Reading Increases the Compositionality of Visual Word Representations

Reading causes widespread changes in the brain but its effect on visual word representations is unknown. Reading may facilitate visual processing by forming specialized detectors for longer strings, or by making word responses more predictable from single letters, that is by increasing compositionality. We provide evidence for the latter hypothesis by comparing readers and nonreaders of two Indian languages, Telugu and Malayalam. Readers showed decreased interactions between letters during visual search, which predicted their overall reading fluency. Brain imaging revealed increased compositionality in readers, whereby responses to bigrams were more predictable from single letters. This effect was specific to the lateral occipital region, where activations best matched behavior. Thus, reading facilitates visual processing by increasing the compositionality of visual word representations.