Letters are often repeated in words in many languages. The present work explored the mechanisms underlying processing of repeated and unique letters in strings across three experimental paradigms. In a 2AFC perceptual identification task, the insertion but not the deletion of a letter was harder to detect when it was repeated than when it was unique (Exp. 1). In a masked primed same-different task, deletion primes produced the same priming effect regardless of deletion type (repeated, unique; Exp. 2), but insertion primes were more effective when the additional inserted letter created a repetition than when it did not (Exp. 3). In a same-different perceptual identification task, foils created by modifying a repetition, by either repeating the wrong letter or substituting a repeated letter, were harder to reject than foils created by modifying unique letters (Exp. 4). Thus, repetition effects were task-dependent. Since considering representations alone would suggest repetition effects would always occur or never occur, this indicates the importance of modelling task-specific processes. The similarity calculations embedded in the Overlap Model (Gomez et al., 2008) appeared to always predict a repetition effect, but its decision rule for the task of Experiment 1 allowed it to predict the asymmetry between insertions and deletions. In the Letters in Time and Retinotopic Space (LTRS; Adelman, 2011) model, repetition effects arise only from briefly presented stimuli as their perception is incomplete. It was therefore consistent with Experiments 2-4 but required a task-specific response bias to account for the insertion-deletion asymmetry of Experiment 1.
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CORE (COnnecting REpositories)