Semantic interference in picture naming during dual-task performance does not vary with reading ability

Previous dual-task studies examining the locus of semantic interference of distractor words in picture naming have obtained diverging results. In these studies, participants manually responded to tones and named pictures while ignoring distractor words (picture–word interference, PWI) with varying stimulus onset asynchrony (SOA) between tone and PWI stimulus. Whereas some studies observed no semantic interference at short SOAs, other studies observed effects of similar magnitude at short and long SOAs. The absence of semantic interference in some studies may perhaps be due to better reading skill of participants in these than in the other studies. According to such a reading-ability account, participants’ reading skill should be predictive of the magnitude of their interference effect at short SOAs. To test this account, we conducted a dual-task study with tone discrimination and PWI tasks and measured participants’ reading ability. The semantic interference effect was of similar magnitude at both short and long SOAs. Participants’ reading ability was predictive of their naming speed but not of their semantic interference effect, contrary to the reading ability account. We conclude that the magnitude of semantic interference in picture naming during dual-task performance does not depend on reading skill.     

Getting connected: Both associative and semantic links structure semantic memory for newly learned persons

The present study examined whether semantic memory for newly learned people is structured by visual co-occurrence, shared semantics, or both. Participants were trained with pairs of simultaneously presented (i.e., co-occurring) preexperimentally unfamiliar faces, which either did or did not share additionally provided semantic information (occupation, place of living, etc.). Semantic information could also be shared between faces that did not co-occur. A subsequent priming experiment revealed faster responses for both co-occurrence/no shared semantics and no co-occurrence/shared semantics conditions, than for an unrelated condition. Strikingly, priming was strongest in the co-occurrence/shared semantics condition, suggesting additive effects of these factors. Additional analysis of event-related brain potentials yielded priming in the N400 component only for combined effects of visual co-occurrence and shared semantics, with more positive amplitudes in this than in the unrelated condition. Overall, these findings suggest that both semantic relatedness and visual co-occurrence are important when novel information is integrated into person-related semantic memory.     

Are there qualitative differences in the representation of abstract and concrete words? Within-language and cross-language evidence from the semantic priming paradigm

The different organizational frameworks theory proposes that there is a qualitative difference between the representation of concrete and abstract words in memory: Concrete concepts would be primarily organized in terms of semantic similarity whereas abstract concepts would be mainly organized by their association with other concepts. Evidence in support of this proposal has been mostly obtained with neuropsychological populations and, to a lesser extent, with healthy participants. In the present work, we tested the different organizational frameworks theory by using, for the first time, a semantic priming paradigm both within language and across languages. The results revealed that there was priming for both semantically similar and associative relations when words were concrete. However, with abstract words, priming was only observed when pairs and targets were associated. These results do not support the proposal of Crutch and coworkers, suggesting that the experimental paradigm as well as the type of relations tested may modulate the pattern of effects obtained with concrete and abstract words.     

Disengaging the negative priming mechanism in location tasks

In a location-based negative priming task, targets that appear at locations that were previously occupied by distractors are typically responded to more slowly than are targets that appear at formerly unoccupied positions. In the present study, we attempted to disengage the location-based negative priming mechanism by presenting visual cues indicating the most likely location of the upcoming target. The first experiment showed that 75% cue-target validity was not sufficient to affect the negative priming mechanism. However, the second experiment demonstrated that a much reduced, but not eliminated, negative priming effect occurred with 100%cue-target validity. These findings are similar to those found with inhibition of return, suggesting that location-based inhibition of return effects and location-based negative priming effects may share a common inhibition mechanism.     

Is phonological short-term memory related to phonological analysis stages in auditory sentence processing?

Despite extensive research, the role of phonological short-term memory (STM) during oral sentence comprehension remains unclear. We tested the hypothesis that phonological STM is involved in phonological analysis stages of the incoming words, but not in sentence comprehension per se. We compared phonological STM capacity and processing times for natural sentences and sentences containing phonetically ambiguous words. The sentences were presented for an auditory sentence anomaly judgement task and processing times for each word were measured. STM was measured via nonword and word immediate serial recall tasks, indexing phonological and lexicosemantic STM capacity, respectively. Significantly increased processing times were observed for phonetically ambiguous words, relative to natural stimuli in same sentence positions. Phonological STM capacity correlated with the size of this phonetic ambiguity effect. However, phonological STM capacity did not correlate with measures of later semantic integration processes while lexicosemantic STM did. This study suggests that phonological STM is associated with phonological analysis processes during sentence processing.     

Sampling the process of autobiographical memory construction

In three autobiographical memory retrieval experiments participants reported the contents of consciousness to a probe presented at early and late points during retrieval. Classification of the protocols according to the specificity of the reported knowledge found that early in retrieval abstract knowledge predominated whereas at the later point, close to generation or formation of a memory, knowledge related to specific events was more frequent. For some memories very fast and full retrieval was observed at the early point and this was independent of other concurrent processing demands. These findings show that generative retrieval entails iterative access of autobiographical knowledge but this is not observed in direct retrieval.     

Inhibition from blinked category labels: Combining the attentional blink and the semantic priming paradigm

In the present experiment we combined the attentional blink and the semantic priming paradigm. We used category labels as primes and category exemplars as targets. The prime stimuli were embedded into a rapid serial visual presentation (RSVP) stream and presented at varying positions after a to-be-identified stimulus, albeit the stimulus–onset asynchrony between primes and targets remained constant throughout the experiment. As a result, participants’ prime awareness was reduced in some trials although the prime duration was always at levels usually considered to elicit awareness (60 ms). After each RSVP there was a forced choice discrimination test to assess participants’ prime awareness. When subjects could not identify the prime stimuli we observed slower responses to related as compared to unrelated targets. This result confirms results found with repeated masked primes. However, whereas former studies assessed unawareness rather coarsely at the level of individual participants, here unawareness was tested on a trial-by-trial basis.     

Posture recognition in Alzheimer's disease

BACKGROUND: Apraxia is neurologically induced deficit in the ability perform purposeful skilled movements. One of the most common forms is ideomotor apraxia (IMA) where spatial and temporal production errors are most prevalent. IMA can be associated Alzheimer's disease (AD), even early in its course, but is often not identified possibly because the evaluation of IMA by inexperienced judges using performance tests is unreliable. The purpose of this study, therefore, is to learn if the Postural Knowledge Test (PKT), a praxis discrimination test that assesses knowledge of transitive (PKT-T subtest) and intransitive (PKT-I subtest) postures and does not require extensive training, is as sensitive and specific as the praxis performance tests. METHODS: We studied 15 subjects with probable AD as well as 18 age-matched controls by having them perform transitive and intransitive gestures to command and imitation, as well as having them discriminate between correct and incorrect transitive and intransitive postures. RESULTS: Overall on all tests, the control subjects performed better than those with AD. In addition all subjects had more trouble with transitive than intransitive gestures. Using a stepwise discriminative analysis, 81.8% of the subjects could be classified according to Group (94.4% of Controls, 66.7% of AD subjects). In this analysis, the PKT-T (transitive posture subtest) was the only measure that contributed to the discrimination of subjects. CONCLUSION: We found that having subjects select the correct transitive hand postures in this "booklet test" was more sensitive than grading their praxis performances even when using judges with extensive training. This suggests that this discrimination test might be an excellent means for diagnosing and screening patients for AD. The reason why recognition of transitive postures is relatively more difficult for our AD subjects is not known. Two possibilities are that the representations for intransitive movements are stronger than those for transitive movements, and hence, more resistant to degradation, or that intransitive acts are stored in parts of the brain not affected by AD.     

Ideational action impairments in Alzheimer's disease

We report data from a group of patients with mild Alzheimer's disease on a range of tasks requiring either stored semantic knowledge about objects (e.g., naming object use) or the execution of action to objects (e.g., miming and using objects). We found that the patients were impaired at miming in response to objects, even when they could describe the object's function. On the other hand, copying gestures was not impaired relative to naming gestures, indicating that an ideomotor deficit in action execution, per se, was unlikely to explain the impairments in object use. We suggest instead that the patients had an impairment in stored motor programmes for action, over and above their deficits in semantic knowledge. Despite this, the patients were better at using than at miming to objects, consistent with the view that proprioceptive input (when using objects) can directly constrain selection of the appropriate motor programme for action.