Hemispheric Differences in the Processing of Words Learned Early Versus Later in Childhood

The research investigated whether there are hemispheric differences in processing for words acquired early in childhood (early AoA) and words acquired later in childhood (late AoA). We hypothesized that because of recent evidence suggesting that there is a right hemisphere dominance in early childhood, early AoA words would be represented in the right hemisphere, and late AoA words would be represented in the left hemisphere. This hypothesis differs from an early view that late AoA words would be represented in the left hemisphere, and early AoA words would be represented in both hemispheres (Gazzaniga, 1974). We report two experiments using the divided visual field (DVF) technique. The results showed that there was a right visual field (RVF)/left hemisphere (LH) advantage only for late AoA words. For early AoA words, there was a left visual field (LVF)/right hemisphere advantage (RH). Implications for theories of hemispheric differences in word processing are discussed.     

Dichotic listening in a child recovering from acquired aphasia

A right-handed 6-year-old boy with acquired aphasia of left-hemisphere origin was investigated with various dichotic listening tasks 8 and 13 months after onset of the symptoms. Total right ear extinction was found repeatedly using both numbers and words as stimuli. Furthermore, magnitude of right ear extinction was not amenable to modification through verbal training, but disappeared when words were presented to the child's right ear with simultaneous white noise to the left ear. The findings are discussed in terms of the plasticity of cerebral dominance during childhood.     

Continuity and change in children's longitudinal neural responses to numbers

Human children possess the ability to approximate numerical quantity nonverbally from a young age. Over the course of early childhood, children develop increasingly precise representations of numerical values, including a symbolic number system that allows them to conceive of numerical information as Arabic numerals or number words. Functional brain imaging studies of adults report that activity in bilateral regions of the intraparietal sulcus (IPS) represents a key neural correlate of numerical cognition. Developmental neuroimaging studies indicate that the right IPS develops its number‐related neural response profile more rapidly than the left IPS during early childhood. One prediction that can be derived from previous findings is that there is longitudinal continuity in the number‐related neural responses of the right IPS over development while the development of the left IPS depends on the acquisition of numerical skills. We tested this hypothesis using fMRI in a longitudinal design with children ages 4 to 9. We found that neural responses in the right IPS are correlated over a 1–2‐year period in young children whereas left IPS responses change systematically as a function of children's numerical discrimination acuity. The data are consistent with the hypothesis that functional properties of the right IPS in numerical processing are stable over early childhood whereas the functions of the left IPS are dynamically modulated by the development of numerical skills.     

Growth functions for rapid remembering

Children between ages 9 and 13 were tested for recognizing and remembering words from 6- and 12-word lists. Opportunities for using deliberate mnemonics were severely restricted. Developmental functions showed different growth patterns for remembering the items in a short list than for remembering order, and different patterns for storing items from a long list than for retrieving them. However, none of these functions was parallel to the growth function of rapid word recognition. This absence of parallel growth contradicted a hypothesis that memory develops when item recognition develops. The data suggested, instead, that modest but reliable gains in rapid processes of storage and retrieval contribute to memory development during middle childhood.     

What is in a word? No versus Yes differentially engage the lateral orbitofrontal cortex

The words "No" and "Yes" are involved in conditioning to prohibit or encourage behavior, respectively. The authors, therefore, hypothesized that these words would be attributed to endogenous valence, activating neuronal circuits involved with valence and emotional control. Functional MRI (fMRI) at 4 Tesla was used to record regional brain activity while participants were exposed to emphatic vocalizations of the words. Results showed that No and Yes were associated with opposite brain-behavior responses; while No was negatively valenced, produced slower response times, and evoked a negative signal in the right lateral orbitofrontal cortex (OFC), Yes was positively valenced, produced faster response times, and evoked a positive signal in a contiguous region of the OFC. Attribution of negative valence to No and trait anger control were associated with increased responsivity of the OFC to No. Inasmuch as sensitivity to the prohibitive command No develops during childhood through interaction with primary caregivers as the first social objects, our findings may implicate the lateral OFC in the neurobiology of emotion regulation and subsequent social development.     

Right-hemisphere reading in a case of developmental deep dyslexia

The right-hemisphere hypothesis of deep dyslexia has received support from functional imaging studies of acquired deep dyslexia following damage to the left cerebral hemisphere, but no imaging studies of cases of developmental deep dyslexia, in which brain damage is not suspected, have been reported. In this paper, we report the first evidence of right hyperactivation in an adult case of developmental deep dyslexia. Hyperactivation was observed in the right inferior frontal cortex during functional magnetic resonance imaging (fMRI) of the oral reading of imageable content words and nonwords to which imageable lexical responses were frequently made. No evidence of right hyperactivation was observed in the oral reading of function words, nor during the naming of imageable words in response to pictured objects. The results reveal strategic and selective use of right-hemisphere functions for particular types of written stimuli. We propose that children with developmental deep dyslexia compensate for their lack of phonological skills by accessing right-hemisphere imageable associations that provide a mnemonic for linking written forms to spoken names.     

Right-hemisphere reading in a case of developmental deep dyslexia

The right-hemisphere hypothesis of deep dyslexia has received support from functional imaging studies of acquired deep dyslexia following damage to the left cerebral hemisphere, but no imaging studies of cases of developmental deep dyslexia, in which brain damage is not suspected, have been reported. In this paper, we report the first evidence of right hyperactivation in an adult case of developmental deep dyslexia. Hyperactivation was observed in the right inferior frontal cortex during functional magnetic resonance imaging (fMRI) of the oral reading of imageable content words and nonwords to which imageable lexical responses were frequently made. No evidence of right hyperactivation was observed in the oral reading of function words, nor during the naming of imageable words in response to pictured objects. The results reveal strategic and selective use of right-hemisphere functions for particular types of written stimuli. We propose that children with developmental deep dyslexia compensate for their lack of phonological skills by accessing right-hemisphere imageable associations that provide a mnemonic for linking written forms to spoken names.     

Right hemisphere superiority in processing new symbols for arithmetic operators

A left ear advantage for solving dichotically-presented arithmetic problems was observed in subjects when nonsense words were substituted for familiar operator names (“plus”, “minus”, etc.). The expected right ear advantage was observed when the same problems were solved by the same subjects when the familiar operator names were presented. Since neither the task nor the nonsense words could produce the left ear advantage by themselves, it is hypothesized that introduction of the nonsense symbols created a novel situation which recruited greater functional participation by the right cerebral hemisphere. Accommodating to new symbols for previously assimilated concepts is a common demand in the learning process of formal systems. Thus, the functions of the left and right hemispheres appear to take interactive roles during learning.     

Dissociable effects of auditory attention switching and stimulus–response compatibility

Using a task-switching variant of dichotic listening, we examined the ability to intentionally switch auditory attention between two speakers. We specifically focused on possible interactions with stimulus–response compatibility. In each trial, two words, one spoken by a male and another by a female, were presented dichotically via headphones. In one experimental group, two animal names were presented, and the relevant animal had to be judged as smaller or larger than a sheep by pressing a left or right response key. In another group, two number words were presented and had to be judged as smaller or larger than 5. In each trial, a visual cue indicated the gender of the relevant speaker. Performance was worse when the gender of the relevant speaker switched from trial to trial. These switch costs were larger for animal names than for number words, suggesting stronger interference with slower access to semantic categories. Responses were slower if the side of the target stimulus (as defined by the relevant gender) was spatially incompatible with the required response (as defined by the size judgment). This stimulus–response compatibility effect did not differ across stimulus material and did not interact with attentional switch costs. These results indicate that auditory switch costs and stimulus–response compatibility effects are dissociable, referring to target selection and response selection, respectively.     

Hemispheric alpha asymmetries of stuttering males and nonstuttering males and females for words of high and low imagery

Alpha hemispheric asymmetries of nonstuttering males, nonstuttering females, and stuttering males were explored with electroencephalographic procedures during exposure to two lists of one-syllable words which the subjects were required to recall following presentation. One word list contained low-imagery words while the other contained high-imagery words. Stuttering males were found to have significantly less alpha in their right hemispheres, suggesting right hemispheric processing strategies. This finding was interpreted as supporting the “segmentation dysfunction” explanation of stuttering suggested by Moore and Haynes (1979b). Nonstuttering males showed less left than right alpha while nonstuttering females revealed no difference between their right and left hemispheres. Differences between nonstuttering males and females are discussed as being task and stimuli dependent relative to the segmental/nonsegmental nature of both task and stimuli. Differential hemispheric asymmetries for words of high or low-imagery were not observed.     

The availability of useful information to the right of fixation in reading

A series of experiments that examined the characteristics of useful information to the right of fixation during reading is reported. In Experiments 1 and 2, reading performance when the information available to the right of fixation was determined by a fixed number of letters was compared with reading performance when the information to the right of fixation was determined by a fixed number of words. Beyond making more letters visible, both experiments showed that preserving all of the letters of a word was of no special benefit to reading. By explicitly presenting parts of the word to the right of fixation as well as the fixated word, Experiments 3 and 4 followed up on the implication that readers utilize partial letter information from words. Both experiments showed that reading was improved by this partial information and that preserving three letters of the word to the right of fixation improved reading almost as much as presenting the entire word. The implications the results have for models of reading are discussed.     

The juvenile transition: A developmental switch point in human life history

This paper presents a new perspective on the transition from early to middle childhood (i.e., human juvenility), investigated in an integrative evolutionary framework. Juvenility is a crucial life history stage, when social learning and interaction with peers become central developmental functions; here it is argued that the “juvenile transition” is a developmental switch point in the human life history, when both sex-related and individual differences in reproductive strategies are expressed after the assessment period provided by early childhood. Adrenarche, the secretion of adrenal androgens starting at the beginning of middle childhood, is proposed as the endocrine mechanism mediating the juvenile transition. It is argued that, in connection with the stress system, adrenal androgens enable adaptive plasticity in the development of reproductive strategies through integration of environmental and genetic factors. Finally, evidence is reviewed of both sex-related and individual differences arising during the juvenile transition, in the domains of attachment and aggression. Juvenility plays a central role in the ontogeny of behavior and personality; this paper contributes to defining its place within an integrated model of human development.     

Asymmetrical perceptual load in lateralised word processing

We applied the Load Theory of attention (Lavie, 1995, 2005) to the case of distraction during processing of lateralised words presented in either the right or the left visual fields. Previous research (Brand-D'Abrescia & Lavie, 2007) showed that lexicality affects selective attention such that the number of letters in a search task only increases perceptual load and reduces irrelevant distractor effects for searches in nonwords but not in words. The present study examined the hypothesis that the effect of lexicality on distractor processing would be stronger for words presented to the left compared to the right hemisphere. The results supported this hypothesis and their implications for attention to words in the two cerebral hemispheres are discussed. We suggest that the efficiency of attentional selection differed because perceptual load in the visual fields taxed processing depending on hemispheric language expertise.     

Shift of visual field preference for Hebrew words in native speakers learning to read

Lateralization for Hebrew words was tested in both the visual and auditory modalities in Israeli children learning to read their native language, Hebrew. A left visual field preference for tachistoscopically presented words was found in the second graders in contrast to a right visual field preference for the same words in the third graders. Children in both grades showed a right ear dominance for similar words presented dichotically. These data suggest right hemisphere involvement in acquiring reading skills of a native language.     

The dynamic functions of social cues during children's word learning

Children learn words in a social environment, facilitated in part by social cues from caregivers, such as eye-gaze and gesture. A common assumption is that social cues convey either perceptual or social information, depending on the age of the child. In this review of research on word learning and social cues during early childhood, we propose that (1) the functions of social cues are not categorically perceptual or social, and (2) social cues support word learning in four interdependent ways: by helping children to orient attention, extract relevant information, disambiguate referents, and understand others' referential intent. We conclude with specific recommendations for theory-building and suggest that the dynamic and complex functions of social cues need to be accounted for in any complete theory of word learning.     

Phonological processing during silent reading in teenagers who are deaf/hard of hearing: an eye movement investigation

There has been considerable variability within the literature concerning the extent to which deaf/hard of hearing individuals are able to process phonological codes during reading. Two experiments are reported in which participants’ eye movements were recorded as they read sentences containing correctly spelled words (e.g., church), pseudohomophones (e.g., cherch), and spelling controls (e.g., charch). We examined both foveal processing and parafoveal pre‐processing of phonology for three participant groups—teenagers with permanent childhood hearing loss (PCHL), chronological age‐matched controls, and reading age‐matched controls. The teenagers with PCHL showed a pseudohomophone advantage from both directly fixated words and parafoveal preview, similar to their hearing peers. These data provide strong evidence for phonological recoding during silent reading in teenagers with PCHL.     

Hemispheric asymmetries and cognitive flexibility: an ERP and sLORETA study

Although functional cerebral asymmetries (FCAs) affect all cognitive domains, their modulation of the efficacy of specific executive functions is largely unexplored. In the present study, we used a lateralized version of the task switching paradigm to investigate the relevance of hemispheric asymmetries for cognitive control processes. Words were tachistoscopically presented in the left (LVF) and right visual half field (RVF). Participants had to categorise the words either based on their initial letters, or according to their word type. On half of the trials the task changed (switch trials) whereas on the other half it stayed the same (repeat trials). ERPs were recorded and the neural sources of the ERPs were reconstructed using standardised low resolution brain electromagnetic tomography (sLORETA). In the word type task, participants were faster on repeat trials when stimuli were presented in the RVF. In contrast, in the initial letter task participants were faster on repeat trials and in general more accurate after stimulus presentation in the LVF. In both tasks, no hemispheric asymmetries in reaction times were observed on switch trials. On the electrophysiological level, we observed a left lateralization of the N1 that was mediated by activation in the left extrastriate cortex as well as a greater positivity of the P3b after stimulus presentation in the RVF compared to the LVF that was mediated by activation in the superior parietal cortex. These results show that FCAs affect the neurophysiological correlates of executive functions related to task switching. The relation of neurophysiological and behavioural asymmetries is mediated by task complexity, with more complex tasks leading to more interhemispheric interaction and smaller left-right differences in behavioural measures. These findings reveal that FCAs are an important modulator of executive functions related to cognitive flexibility.     

Reading habits for both words and numbers contribute to the SNARC effect

This study compared the spatial representation of numbers in three groups of adults: Canadians, who read both English words and Arabic numbers from left to right; Palestinians, who read Arabic words and Arabic-Indic numbers from right to left; and Israelis, who read Hebrew words from right to left but Arabic numbers from left to right. Canadians associated small numbers with left and large numbers with right space (the SNARC effect), Palestinians showed the reverse association, and Israelis had no reliable spatial association for numbers. These results suggest that reading habits for both words and numbers contribute to the spatial representation of numbers.     

Influence of affective valence on working memory processes

Recent research has revealed widespread effects of emotion on cognitive function and memory. However, the influence of affective valence on working or short-term memory remains largely unexplored. In two experiments, the present study examined the predictions that negative words would capture attention, that attention would be difficult to disengage from such negative words, and that the cost of attention switching would increase the time required to update information in working memory. Participants switched between two concurrent working memory tasks: word recognition and a working memory digit updating task. Experiment 1 showed substantial switching cost for negative words, relative to neutral words. Experiment 2 replicated the first experiment, using a self-report measure of anxiety to examine if switching cost is a function of an anxiety-related attention bias. Results did not support this hypothesis. In addition, Experiment 2 revealed switch costs for positive words without the effect of the attention bias from anxiety. The present study demonstrates the effect of affective valence on a specific component of working memory. Moreover, findings suggest why affective valence effects on working memory have not been found in previous research.