Chunking processes in the learning of event sequences: Electrophysiological indicators

The present study investigated whether effects of implicit learning (IL) are due to well-learned and explicitly represented parts of the stimulus material ("chunks"). To this purpose, event-related brain potentials (ERPs) were recorded during an oddball-version of a serial reaction time (RT) task: At unpredictable positions within a 16-item letter sequence, single deviant items replaced an item of the repeatedly presented standard sequence. After acquisition, the "process dissociation procedure" (Jacoby, 1991) was adopted to identify explicitly learned sequence parts for each participant. Acquisition of sequence knowledge was reflected in faster RTs for standard items than for deviant items and in enhanced N2b and P3b components for deviant items. While the ERP effects were obtained for explicitly represented sequence parts only, RT effects were independent of subsequent reproduction performance. These results indicated that (1) ERPs are a valid measure of explicit knowledge, (2) implicit and explicit knowledge coexist in serial RT tasks, and (3) chunking processes play a major role in the acquisition of explicit knowledge about event sequences.     

Sentence Comprehension Is Mediated by Content-Addressable Memory Structures

Studies of working memory demonstrate that some forms of information are retrieved by a content-addressable mechanism (McElree & Dosher, 1989; McElree, 1996, 1998), whereas others require a slower search-based mechanism (McElree & Dosher, 1993). Measures of the speed and accuracy of processing sentences with filler-gap dependencies demonstrate that the probability of maintaining a representation of a filler item decreases as additional material is processed, but that the speed with which a preserved representation is accessed is unaffected by the amount of interpolated material. These results suggest that basic binding operations in sentence comprehension are mediated by a content-addressable memory system.     

Subverting Culture: Promoting HIV/AIDS Prevention Among Puerto Rican and Dominican Women

This article discusses the challenges faced by researchers and interventionists when attempting to promote change in social norms and normative beliefs that promote HIV/AIDS risk-related behaviors among Puerto Rican and Dominican women. The article focuses on the role of culture in HIV/AIDS prevention with women by analyzing the sociohistorical context of some cultural beliefs and by illustrating the tension between risk-related and protective cultural beliefs in research conducted by the authors with women in both New York and Puerto Rico. The authors propose that promoting changes in sex-related social norms and normative beliefs might be constructed as a subversive act and present the challenge this analysis poses for community psychology. They conclude that this conceptualization might be construed as subversive because rather than idealizing culture, it promotes changes that respect diversity within the culture and foster participation in the development of new cultural values, beliefs and norms.     

Behavioral versus Behavioral and Pharmacological Treatment in ADHD Children Attending a Summer Treatment Program

As part of the behavioral treatment in the Multimodal Treatment Study of Children with ADHD (MTA), children participated in an intensive summer treatment program (STP). This study examined the differences between 57 children in the combined treatment (Comb) group, who were medicated, and 60 children in the behavioral treatment (Beh) group, who were unmedicated throughout the STP. Comb children were significantly better than Beh on 5 measures: rule following, good sportsmanship, peer negative nominations, and STP teacher posttreatment ratings of inattention/overactivity. Groups did not differ on any of the other 30 measures, and responded similarly to the STP over time. Comparisons to normative data revealed that Comb children were more likely to fall within the normative range on 6 measures. The differences between these results and the main MTA results, in which Comb was always superior to Beh, are discussed in terms of the relative intensity of combined treatments. The implications for future studies of pharmacological and behavioral treatment for ADHD are discussed.     

Raised line drawings are spontaneously explored with a single finger

In this study we examine the strategies used by blindfolded subjects asked to freely explore raised line drawings and identify what is depicted in them. We were particularly interested in how often a single finger is spontaneously used because in several studies subjects are forced to use only one fingertip and the extent to which this restriction may depress haptic perception is unclear. The results suggest that despite a variety of strategies, people 'naturally' use single fingertips sufficiently often to allow confidence in conclusions that are based on studies imposing this restriction.     

Influence of the movement parameter to be controlled on manual RT asymmetries in right-handers

In this experiment we test whether the effects of manual asymmetries on movement preparation depend on the parameter (amplitude or direction) to be programmed. In two experiments, only the amplitude, or the direction, of aiming movements was constrained. Reaction and movement times were measured. Results show that RTs are always shorter for left-hand than for right-hand movements. There is an effect of target extent in the amplitude condition, but not in the direction one. RTs for ipsilateral movements are shorter than RTs for contralateral movements. These results are discussed in the light of the processes involved in setting the amplitude or direction of the movement and with regard to the competency of the two hemispheres regarding these processes.     

Personal theories, intellectual ability, and epistemological beliefs: adult age differences in everyday reasoning biases

Age-related differences in everyday reasoning biases were explored. In each of 2 social domains, examination of theoretical beliefs and biases along 2 dimensions of scientific reasoning, involving the law of large numbers and the evaluation of experimental evidence, revealed that, across age groups, scientific reasoning was used to reject evidence that contradicted prior beliefs; relatively cursory reasoning was used to accept belief-consistent evidence. Biased reasoning was more common among middle-aged and older adults than among young adults. Dispositions to engage in analytic processing were negatively related to biases, but intellectual abilities and bias were not related. The findings support a 2-process view of adult cognitive development and suggest that the tendency to rely on heuristic information processing increases with age.     

Imaging high-resolution structure of GFP-expressing neurons in neocortex in vivo

To detect subtle changes in neuronal morphology in response to changes in experience, one must image neurons at high resolution in vivo over time scales of minutes to days. We accomplished this by infecting postmitotic neurons in rat and mouse barrel cortex with a Sindbis virus carrying the gene for enhanced green fluorescent protein. Visualized with 2-photon excitation laser scanning microscopy, infected neurons showed bright fluorescence that was distributed homogeneously throughout the cell, including axonal and dendritic arbors. Single dendritic spines could routinely be resolved and their morphological dynamics visualized. Viral infection and imaging were achieved throughout postnatal development up to early adulthood (P 8-30), although the viral efficiency of infection decreased with age. This relatively noninvasive method for fluorescent labeling and imaging of neurons allows the study of morphological dynamics of neocortical neurons and their circuits in vivo.     

Prejudice expectations moderate preconscious attention to cues that are threatening to social identity

Two studies examined whether chronic and situational expectations about being stigmatized predict attention toward cues that are threatening to social identity. In Study 1, women's chronic expectations about experiencing sexism were positively associated with their attention toward subliminal cues threatening to their social identity. In Study 2, women were vigilant toward subliminal cues threatening to their social identity when the experimental situation conveyed that their gender was devalued, but not when the experimental situation promoted value and respect for their gender. Women were vigilant toward consciously presented cues threatening to their social identity regardless of the attitudes the experimental context conveyed toward their group. These studies have important theoretical and practical implications for understanding the psychological experience of possessing a devalued social identity.