Reaction times in lexical decision are more sensitive to a words' length and orthographic-neighborhood density when the stimulus is presented to the left visual field (LVF) than to the right visual field (RVF). We claim that the length effect is equivalent to the neighborhood effect, and propose a novel explanation of why the LVF, but not the RVF, is sensitive to density, based on different firing rates of abstract-letter representations encoding letters falling in the LVF versus RVF. We support this proposal with a large-scale implemented model of lexical decision utilizing spiking units, which provides a reasonable fit to the data from the English Lexicon Project under simulated central presentation, while replicating the observed hemifield asymmetries under simulated lateralized presentation. (Contains 3 tables and 7 figures.)