Masked repetition priming of letter-in-string identification: an ERP investigation

In a post-cued letter identification task, participants were presented with 7-letter nonword target stimuli that were formed of a random string of consonants (DCMFPLR) or a pronounceable sequence of consonants and vowels (DAMOPUR). Targets were preceded by briefly presented pattern-masked primes that could be the same sequence of letters as the target, composed of seven different letters, or sharing either the first or last five letters of the target. There was some evidence for repetition priming effects that were independent of target type in an early component, the N/P150, thought to reflect the mapping of visual features onto letter representations, and that is insensitive to orthographic structure. Following this, pronounceable nonwords showed significantly greater repetition priming effects than consonant strings, in line with the behavioral results. Initial versus final overlap only started to influence target processing at around 200-250ms post-target onset, at about the same time as the effects of target type emerged. The results are in line with a model where the initial parallel mapping of visual features onto a location-specific orthographic code is followed by the subsequent activation of location-invariant orthographic and phonological codes.