared after the number 9. In another task, they were asked to press either X or O according to the letter displayed on the screen. On some trials, a tone was played, and when they heard it, they were required to refrain from pressing the button.

Processing speed was assessed using a test in which the children had to identify sequences of letters that were identical to a target sequence among distractors. In a similar task, they were asked to find pictures identical to a target picture among distractors.

Rapid naming was measured through the rapid naming of colors and objects.

Reading comprehension was assessed using a Woodcock-Johnson oral-language comprehension test in which the child listened to a short passage and was asked to supply a missing word. Listening comprehension, single-word reading both with and without a speed component, and spelling were also assessed.

The results:

Working memory was found to predict both single-word reading and reading comprehension. In other words, as working-memory ability increased, scores in single-word reading and reading comprehension also increased.

Processing speed predicted single-word reading and was also a marginal predictor of reading comprehension.

Inhibition and rapid-naming speed did not predict either reading comprehension or single-word reading. In other words, they did not explain additional variance in word reading or reading comprehension beyond that explained by the other cognitive factors. This pattern of results was found in both age groups.

Why Were Inhibition and Rapid Naming Not Associated with Single-Word Reading and Reading Comprehension?

Inhibition was not associated with reading when it was analysed together with the other three factors: working memory, processing speed, and rapid naming. However, when inhibition was considered as the only cognitive factor, it was indeed associated with both single-word reading and reading comprehension. This suggests that the other three factors absorbed or masked the effect of inhibition on reading.

The rapid automatized naming, or RAN, test used in this study involved colors and objects. No association was found between performance on this test and reading. The researchers therefore examined whether RAN tasks involving digits and letters were associated with reading. They found that when letter- and digit-naming tasks were added to the color- and object-naming tasks, rapid naming predicted single-word reading but did not predict reading comprehension.

The researchers also asked to what extent the relationship between word reading and reading comprehension was driven by general intelligence. They found that general intelligence predicted both word reading and reading comprehension independently of the four other cognitive factors. General intelligence was more strongly associated with reading comprehension than with single-word reading.

Because many of the children in the study had attention-deficit/hyperactivity disorder, the researchers conducted an additional analysis that excluded those children. This analysis included 215 children in the younger age group and 174 children in the older age group. The overall pattern of findings remained unchanged.

Christopher, M. E., Miyake, A., Keenan, J. M., Pennington, B., DeFries, J. C., Wadsworth, S. J., ... & Olson, R. K. (2012). Predicting word reading and comprehension with executive function and speed measures across development: A latent variable analysis. Journal of Experimental Psychology: General, 141(3), 470.