Multiple simultaneous stimulus presentation facilitates lexical processing

Bilateral presentation of two copies of the same word leads to faster lexical decisions compared to unilateral presentation alone (bilateral gain). This has implications for theories of interhemispheric interaction, because it suggests that, under certain conditions, both hemispheres cooperate rather than inhibit each other or act independently. Experiment 1 confirmed that the bilateral gain is word-specific and does not occur for pseudowords. Whereas the bilateral gain proved to be present for words of different word frequencies, results of Experiment 2 suggest that it is slightly stronger for high-frequency words compared to words of lower frequencies. Experiment 3 revealed that higher numbers of stimuli (two versus four copies of the same word/pseudoword) presented at the same time lead to an additional improvement of word processing. These results support a neurobiological model of word representation assuming that words are cortically represented in widely distributed interhemispheric cell assemblies. Summation of activity in such assemblies leads to faster and more reliable ignition of the network.