Orthographic familiarity, phonological legality and number of orthographic neighbours affect the onset of ERP lexical effects

Alice M Proverbio,Roberta Adorni

doi:10.1186/1744-9081-4-27

Alice M Proverbio, Roberta Adorni

Open Access

https://doi.org/10.1186/1744-9081-4-27

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Abstract

BackgroundIt has been suggested that the variability among studies in the onset of lexical effects may be due to a series of methodological differences. In this study we investigated the role of orthographic familiarity, phonological legality and number of orthographic neighbours of words in determining the onset of word/non-word discriminative responses.MethodsERPs were recorded from 128 sites in 16 Italian University students engaged in a lexical decision task. Stimuli were 100 words, 100 quasi-words (obtained by the replacement of a single letter), 100 pseudo-words (non-derived) and 100 illegal letter strings. All stimuli were balanced for length; words and quasi-words were also balanced for frequency of use, domain of semantic category and imageability. SwLORETA source reconstruction was performed on ERP difference waves of interest.ResultsOverall, the data provided evidence that the latency of lexical effects (word/non-word discrimination) varied as a function of the number of a word's orthographic neighbours, being shorter to non-derived than to derived pseudo-words. This suggests some caveats about the use in lexical decision paradigms of quasi-words obtained by transposing or replacing only 1 or 2 letters. Our findings also showed that the left-occipito/temporal area, reflecting the activity of the left fusiform gyrus (BA37) of the temporal lobe, was affected by the visual familiarity of words, thus explaining its lexical sensitivity (word vs. non-word discrimination). The temporo-parietal area was markedly sensitive to phonological legality exhibiting a clear-cut discriminative response between illegal and legal strings as early as 250 ms of latency.ConclusionThe onset of lexical effects in a lexical decision paradigm depends on a series of factors, including orthographic familiarity, degree of global lexical activity, and phonologic legality of non-words.

Highlights

It has been suggested that the variability among studies in the onset of lexical effects may be due to a series of methodological differences
The role of orthographical well-formedness and visual familiarity in reading Overall, it seems that while the left occipito/temporal area is sensitive to word visual familiarity, the temporo/parietal area is more sensitive to phonological legality
The data provided evidence that: (i) the latency of the lexical effect varies as a function of the number of a word's orthographic neighbours, being faster to non-derived than to derived pseudo-words; this suggests some caveats in the use in lexical decision paradigms of quasi-words obtained by transposing or replacing only 1 or 2 letters

Summary

Introduction

It has been suggested that the variability among studies in the onset of lexical effects may be due to a series of methodological differences. The onset of lexical processing as described in the available literature seems to range from 110 ms [4,6] to 150 ms [1822] up to 300/400 ms [15,17,23] This wide variability seems to depend heavily on methodological factors [6,24] such as differences among studies in experimental parameters (e.g. word luminance, length, duration, frequency of use, semantic category or domain, grammatical class, repetition rate, familiarity, abstractness, ISI, SOA) and task modalities (lexical decision, orthographic or phonetic decision, semantic priming, SRVP, terminal word paradigm, etc.). Another study [28] found that the N1 and N400 components to semantically incongruous words had slower latencies in simultaneous interpreters (mastering up to 5–8 languages) than in age-matched monolingual controls It seems that semantic processing relies on systems with limited capacity, and the speed of processing may depend on multiple factors such as those previously reported. One obvious factor in the inconsistency among studies is the inter-study variability in signal-to-noise ratio for ERP averages: in some studies, ERP waveforms are so noisy that the first reliable component showing stimulus-related effects necessarily becomes the largest in amplitude and most resistant to noise (N400), the late latency of which is thereafter considered the onset of semantic processing

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