Hemisphere specialisation and inter-hemispheric cooperation during a phonological task: Effect of lexicality as assessed by the divided visual field approach

Abstract

In the presented experiment we explored the effect of lexicality on hemisphere specialisation and cooperation during a phonological task. The divided visual field (DVF) method with bilateral presentation (BVF) of redundant (identical) stimuli is considered an appropriate approach to assess inter-hemispheric cooperation (IHC). IHC is supposed to increase the efficiency of cognitive processes. Specifically, it has been shown that, compared to unilateral hemifield presentation, word processing is significantly more efficient if stimuli were presented under bilateral redundancy conditions. The performance enhancement during bilateral vs. unilateral presentation is called bilateral redundant gain (BRG). In the present experiment a DVF was used and participants were required to perform a rhyme detection task in two blocks, one in words and another one in pseudowords. Each item was presented in two different modes, one unilateral (right or left hemi-visual field) and another one bilateral (simultaneous redundant presentation). Unilateral trials allow one to study hemispheric specialisation, while bilateral redundant trials allow one to study inter-hemispheric cooperation. We obtained left hemisphere specialisation for both types of items (word, pseudoword). Moreover, words were more efficiently processed than pseudowords. Additionally, words were processed more efficiently in BVF than in unilateral presentation, inducing BRG. No similar effect was obtained for pseudowords. These results are discussed in respect to findings reported by other studies suggesting that hemispheric specialisation depends on lexicality. Moreover, compared to lexical decision tasks used in previous studies, the phonological task used in the present study seems to modulate the inter-hemispheric cooperation less.

List constituency and orthographic and phonological processing: A shift to high familiarity words from low familiarity words

“…Measures of laterality and hemispheric interaction were used to test the predictions. Four lines of evidence support the predictions: First, responses were faster to high familiarity words, pseudowords, and non-words in Experiment 1 than in Experiment 2 (see Table 1), as should occur if the task is easy and decisions are based on visual form instead of delaying either for the spread of activation to a phonological entry or the sequential conversion of graphemes to phonemes to sound out an unfamiliar letter string (Perrone-Bertolotti et al, 2013). Second, there was no laterality in the response time or accuracy data, suggesting that both hemispheres were similarly competent at performing the task.…”

“…Responses were relatively slow (see Table 1) supporting the contention that unfamiliar words are likely to trigger phonological processing to supplement unfamiliar orthography with a sound code (Perrone-Bertolotti et al, 2013). While response time was not a sensitive measure of hemispheric differences, likely due to high SE scores (see Table 1), accuracy did reveal differences.…”