Connie Shears

Priming of strong semantic relations in the left and right visual fields: a time-course investigation

Prior time-course investigations of cerebral asymmetries in word processing have sometimes reported hemisphere differences in the onset and duration of semantic priming. In the current study, very strongly related word pairs (categorical associates such as arm-leg) were employed in a low relatedness proportion lexical decision priming paradigm. A range of prime-target stimulus onset asynchronies (SOAs: 150-800 ms) was included. Only very weak evidence was obtained for a LVF priming lag at the briefest SOA, while priming was bilateral at moderately long SOAs. We consider these data in the context of previous time-course studies and suggest that, when highly semantically similar word pairs are used, a right hemisphere priming lag is, at best, a very small effect.

Imageability and distributional typicality measures of nouns and verbs in contemporary English

Dissociations between noun and verb processing are not uncommon after brain injury; yet, precise psycholinguistic comparisons of nouns and verbs are hampered by the underrepresentation of verbs in published semantic word norms and by the absence of contemporary estimates for part-of-speech usage. We report herein imageability ratings and rating response times (RTs) for 1,197 words previously categorized as pure nouns, pure verbs, or words of balanced noun-verb usage on the basis of the Francis and Kučera (1982) norms. Nouns and verbs differed in rated imageability, and there was a stronger correspondence between imageability rating and RT for nouns than for verbs. For all word types, the image-rating-RT function implied that subjects employed an image generation process to assign ratings. We also report a new measure of noun-verbtypicality that used the Hyperspace Analog to Language (HAL; Lund & Burgess, 1996) context vectors (derived from a large sample of Usenet text) to compute the mean context distance between each word and all of thepure nouns andpure verbs. For a subset of the items, the resulting HAL noun-verb difference score was compared with part-of-speech usage in a representative sample of the Usenet corpus. It is concluded that this score can be used to estimate the extent to which a given word occurs in typical noun or verb sentence contexts in informal contemporary English discourse. The item statistics given in Appendix B will enable experimenters to select representative examples of nouns and verbs or to compare typical with atypical nouns (or verbs), while holding constant or covarying rated imageability.

Differential asymmetries for recognizing nouns and verbs: where are they?

To support categorical representation in the brain for grammatical class, it is necessary to show that noun-verb differences are attributable to parts of speech and not to covarying semantic factors. Prior visual-half field investigations of noun-verb processing have confounded grammatical class with imageability. The current study included numerous tests of differential noun-verb processing across visual fields for stimuli equated for imageability. Task (lexical decision, pronunciation) and list context (blocked vs. mixed lists) variables were examined in 168 right-handed participants. There was no reliable reduction of the right visual field advantage for moderately imageable nouns as compared with verbs. If there are qualitative hemisphere differences in single-word noun and verb recognition, these may be attributable to semantic dimensions that tend to covary with grammatical class.

Does global context modulate cerebral asymmetries? A review and new evidence on word imageability effects.

In this article we examine whether the distribution of function across the right and left cerebral hemispheres for lexical processing is influenced by the global context within which words are presented. A review of previously published studies indicates that the ubiquitous right visual field (RVF)/left hemisphere advantage for word recognition may be reduced or eliminated for nouns, content words, or high image words, but only when such items are presented along with verbs, function words, or low image words. However, paradoxically, when the former items are presented in more homogeneous contexts, the RVF advantage is uniformly observed. We propose that the processing efficiency of a hemisphere for a given stimulus depends on that items relation to the other stimuli provided, that is, the global context. This was examined in a visual half-field experiment that varied whether high and low image nouns were presented in homogeneous (blocked lists) or heterogeneous (mixed lists) contexts. An unvarying RVF advantage was observed for high image words in homogeneous contexts, but this advantage was eliminated when the same items were presented in heterogeneous contexts. We suggest that stimulus heterogeneity maximizes reliance on differing, but complementary, computational biases across hemispheres. Hence, the extent to which the left and right hemispheres are recruited for the recognition of individual word types can vary dynamically with variation in the stimulus environment.

No go on neutrals? An interhemispheric account of semantic category priming

In a divided-visual-field priming paradigm, participants made manual lexical decisions performing either go no-go responses, or yes-no responses, to related prime-target word pairs that were nonassociated, category members (DEER-PONY). Half of each response group received unrelated (ATTIC-PONY) baselines and half received neutral (BLANK-PONY) baselines. In the go no-go response, small but reliable priming was obtained in both target visual fields and there was a reliable slowing of response time in the right visual field/left hemisphere for participants receiving the neutral baseline. In the yes-no response, greater priming was obtained from a neutral baseline, as compared to an unrelated baseline. We show that under appropriate conditions priming for these stimuli occurs in both visual fields. We also report that cross-visual-field advantages emerged as cognitive task load increased across combinations of baseline and response variables. We conclude that task load may be as important a factor in priming asymmetries as SOA or type of semantic relationship.

Exploring cerebral asymmetries for the verb generation task.

This study investigated potential right hemisphere involvement in the verb generation task. Six divided visual field experiments explored cerebral asymmetries for word retrieval in the verb generation task as well as in rhyme generation and immediate and delayed word pronunciation. The typical right visual field/left hemisphere (RVF/LH) advantage was observed for pronunciation and rhyme generation. For verb generation, the RVF/LH advantage was obtained only when stimulus items had a single prepotent response and not when there were multiple response alternatives. A semantic priming experiment suggested that activation for less common, related verbs was maintained for a longer time course within the right than within the left hemisphere. The authors suggest that the right hemisphere may play a role in continued activation of semantically related response alternatives in word generation and discuss methodological implications of their findings.

Influence of word class proportion on cerebral asymmetries for high- and low-imagery words

It has been claimed that the typical RVF/LH advantage for word recognition is reduced or eliminated for imageable, as compared to nonimageable, nouns. To determine whether such word-class effects vary depending on the stimulus list context in which the words are presented, we varied the proportion of high- and low-image words presented in a lateralized lexical decision task (0, 25, 50, 75, or 100% high image). Although the RVF/LH advantage for high-image words was unaltered by word-class proportion, a significant linear trend was obtained for the low-image words such that the RVF/LH advantage increased as the proportion of low-image words increased. We discuss the implications of these findings for models of how lexical processing is distributed across hemispheres.

Knowledge-Based Inferences Are Not General.

Although knowledge-based inferences (Graesser, Singer, & Trabasso, 1994) depend on general knowledge, there may be differences across knowledge areas in how they support these processes. This study explored processing differences between 2 areas of knowledge (physical cause–effect vs. goals and planning) to establish (a) that each would support knowledge-based inferences and (b) that differences in knowledge areas, but not inference abilities, would impact comprehension after acquired brain injury (ABI). ABI participants were compared to matched noninjured participants (NI). The hypothesis was that ABI participants would make physical, but not planning, inferences. NI participants were expected to make inferences from both knowledge areas. Participants read 2-sentence texts and provided measures of inference processes by probe recognitions and knowledge-validating questions. NI participants demonstrated equal inference processes across knowledge areas. ABI participants demonstrated inferences primarily for physical knowledge, indicating that inference processes were intact, yet were less available from planning knowledge. These data support the dissociation of physical cause and effect from planning knowledge, consistent with causal reasoning theory (Trabasso, van den Broek, & Suh, 1989). Further, these findings suggest that areas of general knowledge may differentially support the inference processes involved in comprehension.

Cognitive Demand Differences in Causal Inferences: Characters' Plans are More Difficult to Comprehend Than Physical Causation

Readers may draw knowledge-based inferences to connect sentences in text differently depending on the knowledge domain being accessed. Most prior research has focused on the direction of the causal explanation (predictive vs. backward) without regard to the knowledge domain drawn on to support comprehension. We suggest that less cognitive effort is required for physical cause-and-effect inferences than for inferences drawn from goal-directed or planning knowledge. Using a dual task that required readers to hold word lists in memory while reading simple texts, we measured inference processes across knowledge areas by probe word recognitions and knowledge-validating questions. In Experiment 1 a word-recall task of 3 versus 6 items was employed to overload working memory and attention. In Experiment 2, a no-load level was included for comparison. The impact of cognitive loads (high vs. low vs. no) was expected to impair inference processes more for planning than physical knowledge, which our results supported. These findings suggest that demands on cognitive resources, which support inference processes, vary by knowledge domain. Findings also indicate that answering questions is more demanding than probe recognitions. These findings are informative to cognitive retraining programs for survivors of acquired brain injury, indicating that knowledge domains requiring less cognitive resources may be more accessible.

Text-Speak processing:

There has been a steady shift from more traditional means of communication (e.g., hand written letters) to more electronically based (e.g., text messaging) (Crystal, 2008). This shift in communication style has influenced both civilian and military occupations (Turkoski, 2009; Finomore, et al., 2010). The current study investigated whether text-speak (method for shortening words or phrases) provides semantic value. A text-speak proficiency scale was also created in order to determine if the extent of text-speak use correlates with behavioral performance. Eighty-seven university students completed a masked priming experiment coupled with an 8-item text-speak scale. The masked priming experiment yielded significant priming indicating that text-speak primes are semantically meaningful, because they facilitate responding to their word counterpart even when the prime is processed unconsciously. The 8-item scale yielded a correlation between willingness to use text speak and magnitude of priming. These findings suggest that the 8-item scale may be useful in assessing text-speak behavior and aid in a better understanding of the role of text