Dual-coding, context-availability, and concreteness effects in sentence comprehension: an electrophysiological investigation.

Event-related potentials were recorded in 2 experiments while participants read sentences in a word-by-word congruency judgment task. Sentence final words were either congruent, semantically anomalous (Experiments 1 and 2), or neutral (Experiment 2) with respect to sentence context. Half of all final words referred to concrete and half to abstract concepts. A different scalp distribution of the N400 to concrete and abstract final words was found for anomalous and neutral, but not congruent sentences. Although the interaction of context and concreteness is consistent with the context-availability model, the differential scalp distribution of effects for concrete and abstract words, as well as larger context effects for concrete words, was interpreted as being more consistent with an extended dual-code account of semantic processing.     

The time course of orthographic and phonological code activation

The present study used event-related potentials (ERPs) to examine the time course of orthographic and phonological priming in the masked priming paradigm. Participants monitored visual target words for occasional animal names, and ERPs to nonanimal critical items were recorded. These critical items were preceded by different types of primes: Orthographic priming was examined using transposed-letter (TL) primes (e.g., barin-BRAIN) and their controls (e.g., bosin-BRAIN); phonological priming was examined using pseudohomophone primes (e.g., brane-BRAIN) and their controls (e.g., brant-BRAIN). Both manipulations modulated the N250 ERP component, which is hypothesized to reflect sublexical processing during visual word recognition. Orthographic (TL) priming and phonological (pseudohomophone) priming were found to have distinct topographical distributions and different timing, with orthographic effects arising earlier than phonological effects.     

Primed picture naming within and across languages: An ERP investigation

In two experiments, while event-related potentials (ERPs) were recorded, participants named picture targets that were preceded by masked word primes that corresponded either to the name of the picture target or to an unrelated picture name. Experiment 1 showed significant priming effects in the ERP waveforms, free from articulator artifact, starting as early as 200 msec post target onset. Possible loci of these priming effects were proposed within the framework of generic interactive activation models of word recognition and picture naming. These were grouped into three main components: object-specific structural representations, amodal semantic representations, and word-specific phonological and articulatory representations. Experiment 2 provided an initial test of the possible role of each of these components by comparing within-language repetition priming with priming from translation equivalents in bilingual participants. The early and widespread effects of noncognate translation primes in L1 on picture naming in L2 point to object-specific and amodal semantic representations as the principal loci of priming effects obtained with masked word primes and picture targets.     

Toward a behavioral analysis of joint attention

Joint attention (JA) initiation is defined in cognitive-developmental psychology as a child's actions that verify or produce simultaneous attending by that child and an adult to some object or event in the environment so that both may experience the object or event together. This paper presents a contingency analysis of gaze shift in JA initiation. The analysis describes reinforcer-establishing and evocative effects of antecedent objects or events, discriminative and conditioned reinforcing functions of stimuli generated by adult behavior, and socially mediated reinforcers that may maintain JA behavior. A functional analysis of JA may describe multiple operant classes. The paper concludes with a discussion of JA deficits in children with autism spectrum disorders and suggestions for research and treatment.     

An electrophysiological investigation of the effects of coreference on word repetition and synonymy

In two experiments the effects of word repetition, synonymy, and coreference on event-related brain potentials during text processing were studied. Participants read one (Experiment 1) or two sentence (Experiment 2) texts in which critical nouns were preceded by the definite (the) or indefinite (a) articles. Experiment 1 was run as a control to verify that differences in article processing in the second sentences of Experiment 2 would not contaminate the ERPs to critical noun items. They did not. In Experiment 2, an initial sentence was used to set up a context and contained either a first presentation or synonym of the critical word from the second sentence. N400 (but not Late Positive Component; LPC) priming effects were found for repetitions and synonyms (larger for repetitions) in second sentences. This extends observations of priming in word lists and single sentences to two-sentence texts. There was also a greater left anterior negativity or "LAN" for coreferential critical nouns (those following the article "The") compared to non-coreferential critical nouns (those following the article "A") suggesting that ERPs are sensitive to working memory processes engaged during referential assignment. In response to the articles themselves, there was a greater N400-700 elicited by the article "A" vs. "The." Finally, there was a greater N400-like negativity to the final words of non-coreferential sentences implying that the meanings of these sentences were difficult to integrate with the discourse level representation established by the prior sentence.     

Structure and process in semantic memory: evidence from event-related brain potentials and reaction times.

Through scalp measurements of the electrical activity of the brain (event-related potentials, or ERPs) recorded while subjects verified the truth of sentences relating exemplars and categories (e.g., ALL DOGS ARE ANIMALS), inferences were made about aspects of semantic processing that were not directly reflected by overt responses. In particular, it is suggested that a negative ERP component that peaks about 400 ms after the onset of the sentence predicate (i.e., N400) is sensitive to structural aspects of semantic memory. The amplitude of this component was modulated by the relatedness of the subject and predicate terms, as well as the hierarchical level of both these terms, but was not sensitive to the truth value of a sentence.     

Autonomic responsivity during visual search of hyperactive and reading-disabled children

Heart rate and skin conductance measures, recorded during a visual search task, were compared for hyperactive, reading-disabled, hyperactive reading-disabled, and control elementary school boys. As shown in past work, basal autonomic levels did not statistically differentiate groups. In all groups, heart rate levels increased with task complexity, but more so on reward than on nonreward trials. In the intertriai interval, heart rate decelerated consistently when subjects were anticipating stimuli associated with reward, but when reward was uncertain, heart rate accelerated slightly or stayed the same. Control subjects exhibited anticipatory heart rate deceleration more consistently than did clinical subjects, especially the solely hyperactive ones. Skin conductance levels first decreased, then rose as task complexity increased, but the groups did not differ on this measure. A conditioning model is outlined to explain directional changes in heart rate.     

Homicide without an apparent motive

Fifty-two defendants who allegedly killed without apparent motive were compared to 154 homicide defendants with clear motives on demographic and psychiatric variables. Individuals who killed without motive were more likely to have: (1) no history of alcohol abuse: (2) a recent release from prison: (3) claims of amnesia for the crime; and (4) denial of the crime. They also tended to exhibit psychotic behavior following the crime and to be assessed as not guilty of the crime due to mental illness.     

Code-switching effects in bilingual word recognition: a masked priming study with event-related potentials

Two experiments tested language switching effects with bilingual participants in a priming paradigm with masked primes (duration of 50 ms in Experiment 1 and 100 ms in Experiment 2). Participants had to monitor target words for animal names, and ERPs were recorded to critical (non-animal) words in L1 and L2 primed by unrelated words from the same or the other language. Both experiments revealed language priming (switching) effects that depended on target language. For target words in L1, most of the language switch effect appeared in the N400 ERP component, with L2 primes generating a more negative going wave than L1 primes. For L2 target words, on the other hand, the effects of a language switch appeared mainly in an earlier ERP component (N250) peaking at approximately 250 ms post-target onset, and showing greater negativity following an L1 prime than an L2 prime. This is the first evidence for fast-acting language-switching effects occurring in the absence of overt task switching.     

An ERP investigation of location invariance in masked repetition priming

In an experiment combining masked repetition priming and the recording of event-related potentials (ERPs) the location of prime stimuli relative to centrally located target words was manipulated. Prime words could appear at the same location as targets or shifted one letter position to the right or to the left. Repetition priming effects (amplitude differences across the repeat vs. unrelated prime conditions) were found in a series of ERP components starting at around 100 msec posttarget onset. The earliest of these, the N/P150 component, was found to be sensitive to prime location. Repetition priming was only apparent with centrally located primes in this component. Repetition priming effects in later components (N250 and N400), on the other hand, were not affected by prime location. The results are interpreted in terms of location-specific letter detectors that map onto a higher level, location-invariant orthographic code for printed words.