Top-down processing and the suffix effect in young and older adults

The suffix effect has generally been viewed as reflecting an automatic component involving the terminal item and a component susceptible to top-down influences involving the preterminal items (Balota & Engle, 1981). Recent findings have raised questions about this widely accepted view of the suffix effect by showing that the terminal component is not insensitive to top-down influences (Bloom & Watkins, 1999). In the present study, we attempted to uncover the source of these contradictory findings by assessing whether the terminal item's susceptibility to top-down influences might depend on subjects' first-hand experience of the extent to which recall is affected by the suffix. Furthermore, we examined whether age differences in the suffix effect could be attributed to age-related declines in inhibitory processes. Our findings supported both predictions.     

Cross-modal re-mapping influences the Simon effect

Tagliabue, Zorzi, Umiltà, and Bassignani (2000) showed that one's practicing of a spatially incompatible task influences performance in a Simon task even when the interval between the two tasks is as long as 1 week. In the present study, three experiments were conducted to investigate whether such an effect could be found in a cross-modal paradigm, whereby stimuli in the two tasks were presented in different modalities. Subjects performed either compatible or incompatible mappings in an acoustic spatial compatibility task and, after an interval of 5 min, 24 h, or 7 days, performed a visual Simon task. Results show that the spatially incompatible mapping task affected performance in the Simon task: The Simon effect was absent for all three intervals. This pattern is similar to the results of the Tagliabue et al. study, in which both tasks were performed in the same (visual) modality. Our findings disprove possible explanations based on episodic/contextual effects and support the hypothesis of a long-lasting spatial remapping that is not modality specific.     

Selective impairment of lexical stress assignment in an Italian-speaking aphasic patient

Psycholinguistic speech production models assume that lexical stress is stored and accessed separately during phonological encoding. We address the questions of the storage and computation of lexical stress in a case study of an Italian-speaking patient with an impairment of lexical stress assignment in naming, reading, and repeating single words. The patient's stress error pattern and his performance on tasks examining lexical stress in perception suggest an impairment in the retrieval of the stress pattern of irregular words. In contrast, his assignment of stress to nonstored phonological forms suggests that the computation of stress is unimpaired.     

Interhemispheric communication via direct connections for alternative meanings of ambiguous words

A priming experiment was used to investigate Burgess and Simpson's (1988) claim that interhemispheric cooperation plays an essential role in the interpretation of ambiguous text. In doing so, the merits of two models of interhemispheric cooperation, the homotopic inhibition theory (Cook, 1986) and the direct connections model (Collins & Coney, 1998), were examined. Priming of alternative meanings of ambiguous words was measured using homographs and their dominant (e.g., BARK-DOG) and subordinate meanings (e.g., BARK-TREE) as related pairs in a lexical decision task, with normal university students as subjects. Stimulus pairs were temporally separated by stimulus onset asynchronies (SOAs) of 180 and 350 ms and were independently projected to the left or right visual fields (LVF or RVF). At the shorter SOA, priming was restricted to LVF-RVF presentations, with homograph primes directed to the LVF equally facilitating responses to RVF targets which were associated with their dominant and subordinate meanings. This suggests that within 180 ms, a homograph projected to the right hemisphere activates a range of alternative meanings in the left hemisphere. At an SOA of 350 ms, LVF-RVF priming was obtained along with RVF-LVF and RVF-RVF priming. Evidently at this stage of processing, an ambiguous word directed to either hemisphere activates a range of alternative meanings in the contralateral hemisphere, while RVF primes also activate subordinate, but not dominant meanings in the left hemisphere. A homograph directed to the LVF did not activate dominant or subordinate meanings within the right hemisphere at either SOA. Generally, ambiguous words directed to either hemisphere activated a more extensive array of meanings in the contralateral hemisphere than in the hemisphere to which the prime was directed. This confirms the importance of interhemispheric cooperation in generating alternate meanings of ambiguous words. Strong support was found for the direct connections model (Collins & Coney, 1998), but no support for the homotopic inhibition theory (Cook, 1986).     

Age-related differences in inference revision processing

In comparison to younger adults, older adults demonstrate deficiencies in cognitive and linguistic abilities. Such cognitive factors that decline with age include working memory capacity and inhibitory abilities. The purpose of the present investigation was to measure differences in time course processing of inference revision abilities, as well as working memory, as they exist relative to adult age differences. Fifteen neurologically intact older adults and 15 younger adults participated in this study. A cross-modal lexical priming paradigm was chosen as the measure of the inference revision task; the listening span task of Tompkins, Bloise, Timko, and Baumgaertner (1994) was selected as the measure of working memory. Both groups demonstrated normal priming effects. No age-related differences were found on the working memory measure. Age-related differences did emerge on inferencing abilities. A significant correlation emerged between the older group's performance on comprehending inference revisions and their working memory capacity. Generally, inhibitory abilities and working memory capacity appeared to adversely affect older participant's performance.     

Sentence processing strategies in healthy seniors with poor comprehension: an fMRI study

We used fMRI to examine patterns of brain recruitment in 22 healthy seniors, half of whom had selective comprehension difficulty for grammatically complex sentences. We found significantly reduced recruitment of left posterolateral temporal [Brodmann area (BA) 22/21] and left inferior frontal (BA 44/6) cortex in poor comprehenders compared to the healthy seniors with good sentence comprehension, cortical regions previously associated with language comprehension and verbal working memory, respectively. The poor comprehenders demonstrated increased activation of left prefrontal (BA 9/46), right dorsal inferior frontal (BA 44/6), and left posterior cingulate (BA 31/23) cortices for the grammatically simpler sentences that they understood. We hypothesize that these brain regions support an alternate, nongrammatical strategy for processing complex configurations of symbolic information. Moreover, these observations emphasize the crucial role of the left perisylvian network for grammatically guided sentence processing in subjects with good comprehension.     

Crossmodal temporal order and processing acuity in developmentally dyslexic young adults

We investigated crossmodal temporal performance in processing rapid sequential nonlinguistic events in developmentally dyslexic young adults (ages 20-36 years) and an age- and IQ-matched control group in audiotactile, visuotactile, and audiovisual combinations. Two methods were used for estimating 84% correct temporal acuity thresholds: temporal order judgment (TOJ) and temporal processing acuity (TPA). TPA requires phase difference detection: the judgment of simultaneity/nonsimultaneity of brief stimuli in two parallel, spatially separate triplets. The dyslexic readers' average temporal performance was somewhat poorer in all six comparisons; in audiovisual comparisons the group differences were not statistically significant, however. A principal component analysis indicated that temporal acuity and phonological awareness are related in dyslexic readers. The impairment of temporal input processing seems to be a general correlative feature of dyslexia in children and adults, but the overlap in performance between dyslexic and normal readers suggests that it is not a sufficient reason for developmental reading difficulties.     

Stem homographs and lemma level representations

Previous studies have found that priming a target like cerr-o ("hill") with an unmasked stem-homograph (e.g., cerr-ar, "to close") or with an unmasked allomorph of a stem-homograph (e.g., cierr-a, "he/she/it closes") has an inhibitory effect on target recognition. We report evidence from stem-homograph priming studies that implicate both morphological parsing and lexical selection processes at the lemma level. We argue that stem-homograph inhibition is the product of lexical selection mechanisms that are engaged just when a fully ambiguous stimulus (here, an inflectional stem) must be assigned one of its viable interpretations in order to afford conscious perception of lexical identity.     

Exposure to violence and suicide risk in adolescents: a community study

The prevalence of violence exposure is relatively unexplored in adolescents in European communities, and reports on the association between exposure to community violence and suicidal behavior are rare. The aim of this study was to investigate (1) the prevalence of community violence in a European urban adolescent sample, (2) the relationship between exposure to community violence and suicidal ideation/deliberate self-harm, and (3) the influence of depressive symptoms and aggressive behavior on this relationship. Self-report surveys were administered to a representative school-based sample of 1509 adolescents in Antwerp (Belgium). The prevalence rate of violence exposure was still high but lower than that reported in U.S. communities. Suicidal ideation and deliberate self-harm were both related to violence exposure. The gender-specific influence of depressive symptomatology and aggressive behavior on the association between exposure to violence and suicidal behavior suggests the need for further research.     

Derivation by prefixation in Slovenian: two aphasia case studies

The present study is concerned with two Slovenian-speaking patients who were asked to produce, in various tasks, verbs, nouns, and adjectives derived by prefixation with prepositions. Despite differences due to their specific linguistic difficulties, both patients' performance was characterized by the differential processing of prefixes and remaining components of complex words. Prepositions in prefixation were mostly preserved, and less frequently substituted, regardless of the numerous errors produced in the remaining portion of the words. These errors seem clearly determined by the morphological structure of the words and therefore appear to be authentic morphological errors. These findings contribute to the theoretical debate on mental lexical representation, speaking in favor of a morphological decomposition in processing of prefixed complex words at different processing levels.