Discrimination Reversal Conditioning of an Eyeblink Response is Impaired by NMDA Receptor Blockade

In the present study we examined the effects of the specific NMDA receptor antagonist CPP on discrimination reversal learning in rabbits. We report two primary findings. First, the institution of NMDA receptor blockade had no effect on a learned discrimination. Second, after stimulus reversal, CPP treatment impaired acquisition of the discrimination reversal. This impairment manifested itself early in training as a retardation in acquisition of a CR to the new CS+ and late in training as an inability to suppress responsiveness to the new CS-. Given the comparability of the present results with previously published results for phenytoin-treated rabbits, we suggest that the effects of phenytoin on learning in this paradigm is at least in part mediated by its effects on NMDA receptors. We further suggest that these findings emphasize the need to better define the role of NMDA receptor activation and hippocampally-mediated circuits in a variety of associative learning paradigms.     

The Relationship Between Attitudinal Ambivalence and Desire to Quit Smoking Among College Smokers1

Growing evidence shows that attitudes can exist on a bivariate rather than a bipolar plane. This conceptualization provides a more dynamic approach to studying how attitudinal ambivalence (i. e., evaluating an attitude object as both positive and negative) affects smoking‐related behaviors. Based on a sample of 157 college smokers, we obtained preliminary validational support for a smoking‐specific felt attitudinal ambivalence scale. Felt attitudinal ambivalence correlated positively with potential for ambivalence, negative attitudes, and negative as well as positive outcome expectancies related to smoking. Smokers who felt more ambivalent reported a greater desire to quit and were more likely to be contemplators, as defined by the transtheoretical model of behavioral change. In multivariate analyses, felt ambivalence toward smoking predicted desire to quit after controlling for positive and negative attitudes and negative smoking consequences. These results provide promising support for the smoking‐specific felt‐ambivalence scale, and suggest that attitudinal ambivalence should be investigated further as a motivational mechanism to affect smoking cessation.     

A cautionary note on using internal cross validation to select the number of clusters

A highly popular method for examining the stability of a data clustering is to split the data into two parts, cluster the observations in Part A, assign the objects in Part B to their nearest centroid in Part A, and then independently cluster the Part B objects. One then examines how close the two partitions are (say, by the Rand measure). Another proposal is to split the data into k parts, and see how their centroids cluster. By means of synthetic data analyses, we demonstrate that these approaches fail to identify the appropriate number of clusters, particularly as sample size becomes large and the variables exhibit higher correlations.The authors express their thanks to the Sol C. Snider Entrepreneurial Center, Wharton School, for support of this project.     

The three-factor structure of the Eysenck personality inventory revealed by a two-step confirmatory procedure

Evidence for the existence of the assumed three-subscale structure of the Eysenck Personality Inventory has been persistent but tenuous. It was suggested that a substantial reason for this may be the discrepancy between the numbers of items in the Lie (L) scale (9 items) and those in the other two scales [Neuroticism (N) and Extraversion (E)] which have 24 items in each. A two-step confirmatory procedure to circumvent this problem was proposed, involving a two-factor analysis of the Neuroticism and Extraversion items, followed by a three-factor analysis of equal numbers of N, E and L scale items. An analysis of the responses of 386 undergraduates demonstrating the proposed procedure revealed in the first step, quite unequivocally, the presence of Neuroticism and Extraversion factors, and in the second step, a third factor clearly congruent with the L scale.     

A time sharing cross-sectional study of monolinguals and bilinguals at different levels of second language acquisition

Several methodological factors associated with the concurrent activities (finger-tapping) paradigm were considered in a cross-sectional study investigating cerebral patterns of asymmetry in three groups of English-speaking non-Hispanic dextral males at three levels of second language (Spanish) acquisition and one control group of monolinguals. Results revealed the fluent bilinguals to be bilateral and significantly different from other groups for native language tasks in English. Moreover, a priori contrasts indicate that greater right- than left-hand disruption in concurrent tapping may be typical of monolinguals, but can be influenced by other factors. Monolingual reliability test-retest correlations were .77 and .47.     

Response to Michael Sells

In an era when lies and misrepresentations about historical events easily become firmly rooted, Michael Sells's discussion illustrates the importance of careful historical research as a moral enterprise. In addition to the skills of the historian, however, there is also room in this enterprise for those of the ethicist. In particular, I warn against confusing the truth or falsity of claims about one narrow historical period with larger questions about the moral meaning and significance of those claims. Illustrating this, I argue one cannot assess the legitimacy of competing nationhood claims solely on the basis of the deeds of specific actors. Nor should the actions of a single individual like the Grand Mufti of Jerusalem be converted into a totalizing claim about the rights of the Palestinian people.