Alternating dual-task interference between visual words and faces

Faces, English words and Chinese characters: a study of dual-task interference in mono-and bilingual speakers

The many-to-many hypothesis suggests that face and visual-word processing tasks share neural resources in the brain, even though they show opposing hemispheric asymmetries in neuroimaging and neuropsychologic studies. Recently it has been suggested that both stimulus and task effects need to be incorporated into the hypothesis. A recent study found dual-task interference between face and text functions that lateralized to the same hemisphere, but not when they lateralized to different hemispheres. However, it is not clear whether a lack of interference between word and face recognition would occur for other languages, particularly those with a morpho-syllabic script, like Chinese, for which there is some evidence of greater right hemispheric involvement. Here, we used the same technique to probe for dual-task interference between English text, Chinese characters and face recognition. We tested 20 subjects monolingual for English and 20 subjects bilingual for Chinese and English. We replicated the prior result for English text and showed similar results for Chinese text with no evidence of interference with faces. We also did not find interference between Chinese and English text. The results support a view in which reading English words, reading Chinese characters and face identification have minimal sharing of neural resources.

The mechanisms supporting holistic perception of words and faces are not independent

The question of whether word and face recognition rely on overlapping or dissociable neural and cognitive mechanisms received considerable attention in the literature. In the present work, we presented words (aligned or misaligned) superimposed on faces (aligned or misaligned) and tested the interference from the unattended stimulus category on holistic processing of the attended category. In Experiment 1, we found that holistic face processing is reduced when a face was overlaid with an unattended, aligned word (processed holistically). In Experiment 2, we found a similar reduction of holistic processing for words when a word was superimposed on an unattended, aligned face (processed holistically). This reciprocal interference effect indicates a trade-off in holistic processing of the two stimuli, consistent with the idea that word and face recognition may rely on non-independent, overlapping mechanisms.

Faces and words are both associated and dissociated as evidenced by visual problems in dyslexia

Faces and words are traditionally assumed to be independently processed. Dyslexia is also traditionally thought to be a non-visual deficit. Counter to both ideas, face perception deficits in dyslexia have been reported. Others report no such deficits. We sought to resolve this discrepancy. 60 adults participated in the study (24 dyslexic, 36 typical readers). Feature-based processing and configural or global form processing of faces was measured with a face matching task. Opposite laterality effects in these tasks, dependent on left-right orientation of faces, supported that they tapped into separable visual mechanisms. Dyslexic readers tended to be poorer than typical readers at feature-based face matching while no differences were found for global form face matching. We conclude that word and face perception are associated when the latter requires the processing of visual features of a face, while processing the global form of faces apparently shares minimal-if any-resources with visual word processing. The current results indicate that visual word and face processing are both associated and dissociated-but this depends on what visual mechanisms are task-relevant. We suggest that reading deficits could stem from multiple factors, and that one such factor is a problem with feature-based processing of visual objects.