Semantic Blocking Research Articles

Temporal characteristics of semantic perseverations induced by blocked-cyclic picture naming

When unimpaired participants name pictures quickly, they produce many perseverations that bear a semantic relation to the target, especially when the pictures are blocked by category. Evidence suggests that the temporal properties of these “semantic perseverations” may differ from typical lexical perseverations in aphasia. To explore this, we studied semantic perseverations generated by participants with aphasia on a naming task with semantic blocking [Schnur, T. T., Schwartz, M. F., Brecher, A., & Hodgson, C. (2006). Semantic interference during blocked-cyclic naming: Evidence from aphasia. Journal of Memory and Language, 54, 199–227]. The properties of these perseverations were investigated by analyzing how often they occurred at each lag (distance from prior occurrence) and how time (response-stimulus interval) influenced the lag function. Chance data sets were created by re-shuffling stimulus-response pairs in a manner that preserved unique features of the blocking design. We found that the semantic blocking manipulation did not eliminate the expected bias for short-lag perseverations (recency bias). However, immediate (lag 1) perseverations were not invariably the most frequent, which hints at a source of inconsistency within and across studies. Importantly, there was not a reliable difference between the lag functions for perseverations generated with a 5 s, compared to 1 s, response-stimulus interval. The combination of recency bias and insensitivity to elapsed time indicates that the perseveratory impetus in a named response does not passively decay with time but rather is diminished by interference from related trials. We offer an incremental learning account of these findings.

Consequences of an inhibition deficit for word production and comprehension: Evidence from the semantic blocking paradigm

We investigated the semantic blocking effect in picture naming and word–picture matching for two nonfluent aphasic patients who show evidence of a deficit in inhibiting verbal representations (M.L. and B.Q.), one fluent aphasic patient (K.V.), and neurologically intact control participants. In two picture-naming tasks (Experiments 1A and 1B), M.L. and B.Q., relative to controls, showed a greatly exaggerated semantic blocking effect in naming latencies that increased dramatically across repeated presentations. On two corresponding word–picture matching tasks (Experiments 2A and 2B), both also showed an increasing semantic blocking effect, though the effects were not as large nor as consistent as those in naming. The fluent patient, K.V., showed a pattern like controls on both tasks. On an associated word–picture matching task, both M.L. and B.Q. showed results paralleling those of controls. The contrast between the production and comprehension patterns for M.L. and B.Q. supports the conclusion that their exaggerated blocking effect in production arises during lexical rather than semantic selection. We postulate that M.L.'s (and potentially B.Q.'s) production effect is due to difficulties in postselection inhibition, which results in overactivation of lexical representations. This overactivation is likely to be one source of their nonfluency in spontaneous speech.

Effects of working memory load on lexical-semantic encoding in language production

Some models of lexical access in language production postulate that lexical-semantic encoding is driven bottom-up, by the conceptual input, and top-down, by a representation of the task. In the cyclic semantic blocking paradigm, participants repeatedly name sets of objects that are either semantically related or unrelated. Whereas the manipulation of semantic relatedness affects lexical-semantic encoding in a bottom-up fashion, the cyclic presentation of small object sets allows participants to bias the corresponding lexical-semantic representations top-down for selection. The role of working memory (WM) in this top-down modulation was investigated by crossing the cyclic semantic blocking paradigm with a manipulation of WM load. Participants' naming latencies displayed significant effects of semantic context, WM load, and their interaction. A word-naming task using the same materials yielded a main effect of WM load but no significant effects of semantic context or of its interaction with WM load. These and related results are discussed with regard to their implications for models of language production.

Regulatory functions of prefrontal cortex during single word production

Over the past decade, many neuropsychological and neuroimaging studies have investigated the putative linguistic and nonlinguistic functions of prefrontal cortex, specifically the posterior portion of the left, inferior frontal gyrus (LIFG) also known as ‘‘Broca’s area’’. A number of these studies have converged on the hypothesis that LIFG functions to regulate activation among competing representations across a wide variety of linguistic (and nonlinguistic) situations (e.g., Robinson, Blair, & Cipolotti, 1998; Thompson-Schill, D’Esposito, & Kan, 1999). This hypothesis draws on a large body of research into the function of prefrontal cortex (e.g., Miller & Cohen, 2001), and contrasts with other more domain-specific accounts of the function of Broca’s area. Here, we present both functional neuroimaging data from young, healthy volunteers and lesion-deficit analyses of patients with focal brain damage that jointly provide support for the regulatory hypothesis of LIFG involvement in language processing, and that more broadly inform the study of both linguistic and nonlinguistic cognitive processes. In several prior studies (e.g., Kan & Thompson-Schill, 2004), we manipulated competition during single word production across items, by systematically varying intersubject name agreement (e.g., a picture of a banana, which is consistently named as such, versus a picture of a shirt, which is alternatively named as a blouse, a top, a jacket). Activation in LIFG—and errors made by a patient with focal damage to this region—increased during naming of pictures with many, compared to few, competing names. Although these findings are consistent with the hypothesized regulatory role of LIFG in word production, differences across items are subject to a number of alternative interpretations. In the present series of experiments, we manipulated competition during single word production within items, taking advantage of a robust interference effect on picture naming that results from semantic blocking: Repeated naming of a group of pictures drawn from a common semantic category is slower (and in patients with aphasia, more error-prone) than is repeated naming of the same pictures arranged in unrelated blcoks (e.g., Damian, Vigliocco, & Levelt, 2001; Schnur, Schwartz, Brecher, & Hodgson, 2006). We (and others) have argued that this semantic blocking manipulation increases competition among semantically related items, and thereby increases demands for a regulatory (control) process that is hypothesized to require the LIFG. In the first experiment, fMRI data were collected while sixteen subjects named line drawings of common objects. Half of the picture naming blocks comprised repeated sets of unrelated pictures. The other half of the picture naming blocks comprised repeated sets of either semantically-related pictures (i.e., same category) or phonologically-related pictures (i.e., names with same onset). Comparisons of semantically-related blocks to unrelated blocks revealed increased activation in LIFG, t(15) = 2.37, p < .05 and left temporal cortex, t(15) = 2.14, p < .05; however, only the former was correlated with behavioral performance, r = .76. Furthermore, the effect of semantic blocking was greater than the (null) effect of phonological blocking – which is typically associated with facilitation, not interference—only in the LIFG, t(15) = 2.21, p < .05. In the second experiment, we analyzed error rates of twelve chronically aphasic patients attempting to repeatedly name pictures appearing in semantically related or unrelated blocks. We obtained high-resolution MRI or CT scans in order to perform a number of analyses relating structural abnormalities to functional impairments. First, in a region of interest analysis, we found that patients who exhibited a large blocking effect had more substantial LIFG damage than did patients who exhibited a small (or absent) blocking effect, t(10) = 3.59, p < .01. (In this and subsequent analysis, the magnitude of the blocking effect was described by a measure of the interaction between semantic blocking and repetition on error rates.) Second, we conducted a whole-brain analysis, comparing the magnitude of the blocking effect as a function of tissue status (damaged versus intact) at every voxel in the brain. In aggregate, lesions from the twelve

Motivation and semantic context affect brain error-monitoring activity: An event-related brain potentials study

During speech production, we continuously monitor what we say. In situations in which speech errors potentially have more severe consequences, e.g. during a public presentation, our verbal self-monitoring system may pay special attention to prevent errors than in situations in which speech errors are more acceptable, such as a casual conversation. In an event-related potential study, we investigated whether or not motivation affected participants’ performance using a picture naming task in a semantic blocking paradigm. Semantic context of to-be-named pictures was manipulated; blocks were semantically related (e.g., cat, dog, horse, etc.) or semantically unrelated (e.g., cat, table, flute, etc.). Motivation was manipulated independently by monetary reward. The motivation manipulation did not affect error rate during picture naming. However, the high-motivation condition yielded increased amplitude and latency values of the error-related negativity (ERN) compared to the low-motivation condition, presumably indicating higher monitoring activity. Furthermore, participants showed semantic interference effects in reaction times and error rates. The ERN amplitude was also larger during semantically related than unrelated blocks, presumably indicating that semantic relatedness induces more conflict between possible verbal responses.

When bees hamper the production of honey: Lexical interference from associates in speech production.

In this article, the authors explore semantic context effects in speaking. In particular, the authors investigate a marked discrepancy between categorically and associatively induced effects; only categorical relationships have been reported to cause interference in object naming. In Experiments 1 and 2, a variant of the semantic blocking paradigm was used to induce two different types of semantic context effects. Pictures were either named in the context of categorically related objects (e.g., animals: bee, cow, fish) or in the context of associatively related objects from different semantic categories (e.g., apiary: bee, honey, bee keeper). Semantic interference effects were observed in both conditions, relative to an unrelated context. Experiment 3 replicated the classic effects of categorical interference and associative facilitation in a picture-word interference paradigm with the material used in Experiment 2. These findings suggest that associates are active lexical competitors and that the microstructure of lexicalization is highly flexible and adjustable to the semantic context in which the utterance takes place.

Activation vs. inhibition accounts of semantic blocking effects in production and comprehension

Activation vs. inhibition accounts of semantic blocking effects in production and comprehension

Semantic interference during blocked-cyclic naming: Evidence from aphasia

Nonaphasic speakers are known to take longer to name pictures when they are blocked by semantic category and repeated multiple times. We replicated this “semantic blocking effect” in older controls and showed that in aphasia, the effect is manifested in increased error rates when naming semantically homogeneous, compared to mixed blocks. We further showed that semantic blocking affects Broca’s aphasics more than a matched group of NonBrocas, and that the effect increases with repetition of the blocked sets. Error analysis undermines the inhibition-based account of the blocking effect by showing that errors arise from competition among increasingly activated items within the homogeneous set. The consequent slowing of naming latencies is due at least in part to the intervention of a controlled selection mechanism, and the disruption of this mechanism in anterior aphasia accounts for the increase in error vulnerability.

Implicit and explicit processing in deep dyslexia: Semantic blocking as a test for failure of inhibition in the phonological output lexicon

The failure of inhibition hypothesis posits a theoretical distinction between implicit and explicit access in deep dyslexia. Specifically, the effects of failure of inhibition are assumed only in conditions that have an explicit selection requirement in the context of production (i.e., aloud reading). In contrast, the failure of inhibition hypothesis proposes that implicit processing and explicit access to semantic information without production demands are intact in deep dyslexia. Evidence for intact implicit and explicit access requires that performance in deep dyslexia parallels that observed in neurologically intact participants on tasks based on implicit and explicit processes. In other words, deep dyslexics should produce normal effects in conditions with implicit task demands (i.e., lexical decision) and on tasks based on explicit access without production (i.e., forced choice semantic decisions) because failure of inhibition does not impact the availability of lexical information, only explicit retrieval in the context of production. This research examined the distinction between implicit and explicit processes in deep dyslexia using semantic blocking in lexical decision and forced choice semantic decisions as a test for the failure of inhibition hypothesis. The results of the semantic blocking paradigm support the distinction between implicit and explicit processing and provide evidence for failure of inhibition as an explanation for semantic errors in deep dyslexia.

When lexical selection gets tough, the LIFG gets going: A lesion analysis study of interference during word production

Nonaphasic speakers take longer to name a repeated series of pictures from the same semantic category vs. mixed categories, due to semantically mediated competition for lexical selection (Damian, Vigliocco, & Levelt, 2001). Thompson-Schill et al. (1998) argued that damage to the left inferior frontal gyrus (LIFG) compromises selection when competition is high. Consistent with this, anterior (Broca) aphasics showed a larger blocking effect (more errors in semantically homogeneous vs. mixed blocks) compared to posterior aphasics, and this effect linearly increased across repetitions (Schnur, Brecher, Rossi, & Schwartz, 2004). In this study, we analyzed high-resolution structural MRI and CT scans, collected from a subgroup of aphasics reported by Schnur et al., to directly examine the relationship between the LIFG and the semantic blocking effect.

Facilitation and interference in phonological blocked-cyclic naming

The semantic blocking effect refers to the detrimental effect on naming latencies (nonaphasic speakers; e.g., Damian, Vigliococco, & Levelt, 2001) and accuracy (aphasic speakers) when targets are blocked by semantic category, compared with mixed-category presentation. The effect is most reliable when blocked sets are repeated multiple times in succession (i.e., for multiple ‘‘cycles’’). Schnur, Brecher, Rossi, and Schwartz (2004) recently showed that anterior aphasics are particularly vulnerable to the semantic blocking effect, as indexed by error rate in blocked-cyclic naming. They argued that the increased difficulty exhibited by their Broca’s group, compared to a matched group of fluent aphasic speakers, Non-Broca’s, is consistent with the theory that the left inferior frontal lobe subserves selection during high competition (Thompson-Schill, et al., 1998). Less well understood is the effect of phonological blocking. For nonaphasic speakers, naming sets of phonologically related words generally facilitates latencies (e.g., Damian, 2003), but sometimes it has the opposite effect (O’Seaghdha & Marin, 2000). Phonemic cueing paradigms used with aphasic patients have also produced mixed results, with some patients responding favourably, whereas others do not (Croot, Patterson, & Hodges, 1999). The present study investigated phonological blocking in aphasic and nonaphasic speakers, using the blocked-cyclic naming paradigm.

Refractory effects in picture naming as assessed in a semantic blocking paradigm

In the cyclic semantic blocking paradigm participants repeatedly name sets of objects with semantically related names (homogeneous sets) or unrelated names (heterogeneous sets). The naming latencies are typically longer in related than in unrelated sets. In Experiment 1 we replicated this semantic blocking effect and demonstrated that the effect only arose after all objects of a set had been shown and named once. In Experiment 2, the objects of a set were presented simultaneously (instead of on successive trials). Evidence for semantic blocking was found in the naming latencies and in the gaze durations for the objects, which were longer in homogeneous than in heterogeneous sets. For the gaze-to-speech lag between the offset of gaze on an object and the onset of the articulation of its name, a repetition priming effect was obtained but no blocking effect. Experiment 3 showed that the blocking effect for speech onset latencies generalized to new, previously unnamed lexical items. We propose that the blocking effect is due to refractory behaviour in the semantic system.

Age of acquisition effects in picture naming: evidence for a lexical-semantic competition hypothesis

In many tasks the effects of frequency and age of acquisition (AoA) on reaction latencies are similar in size. However, in picture naming the AoA-effect is often significantly larger than expected on the basis of the frequency-effect. Previous explanations of this frequency-independent AoA-effect have attributed it to the organisation of the semantic system or to the way phonological word forms are stored in the mental lexicon. Using a semantic blocking paradigm, we show that semantic context effects on naming latencies are more pronounced for late-acquired than for early-acquired words. This interaction between AoA and naming context is likely to arise during lexical-semantic encoding, which we put forward as the locus for the frequency-independent AoA-effect.

Deep dyslexia and semantic errors: A test of the failure of inhibition hypothesis using a semantic blocking paradigm

Deep dyslexia is an acquired reading disorder that involves the production of semantic errors and the inability to read aloud nonwords successfully. Several explanations for this reading impairment posit multiple loci of damage to account for the various error types produced in deep dyslexia. In contrast, the failure of inhibition hypothesis suggests that damage in the phonological output lexicon alone can explain these errors. Specifically, this hypothesis proposes normal processing via orthographic and phonological reading routes, as well as an intact semantic system. However, slowed or reduced inhibitory connections result in the failure to suppress spuriously activated neighbours in the phonological output lexicon, where neighbourhood can be defined in terms of phonology, orthography, or semantics. Given a failure to inhibit semantically related candidates, semantic reading errors occur. Important to the test of this hypothesis is that it evolves several predictions that are contrary to performance observed in the normal population. In particular, semantic errors are predicted to be greater in conditions where words are blocked according to semantic category than in random presentations. In addition, a semantic interference effect is expected. The results of semantic blocking were consistent with these predictions and lend support to the failure of inhibition hypothesis.

Evidence for a context-sensitive word retrieval disorder in a case of nonfluent aphasia

We describe a patient (BM) with nonfluent aphasia who presents with sparse, fragmented spontaneous speech but normal or near-normal performance on standard naming tasks. However, more detailed investigation revealed some unusual features to BM's naming: On a task involving repeated naming of a small set of targets, his performance degenerated when the targets were semantically blocked, particularly at fast rates of presentation. This semantic blocking effect was not observed in an analogous wordpicture matching task. Also, it was not present on a task where a set of words had to be named repeatedly in a fixed, predictable sequence. Finally, a fluent aphasic patient who presented with a classic “output” anomia failed to show the semantic blocking and predictability effects. It is suggested that BM suffers from a context-sensitive word retrieval disorder. The disorder is attributed to a difficulty in modulating activation within the lexical network. Implications for nonfluent aphasia, as well as for models of lexical retrieval, are discussed.

Source Memory and Encoding Strategy in Normal Aging

Of the memory deficits associated with aging, elders are most impaired at attributing the source to remembered information. Additionally, aging is marked by a decrease in the use of encoding strategies that are thought to enhance the acquisition and retention of information. We examined how manipulating the encoding strategy during acquisition affected item and source memory in 32 young and 68 elderly participants. Elderly participants were dichotomized into young-old and old-old based upon the median age (74 years). Memory was assessed using Word List A from the California Verbal Learning Test (CVLT) and its alternate form. Encoding strategy was manipulated by semantic clustering. For the Blocked List, words were presented grouped into their semantic categories, whereas for the Unblocked List categories were intermixed within the list. Item and source memory judgments were made 20 minutes after the final CVLT recall trial and again one week later. Results revealed a disproportionate decline in source, compared to item memory in the two older groups. Semantic blocking enhanced item memory for the elders, but not for the young. The amount of semantic clustering performed by the elders showed a decline with age and was positively related to source performance. Results also suggest that subtle age-related changes in semantic knowledge may be related to declines in semantic clustering and memory performance.

Interpretive versus structural effects on semantic memory

The possibility that sentence information may be stored in an inferentially distant form was investigated. During acquisition, subjects heard proverbs, and along with each proverb either a repetition, grammatical transformation, parasyntactic paraphrase, or an unrelated control sentence. Prompted free recall of the proverbs was then solicited. Analyses of propositions and content words recalled revealed the superiority of the parasyntactic group. Also, no interaction between groups and proverb imagery level was evident. The groups effect was discussed in terms of three hypotheses: imagery, semantic blocking, and the use of a common conceptual (nonlinguistic) base. The latter hypothesis was best supported, suggesting that more abstract forms of sentence storage are possible than that reported by Bransford, Barclay and Franks (1972) and by Kintsch and Monk (1972) .