Semantic Locus Research Articles

Information about word class is both semantically and lexically represented: evidence from an advantage for verbs in two speakers with aphasia

ABSTRACT Background: There has been a debate over how a word’s syntactic class is represented in the mind. One model claims that information is represented solely at the semantic level while another account holds that syntactic class information could be represented both at a semantic and an independent lexical level. Methods: Two aphasic participants with a significant advantage for naming verbs in comparison to nouns took part in the investigation. They were assessed with several picture naming tests, two comprehension tests as well as an object naming test comparing animate and inanimate objects. Results: In one participant, the pronounced deficit for nouns resulted from a semantic impairment: there was a comparable dissociation in comprehension of words, a nonverbal semantic deficit, and performance was mainly affected by semantic variables (imageability; animacy). In the other participant, the difference between nouns and verbs arose from a lexical impairment since no comparable comprehension deficit was observed. In addition, performance was affected, mainly, by lexical variables (word frequency). Discussion: Results from one participant suggest a semantic locus of noun–verb differences and provide empirical support for a specific model of objects’ and actions’ semantic representations. In contrast, the other participant’s performance strongly suggests the word class effect to arise from a lexical impairment. Thus, the study provides support for two independent loci of noun–verb differences thereby contradicting one account’s strong claim that noun–verb differences arise solely from semantic impairments. The results also speak against recent cognitive accounts rejecting the idea of independent lexical representations.

AoA effects in reading aloud and lexical decision: Locating the (semantic) locus in terms of the number of backward semantic associations.

In the present study, we analyse data from the English Lexicon Project to assess the extent to which age of acquisition (AoA) effects on word processing stem from the number of semantic associations tied to a word. We show that the backward number of associates (bNoA; that is, the log transformed number of words that produce the target word in free association) is an important predictor of both lexical decision and reading aloud performance, and reduces the typical AoA effect as represented by subject ratings in both tasks. Although the AoA effect is reduced, it remains a significant predictor of performance above and beyond bNoA. We conclude that the semantic locus of AoA effects can be found in the number of backward connections to the word, and that the independent AoA effect is due to network plasticity. We discuss how computational models currently explain AoA effects, and how bNoA may affect their processing.

Common and specific loci of Stroop effects in vocal and manual tasks, revealed by event-related brain potentials and posthypnotic suggestions.

In the Stroop task color words are shown in various print colors. When print colors are named or classified with button presses, interference occurs if word meaning is color-incongruent and facilitation if it is congruent. Although the Stroop effects in vocal and manual task versions are similar, it is unclear whether the underlying mechanisms are equivalent. We addressed this question by (a) recording event-related brain potentials (ERPs), (b) manipulating the lexicality of neutral stimuli, and (c) giving posthypnotic suggestions (PHS) that written words would lose their meaning. The Stroop effect in the vocal version was twice its manual counterpart. PHS strongly reduced both effects by a similar amount, supporting a common semantic locus during reading. Task- and hypnosis-invariant lexicality effects for neutral words ruled out presemantic reading loci. Articulation-artifact corrected ERPs showed task-invariant Stroop effects in N400 amplitudes, supporting similar semantic loci. However, in the vocal task response-locked ERPs indicated a task-specific Stroop effect over left-inferior frontal and parietal scalp sites, suggesting interference during word production. Interestingly, PHS increased the N1 and decreased the N2 components in ERPs, regardless of congruency, indicating enhanced proactive executive control and diminished demands on conflict-monitoring, respectively. Stroop effects in the N400 were reduced by PHS, confirming their semantic locus. In conclusion, vocal and manual Stroop versions seem to share semantic loci of conflict. The bigger vocal Stroop effect may be attributable to additional loci during word production lexicon. Apparently, PHS diminish Stroop effects by enhancing proactive executive control over lexico-semantic conflicts. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Long-term interference at the semantic level: Evidence from blocked-cyclic picture matching.

Processing semantically related stimuli creates interference across various domains of cognition, including language and memory. In this study, we identify the locus and mechanism of interference when retrieving meanings associated with words and pictures. Subjects matched a probe stimulus (e.g., cat) to its associated target picture (e.g., yarn) from an array of unrelated pictures. Across trials, probes were either semantically related or unrelated. To test the locus of interference, we presented probes as either words or pictures. If semantic interference occurs at the stage common to both tasks, that is, access to semantic representations, then interference should occur in both probe presentation modalities. Results showed clear semantic interference effects independent of presentation modality and lexical frequency, confirming a semantic locus of interference in comprehension. To test the mechanism of interference, we repeated trials across 4 presentation cycles and manipulated the number of unrelated intervening trials (zero vs. two). We found that semantic interference was additive across cycles and survived 2 intervening trials, demonstrating interference to be long-lasting as opposed to short-lived. However, interference was smaller with zero versus 2 intervening trials, which we interpret to suggest that short-lived facilitation counteracted the long-lived interference. We propose that retrieving meanings associated with words/pictures from the same semantic category yields both interference due to long-lasting changes in connection strength between semantic representations (i.e., incremental learning) and facilitation caused by short-lived residual activation. (PsycINFO Database Record

Where are emotions in words? Functional localization of valence effects in visual word recognition.

Where are emotions in words? Functional localization of valence effects in visual word recognition.

Language can boost otherwise unseen objects into visual awareness.

Linguistic labels (e.g., "chair") seem to activate visual properties of the objects to which they refer. Here we investigated whether language-based activation of visual representations can affect the ability to simply detect the presence of an object. We used continuous flash suppression to suppress visual awareness of familiar objects while they were continuously presented to one eye. Participants made simple detection decisions, indicating whether they saw any image. Hearing a verbal label before the simple detection task changed performance relative to an uninformative cue baseline. Valid labels improved performance relative to no-label baseline trials. Invalid labels decreased performance. Labels affected both sensitivity (d') and response times. In addition, we found that the effectiveness of labels varied predictably as a function of the match between the shape of the stimulus and the shape denoted by the label. Together, the findings suggest that facilitated detection of invisible objects due to language occurs at a perceptual rather than semantic locus. We hypothesize that when information associated with verbal labels matches stimulus-driven activity, language can provide a boost to perception, propelling an otherwise invisible image into awareness.

Is handwriting constrained by phonology? Evidence from Stroop tasks with written responses and Chinese characters

To what extent is handwritten word production based on phonological codes? A few studies conducted in Western languages have recently provided evidence showing that phonology contributes to the retrieval of graphemic properties in written output tasks. Less is known about how orthographic production works in languages with non-alphabetic scripts such as written Chinese. We report a Stroop study in which Chinese participants wrote the color of characters on a digital graphic tablet; characters were either neutral, or homophonic to the target (congruent), or homophonic to an alternative (incongruent). Facilitation was found from congruent homophonic distractors, but only when the homophone shared the same tone with the target. This finding suggests a contribution of phonology to written word production. A second experiment served as a control experiment to exclude the possibility that the effect in Experiment 1 had an exclusively semantic locus. Overall, the findings offer new insight into the relative contribution of phonology to handwriting, particularly in non-Western languages.

Differential impacts of age of acquisition on letter and semantic fluency in Alzheimer's disease patients and healthy older adults

The degree to which the typical age of acquisition (AoA) of words and word frequency have separable influences on verbal production tasks has been strongly debated. To examine the overlap between these factors in verbal fluency tasks, the performance of Alzheimer's disease (AD) patients (N = 34) and normal elderly controls (N = 36) was compared on semantic (e.g., vegetables) and letter (e.g., words that begin with F) fluency tasks. These comparisons revealed that words generated for the semantic fluency task had an earlier AoA while words generated for the letter fluency task had a higher word frequency. Differences in AoA between AD patients and controls were larger for semantic than letter fluency. These results suggest that AoA has an effect on verbal production that is independent of word frequency and that AoA has a semantic locus.

A visual and semantic locus to beneficial effects of verbalization on face memory

We examined the effect of verbally describing a face on face memory as assessed in an old-new recognition task. Verbal facilitation, measured by a difference between verbalization and control conditions, was greater for upright than for inverted faces and greater for unfamiliar than for familiar faces. We propose that generating a verbal description enhances the processing of global visual information that differentiates an individual face from other faces that are encountered and also improves recognition through the association of visually derived semantic information. Verbalization enhances visual and semantic distinctiveness in memory.

Part-of-speech persistence: The influence of part-of-speech information on lexical processes

This paper presents three naming experiments designed to investigate whether the activation levels of syntactic features associated with lexical items, specifically part-of-speech information, can influence lexical processes. Naming preferences for orthographically ambiguous but phonologically distinct English nouns and verbs, such as convict (CONvict n vs. conVICT v) were compared. In Experiment 1, ambiguous target words were preceded by unambiguous noun, verb, and letter (control) primes. Experiments 2 and 3 were designed to distinguish whether the priming effects observed in Experiment 1 have a syntactic or a semantic locus. In all three experiments, we found an influence of the part-of-speech of the prime on speakers’ naming preferences for the target. The results support a model of the lexicon in which part-of-speech information can influence lexical processes.

Classic identity negative priming involves accessing semantic representations in the left anterior temporal cortex

Classic identity negative priming (NP) refers to the finding that when an object is ignored, subsequent naming responses to it are slower than when it has not been previously ignored (Tipper, S.P., 1985. The negative priming effect: inhibitory priming by ignored objects. Q. J. Exp. Psychol. 37A, 571–590). It is unclear whether this phenomenon arises due to the involvement of abstract semantic representations that the ignored object accesses automatically. Contemporary connectionist models propose a key role for the anterior temporal cortex in the representation of abstract semantic knowledge (e.g., McClelland, J.L., Rogers, T.T., 2003. The parallel distributed processing approach to semantic cognition. Nat. Rev. Neurosci. 4, 310–322), suggesting that this region should be involved during performance of the classic identity NP task if it involves semantic access. Using high-field (4 T) event-related functional magnetic resonance imaging, we observed increased BOLD responses in the left anterolateral temporal cortex including the temporal pole that was directly related to the magnitude of each individual’s NP effect, supporting a semantic locus. Additional signal increases were observed in the supplementary eye fields (SEF) and left inferior parietal lobule (IPL).

Age-of-acquisition effects in picture naming: Are they structural and/or semantic in nature?

Pictures having early acquired names are named faster than pictures having late acquired names. Age-of-acquisition (AoA) effects in picture naming are generally ascribed to lexical phonological representations, but alternative hypotheses state that they are located at the levels of semantic and/or object recognition. In Experiment 1, a semantic locus of AoA effects was tested. Participants performed both a picture naming task and a name–object verification task on the same items in two different sessions. AoA effects were reliable in picture naming latencies but not in name–object verification times. In Experiment 2, an object recognition task was used with the same items as employed in Experiment 1. Late acquired items were responded to faster than early acquired items. The findings do not support a semantic or a structural locus of AoA effects in picture naming.

Negative Priming with Numbers: No Evidence for a Semantic Locus

Selective attention has been studied extensively using the negative priming (NP) paradigm. An important issue regards the representational level at which NP occurs. We investigated this issue by using numbers as stimuli. Because numbers have a well-defined semantic organization, which can be clearly measured by means of the distance effect, they are very suitable for testing the assumption that NP is situated at a central semantic level. Four experiments are presented in which the numerical distance between prime distractor and probe target was manipulated. The task was magnitude comparison. Target and distractor were defined on the basis of colour. In Experiment 1, all numbers were presented in Arabic format; NP was observed only with identical prime distractor and probe target, and no distance-related NP was observed. This could not be explained by a decay of inhibition since in Experiment 2 similar results were obtained with a shortened response-to-stimulus interval. Experiment 3 showed that these observations also hold for numbers presented verbally. Nevertheless, a cross-notational experiment with Arabic prime and verbal probe (Experiment 4) revealed no NP whatsoever and excluded the possibility that the absence of distance-related negative priming was the result of a fine-tuned inhibitory mechanism operating at the semantic level. The results are considered in the light of current theories of negative priming.

Imageability and Ambiguity Effects in Speeded Naming: Convergence and Divergence.

A current area of controversy within the literature on visual word recognition concerns the extent to which semantic information influences the computation of phonology. Experiment 1 revealed that both the imageability effect and the ambiguity advantage seen in the speeded naming task are confined to words with atypical mappings between spelling and sound. Nonetheless, it is possible that either of these effects may arise from the operation of the direct rather than the semantic pathway. Experiment 2 therefore included nonword fillers in order to minimize semantic reliance during speeded naming. This manipulation removed the imageability effect, indicating a semantic locus, but the ambiguity advantage remained, suggesting a nonsemantic locus. These results are considered in the context of computational models that incorporate a semantic level of representation.

A category-specific advantage for numbers in verbal short-term memory: Evidence from semantic dementia

This study explored possible reasons for the striking difference between digit span and word span in patients with semantic dementia. Immediate serial recall (ISR) of number and non-number words was examined in four patients. For every case, the recall of single-digit numbers was normal whereas the recall of non-number words was impaired relative to controls. This difference extended to multi-digit numbers, and remained even when frequency, imageability, word length, set size and size of semantic category were matched for the numbers and words. The advantage for number words also applied to the patients’ reading performance. Previous studies have suggested that semantic memory plays a critical role in verbal short-term memory (STM) and reading: patients with semantic dementia show superior recall and reading of words that are still relatively well known compared to previously known but now semantically degraded words. Additional assessments suggested that this semantic locus was the basis of the patients’ category-specific advantage for numbers. Comprehension was considerably better for number than non-number words. Number knowledge may be relatively preserved in semantic dementia because the cortical atrophy underlying the condition typically spares the areas of the parietal lobes thought to be crucial in numerical cognition but involves the inferolateral temporal-lobes known to support general conceptual knowledge.

A Semantic Locus for Refractory Behaviour: Implications for Access Storage Distinctions and the Nature of Semantic Memory

A single case study is presented of a global aphasic patient, JM, who shows similar impairments to other patients in the literature classified as "access dysphasics": On auditory word-written word matching tasks, JM's performance is inconsistent, it declines over repetitions, and it is sensitive to presentation rate and to the semantic relatedness of distractors (Forde & Humphreys, 1995). The deleterious effects of stimulus repetition can be attributed to JM's access to semantic information becoming refractory following activation of a target word or object. This paper examines the locus of the refractoriness by comparing JM's performance on tasks requiring access to presemantic perceptual representations or to semantic information. When both words and pictures were used as stimuli, JM was unimpaired on tasks thought to tap presemantic representations, such as visual lexical decision and unusual views matching, but performance became refractory on tasks that required access to fine-grained semantic information about specific items (e.g. associative matching). In addition, we found that the refractoriness spread across modalities when the targets changed from pictures to words. We discuss the implication of these findings for understanding the underlying nature of semantic representations of words and objects, and for the access-storage distinction in neuropsychology.

Semantic ambiguity effects in word identification.

The influence of semantic ambiguity on word identification processes was explored in a series of word naming and lexical-decision experiments. There was no reliable ambiguity effect in 2 naming experiments, although an ambiguity advantage in lexical decision was obtained when orthographically legal nonwords were used. No ambiguity effect was found in iexical decision when orthographically illegal nonwords were used, implying a semantic locus for the ambiguity advantage. These results were simulated by using a distributed memory model that also produces the ambiguity disadvantage in gaze duration that has been obtained with a reading comprehension task. Ambiguity effects in the model arise from the model's attempt to activate multiple meanings of an ambiguous word in response to presentation of that word's orthographic pattern. Reasons for discrepancies in empirical results and implications for distributed memory models are considered. Any comprehensive theory of mental representation and process must accommodate the complex means by which concepts are communicated through language. Through the course of history, humans have developed tools of communication that facilitate the relaying of ideas and concepts, such as a writing system or orthography. This mapping of concepts to orthography is not entirely one to one, however, resulting in some words that correspond to multiple concepts, which are known as semantically ambiguous words. When reading text, the context provided by preceding words and sentences provides a means of disambiguating such words. As a result, we may not even notice the ambiguity in words that we are reading in context. If, on the other hand, semantically ambiguous words are presented in isolation, their alternative meanings are readily accessible, and thus their ambiguous nature is noticed. In the research reported in this article, we compare performance on semantically ambiguous words with that of semantically unambiguous words in isolated word identification tasks and describe simulations of the empirical effects within the framework of a distributed memory architecture (Masson, 1995). The effect of semantic ambiguity on isolated word identification has usually been determined by comparing performance on unambiguous words (which are associated with only one