Explaining the variance in reading ability in terms of psychological processes: What have we learned?

After years of confusion, the literature on individual differences in reading ability is finally beginning to coalesce around a small set of general conclusions that are endorsed by the vast majority of researchers. The most fundamental is that word decoding ability accounts for a very large proportion of the variance in reading ability at all levels. Variation in word decoding skill is primarily the result of differences in phonological abilities, rather than visual processes. Less-skilled readers are not characterized by a general inability to use context to facilitate word recognition. However, situations where such readers fail to utilize context to facilitate word recognition will arise when their slow and inaccurate decoding of words renders the context useless. Less-skilled readers display performance deficits on a wide variety of short-term memory tasks, probably due to an inability to efficiently employ various memory strategies, and most certainly due to inadequate phonological coding. Less-skilled readers may have comprehension deficits that are partially independent of word decoding skill. These problems probably arise because syntactic abilities and metacognitive strategies are inadequately developed.