Paulo Ventura

How Learning to Read Changes the Cortical Networks for Vision and Language

Reading, Writing, and Face Recognition Reading, not to mention writing and texting, is a relatively recent invention, and hence it is believed that a preliterate brain must adapt on the fly, so to speak, in learning how to process written words, rather than being able to rely upon evolutionarily ancient modifications of the visual system pathways. Dehaene et al. (p. 1359, published online 11 November) examined the neural response to a range of visual stimuli in three groups: illiterate adults, adults who learned to read as children, and adults who learned to read as adults. Reading induced a greater facility in processing horizontally oriented stimuli at early stages in the visual pathway and was also associated with the appearance of an area specialized for words. This gain of function appeared to occur at a cost—the area in the temporal cortex devoted to face processing shrank. Reading changes the mind. Does literacy improve brain function? Does it also entail losses? Using functional magnetic resonance imaging, we measured brain responses to spoken and written language, visual faces, houses, tools, and checkers in adults of variable literacy (10 were illiterate, 22 became literate as adults, and 31 were literate in childhood). As literacy enhanced the left fusiform activation evoked by writing, it induced a small competition with faces at this location, but also broadly enhanced visual responses in fusiform and occipital cortex, extending to area V1. Literacy also enhanced phonological activation to speech in the planum temporale and afforded a top-down activation of orthography from spoken inputs. Most changes occurred even when literacy was acquired in adulthood, emphasizing that both childhood and adult education can profoundly refine cortical organization.

The locus of the orthographic consistency effect in auditory word recognition

In Experiments 1–2, we replicated with two different Portuguese materials the consistency effect observed for French by Ziegler and Ferrand (1998). Words with rimes that can be spelled in two different ways (inconsistent) produced longer auditory lexical decision latencies and more errors than did consistent words. In Experiment 3, which used shadowing, no effect of orthographic consistency was found. This task difference could reflect the confinement of orthographic influences to either decisional or lexical processes. In Experiment 4, we tried to untangle these two interpretations by comparing two situations in which a shadowing response was made contingent upon either a lexical or a phonemic criterion. A significant effect of orthographic consistency was observed only in lexically contingent shadowing. We thus argue that lexical but not sublexical processes are affected by orthographic consistency.

Categorical perception of speech sounds in illiterate adults

Children affected by dyslexia exhibit a deficit in the categorical perception of speech sounds, characterized by both poorer discrimination of between-category differences and by better discrimination of within-category differences, compared to normal readers. These categorical perception anomalies might be at the origin of dyslexia, by hampering the set up of grapheme-phoneme correspondences, but they might also be the consequence of poor reading skills, as literacy probably contributes to stabilizing phonological categories. The aim of the present study was to investigate this issue by comparing categorical perception performances of illiterate and literate people. Identification and discrimination responses were collected for a /ba-da/ synthetic place-of-articulation continuum and between-group differences in both categorical perception and in the precision of the categorical boundary were examined. The results showed that illiterate vs. literate people did not differ in categorical perception, thereby suggesting that the categorical perception anomalies displayed by dyslexics are indeed a cause rather than a consequence of their reading problems. However, illiterate people displayed a less precise categorical boundary and a stronger lexical bias, both also associated with dyslexia, which might, therefore, be a specific consequence of written language deprivation or impairment.

Does math education modify the approximate number system? A comparison of schooled and unschooled adults

Does math education contribute to refine the phylogenetically inherited capacity to approximately process large numbers? The question was examined in Western adults with different levels of math education. Unschooled adults who never received math education were compared to unschooled-instructed adults who did not attend regular school but received math education in adulthood, and to schooled adults who attended regular school in childhood. In the number-comparison task (Exp. 1), the unschooled group was slower and made more errors than the other groups both when numerical symbols and nonsymbolic dot collections were presented. In the forced-choice mapping task (Exp. 2), the unschooled group experienced more difficulty than the others in linking large nonsymbolic and symbolic quantities, as well as in matching purely nonsymbolic quantities. These results suggest that Western adults who did not receive math education have less precise approximate number skills than adults who acquired exact number competences through math education.

The locus of the orthographic consistency effect in auditory word recognition: Further evidence from French

Ventura, Morais, Pattamadilok, and Kolinsky (2004) found, for spoken Portuguese words, an orthographic consistency effect in lexical decision but not in standard shadowing (on-line repetition): words ending with phonological rimes that have several spellings led to longer decision times than words ending with phonological rimes that have only one spelling. This pattern of results was replicated in this study, using French, a language presenting a much higher degree of orthographic inconsistency than Portuguese. The observation of systematic associations between the effects of word orthographic consistency, word frequency and lexicality supports the hypothesis that lexical processing is critical to the occurrence of the consistency effect. Finally, the comparison of the word consistency effects obtained in French and in Portuguese suggests that their size depends on the overall consistency of the languages orthographic code.

Timing the impact of literacy on visual processing

Significance How does learning to read affect visual processing? We addressed this issue by scanning adults who could not attend school during childhood and either remained illiterate or acquired partial literacy during adulthood (ex-illiterates). By recording event-related brain responses, we obtained a high-temporal resolution description of how illiterate and literate adults differ in terms of early visual responses. The results show that learning to read dramatically enhances the magnitude, precision, and invariance of early visual coding, within 200 ms of stimulus onset, and also enhances later neural activity. Literacy effects were found not only for the expected category of expertise (letter strings), but also extended to other visual stimuli, confirming the benefits of literacy on early visual processing. Learning to read requires the acquisition of an efficient visual procedure for quickly recognizing fine print. Thus, reading practice could induce a perceptual learning effect in early vision. Using functional magnetic resonance imaging (fMRI) in literate and illiterate adults, we previously demonstrated an impact of reading acquisition on both high- and low-level occipitotemporal visual areas, but could not resolve the time course of these effects. To clarify whether literacy affects early vs. late stages of visual processing, we measured event-related potentials to various categories of visual stimuli in healthy adults with variable levels of literacy, including completely illiterate subjects, early-schooled literate subjects, and subjects who learned to read in adulthood (ex-illiterates). The stimuli included written letter strings forming pseudowords, on which literacy is expected to have a major impact, as well as faces, houses, tools, checkerboards, and false fonts. To evaluate the precision with which these stimuli were encoded, we studied repetition effects by presenting the stimuli in pairs composed of repeated, mirrored, or unrelated pictures from the same category. The results indicate that reading ability is correlated with a broad enhancement of early visual processing, including increased repetition suppression, suggesting better exemplar discrimination, and increased mirror discrimination, as early as ∼100–150 ms in the left occipitotemporal region. These effects were found with letter strings and false fonts, but also were partially generalized to other visual categories. Thus, learning to read affects the magnitude, precision, and invariance of early visual processing.

Reading acquisition enhances an early visual process of contour integration

The acquisition of reading has an extensive impact on the developing brain and leads to enhanced abilities in phonological processing and visual letter perception. Could this expertise also extend to early visual abilities outside the reading domain? Here we studied the performance of illiterate, ex-illiterate and literate adults closely matched in age, socioeconomic and cultural characteristics, on a contour integration task known to depend on early visual processing. Stimuli consisted of a closed egg-shaped contour made of disconnected Gabor patches, within a background of randomly oriented Gabor stimuli. Subjects had to decide whether the egg was pointing left or right. Difficulty was varied by jittering the orientation of the Gabor patches forming the contour. Contour integration performance was lower in illiterates than in both ex-illiterate and literate controls. We argue that this difference in contour perception must reflect a genuine difference in visual function. According to this view, the intensive perceptual training that accompanies reading acquisition also improves early visual abilities, suggesting that the impact of literacy on the visual system is more widespread than originally proposed.

Schooling in western culture promotes context-free processing

Culture has been shown to influence the way people apprehend their physical environment. Cognitive orientation is more holistic in East Asian cultures, which emphasize relationships and connectedness among objects in the field, than in Western cultures, which are more prone to focus exclusively on the object and its attributes. We investigated whether, beyond, or in conjunction with culture, literacy and/or schooling may also have an influence on this cognitive orientation. Using the Framed-Line Test both in Portugal and in Thailand, we compared literate schooled adults with two groups of unschooled adults: one of illiterates and one of ex-illiterates. As in former studies on Western people, Portuguese-schooled literates were more accurate in the absolute task than in the relative task. In contrast, Portuguese illiterates and ex-illiterates were more accurate in the relative task than in the absolute task. Such an effect of schooling was not observed in the Thai groups, all of whom performed better on the relative task. Thus, the capacity to abstract from contextual information does not stem only from passive exposure to the culture or the physical environment of Western countries. Western schooling, as part of or in addition to culture, is a crucial factor.

The fur of the crocodile and the mooing sheep: A study of a patient with a category-specific impairment for biological things.

We report a single case study of a brain-damaged patient, ER, who showed a remarkably consistent category-specific deficit for living things. His impairment was observed across tasks (naming, definition, matching, drawing from memory, questionnaires), input modalities (visual, verbal, nonverbal auditory), and output modalities (verbal vs. pointing or visual matching responses) as well as for different types of knowledge. Although visual knowledge of living things was severely affected, his category-specific impairment in nonverbal sound recognition is inconsistent with models of category-specific deficits based on pre-semantic visual descriptions. ERs deficit cannot fully be explained by item typicality, word frequency, visual complexity, homomorphy, age of acquisition, value to perceiver, or modality of transaction. Furthermore, in ER, contextual cues were even slightly detrimental for the recognition of animals. ERs naming and recognition errors were constrained by the categorical structure of the knowledge base: In most cases they respected both the second- and first-order superordinates. In particular, ERs knowledge of shared categorical properties related to biological function was almost spared. This result is compatible with the idea that, for living things, shared functional properties and shared perceptual properties are strongly correlated. Feature-based models assuming perceptual vs. functional semantic components cannot account for ERs deficit, since for living things he was impaired on both kinds of features to a similar extent. ERs behaviour is quite consistent with the notion that conceptual knowledge is organised categorically in the brain, with one or several specialised subsystems for biologically related entities.

Literacy acquisition reduces the influence of automatic holistic processing of faces and houses

Writing was invented too recently to have influenced the human genome. Consequently, reading acquisition must rely on partial recycling of pre-existing brain systems. Prior fMRI evidence showed that in literates a left-hemispheric visual region increases its activation to written strings relative to illiterates and reduces its response to faces. Increasing literacy also leads to a stronger right-hemispheric lateralization for faces. Here, we evaluated whether this reorganization of the brains face system has behavioral consequences for the processing of non-linguistic visual stimuli. Three groups of adult illiterates, ex-illiterates and literates were tested with the sequential composite face paradigm that evaluates the automaticity with which faces are processed as wholes. Illiterates were consistently more holistic than participants with reading experience in dealing with faces. A second experiment replicated this effect with both faces and houses. Brain reorganization induced by literacy seems to reduce the influence of automatic holistic processing of faces and houses by enabling the use of a more analytic and flexible processing strategy, at least when holistic processing is detrimental to the task.