An Investigation Of The Interaction Between The Visual Span And Word Superiority Effect In Central And Peripheral Reading.

Background: The visual span is hypothesized to be a low-level sensory bottleneck for
reading. While both reading speed and visual span size decreases with increasing retinal eccentricity, the decrease in reading speed cannot be completely accounted for by the decreases in visual span size alone. This implicates an additional limitation associated with peripheral reading processes. This study investigated the qualitative and quantitative interaction between word facilitation and letter recognition in central and
peripheral reading.
Methods: The visual span for trigrams (random 3 letter strings) and words were measured in 14 subjects between the ages of 20 and 30 years old with normal reading abilities. Letter and word sequences were presented to each participant at 0, 5, and 10 degrees retinal eccentricity for 100 milliseconds (ms). Words consisting of 3 letters were also presented to each subject at the same eccentricity and time parameters as the random letter sequences.
Results: Recognition of trigrams decreased as retinal eccentricity increased. The recognition of 3 letter words, when presented under the same experimental conditions, was better than the trigrams. A relationship was observed between the recognition of the letter sequences and words. If at least 50% of letters comprising trigrams were correctly recognized, word recognition was near 100%.
Conclusions: Word recognition is largely dependent on the ability to recognize individual letters. Processes involved in lexical inferences appear to be both qualitatively and quantitatively similar for central and peripheral reading processes. These results suggests that differences in the efficiency of lexical inferences do not limit peripheral reading.