Individual differences in the neural basis of causal inferencing

This study used fMRI to examine individual differences in the neural basis of causal inferencing. Participants with varying language skill levels, as indexed by scores on the vocabulary portion of the Nelson-Denny Reading Test, read four types of two-sentence passages in which causal relatedness (moderate and distant) and presence or absence of explicit clause connectives were orthogonally varied to manipulate coherence and cohesion during inference generation. Skilled readers showed better neural efficiency (less activation) during all context sentences and during all inference conditions. Increased activation in less-skilled readers was most extensively distributed in the right hemisphere (RH) homologues of left hemisphere (LH) language areas, especially in the most difficult passage types. Skilled readers also showed greater sensitivity to coherence (greater activation and synchronization in moderately related than distantly related passages) whereas less-skilled readers showed sensitivity to cohesion (greater activation and synchronization when clause connectives were present than when they were not). These finding support the hypothesis that skilled reading comprehension requires recruitment of the RH on an “as needed” basis. We describe the dynamic spillover hypothesis, a new theoretical framework that outlines the conditions under which RH language contributions are most likely evoked.     

Contribution of Peer Deviancy Training to the Early Development of Conduct Problems: Mediators and Moderators

Three variables were tested as moderators of the relationship between peer deviancy training and child antisocial behavior in a longitudinal study of 267 boys and girls from ages 5.3 to 9.3 years. Deviancy training was directly measured by observation of the discourse and play of children with same-gender classmates. Peer deviancy training was significantly related to multi-setting child antisocial behavior from ages 5.3 to 9.3 years. Child impulsivity, poor parental discipline, and peer rejection were all significant moderators of that relationship, even in the context of their direct association with trajectories of antisocial behavior and after controlling for deviant peer affiliation. These moderator effects appeared to be associated with children's increased sensitivity to peer modeling and reinforcement of deviant discourse and play. Not all children are equally affected by peer deviancy training, and an array of intervention strategies are described that may serve to protect children from deviant peer influence.     

Semantic control of eye movements in picture scanning during sentence-picture verification

The Weber fraction, (I + Δ)/I, was measured for pure tones which were I presented either homophasically or antiphasically. For both stimuli, the Weber fraction was measured as a function of changes in the level of the standard tone Iand in the phase angle of addition between a test tone and the standard tone. The value, ΔI, in the Weber fraction was defined as that difference between the level of the test-plus-standard and the level of the standard (I) which was required for the listener to discriminate a difference between the standard and the test-plus-standard. In the homophasic case, the Weber fraction remained constant for changes in the phase angle of addition, whereas in the antiphasic condition, the Weber fraction decreased for increasing values of the phase angle of addition. For both the homophasic and antiphasic conditions and at all values of the phase angle of addition, the Weber fraction remained a constant as the value of the standard was varied. These results are in agreement with those obtained in studies involving noise masking, lateralization, and the monaural Weber fraction.     

Normalization of irrelevant dimensions in stimulus comparisons

When subjects compared two multidimensional stimuli with respect to a single (relevant) dimension in a same-different task, variation in the irrelevant dimension systematically affected reaction times. For same trials, reaction times increased monotonically with the amount of disparity between the stimuli on the irrelevant dimension. The dimensions were heights and widths of ellipses or hues and tints of color patches. The results were interpreted in terms of a normalization process that internally transforms the irrelevant dimensions of the two stimuli until they are equal. The amount of normalization, and hence same reaction time, increased with increasing disparity on the irrelevant dimension. These results suggest that in order to decide that two objects are equivalent in some criterial respect, it is often necessary to normalize irrelevant disparities.     

Acoustic cues and psychological processes in the perception of natural stop consonants

These studies examined the perceptual role of various components of naturally produced stop consonants (/b, d, g, p, t, k/) in CV syllables. In the first experiment, the context-sensitive voiced formant transitions were removed with a computer-splicing technique. Identification accuracy was 84% when the consonant was presented with the same vowel as had been used to produce it. Performance fell to 66% when the consonant was juxtaposed with a different vowel. The second experiment not only deleted the voiced formant transition, but also replaced the aspiration with silence. Here, identification accuracy dropped substantially, especially for voiceless stops, which had contained devoiced formant transitions in the replaced interval. The pattern of errors suggested that listeners try to extract the missing locus of the consonant from the vowel transition, and in the absence of a vowel transition, they try to extrapolate it from the second formant of the steady-state vowel.     

An fMRI investigation of analogical mapping in metaphor comprehension: the influence of context and individual cognitive capacities on processing demands

This study used fMRI to investigate the neural correlates of analogical mapping during metaphor comprehension, with a focus on dynamic configuration of neural networks with changing processing demands and individual abilities. Participants with varying vocabulary sizes and working memory capacities read 3-sentence passages ending in nominal critical utterances of the form "X is a Y." Processing demands were manipulated by varying preceding contexts. Three figurative conditions manipulated difficulty by varying the extent to which preceding contexts mentioned relevant semantic features for relating the vehicle and topic of the critical utterance to one another. In the easy condition, supporting information was mentioned. In the neutral condition, no relevant information was mentioned. In the most difficult condition, opposite features were mentioned, resulting in an ironic interpretation of the critical utterance. A fourth, literal condition included context that supported a literal interpretation of the critical utterance. Activation in lateral and medial frontal regions increased with increasing contextual difficulty. Lower vocabulary readers also had greater activation across conditions in the right inferior frontal gyrus. In addition, volumetric analyses showed increased right temporo-parietal junction and superior medial frontal activation for all figurative conditions over the literal condition. The results from this experiment imply that the cortical regions are dynamically recruited in language comprehension as a function of the processing demands of a task. Individual differences in cognitive capacities were also associated with differences in recruitment and modulation of working memory and executive function regions, highlighting the overlapping computations in metaphor comprehension and general thinking and reasoning.     

How the brain processes causal inferences in text

Abstract— Theoretical models of text processing, such as the construction-integration framework, pose fundamental questions about causal inference making that are not easily addressed by behavioral studies. In particular, a common result is that causal relatedness has a different effect on text reading times than on memory for the text: Whereas reading times increase linearly as causal relatedness decreases, memory for the text is best for events that are related by a moderate degree of causal relatedness and is poorer for events with low and high relatedness. Our functional magnetic resonance imaging study of the processing of two-sentence passages that varied in their degree of causal relatedness suggests that the inference process can be analyzed into two components, generation and integration, that are subserved by two large-scale cortical networks (a reasoning system in dorsolateral prefrontal cortex and the right-hemisphere language areas). These two cortical networks, which are distinguishable from the classical left-hemisphere language areas, approximately correspond to the two functional relations observed in the behavioral results.     

Brain imaging of tongue-twister sentence comprehension: twisting the tongue and the brain

This study used fMRI to investigate the neural basis of the tongue-twister effect in a sentence comprehension task. Participants silently read sentences equated for the syntactic structure and the lexical frequency of the constituent words, but differing in the proportion of words that shared similar initial phonemes. The manipulation affected not only the reading times and comprehension performance, but also the amount of activation seen in a number of language-related cortical areas. The effect was not restricted to cortical areas known to be involved in articulatory speech programming or rehearsal processes (the inferior frontal gyrus and anterior insula), but also extended to areas associated with other aspects of language processing (inferior parietal cortex) associated with phonological processing and storage.     

Ambiguity in the brain: what brain imaging reveals about the processing of syntactically ambiguous sentences

Two fMRI studies investigated the time course and amplitude of brain activity in language-related areas during the processing of syntactically ambiguous sentences. In Experiment 1, higher levels of activation were found during the reading of unpreferred syntactic structures as well as more complex structures. In Experiments 2A and 2B higher levels of brain activation were found for ambiguous sentences compared with unambiguous sentences matched for syntactic complexity, even when the ambiguities were resolved in favor of the preferred syntactic construction (despite the absence of this difference in previous reading time results). Although results can be reconciled with either serial or parallel models of sentence parsing, they arguably fit better into the parallel framework. Serial models can admittedly be made consistent but only by including a parallel component. The fMRI data indicate the involvement of a parallel component in syntactic parsing that might be either a selection mechanism or a construction of multiple parses.