Parameter estimation in latent trait models

Latent trait models for binary responses to a set of test items are considered from the point of view of estimating latent trait parameters=( ₁, , _n ) and item parameters=( ₁, , _k ), where _j may be vector valued. With considered a random sample from a prior distribution with parameter, the estimation of (, ) is studied under the theory of the EM algorithm. An example and computational details are presented for the Rasch model.This work was supported by Contract No. N00014-81-K-0265, Modification No. P00002, from Personnel and Training Research Programs, Psychological Sciences Division, Office of Naval Research. The authors wish to thank an anonymous reviewer for several valuable suggestions.     

Event-related brain potentials to grammatical errors and semantic anomalies

Event-related brain potentials (ERPs) were recorded while subjects silently read several prose passages, presented one word at a time. Semantic anomalies and various grammatical errors had been inserted unpredictably at different serial positions within some of the sentences. The semantically inappropriate words elicited a large N400 component in the ERP, whereas the grammatical errors were associated with smaller and less consistent components that had scalp distributions different from that of the N400. This result adds to the evidence that the N400 wave is more closely related to semantic than to grammatical processing. Additional analyses revealed that different ERP configurations were elicited by open-class (“content”) and closed-class (“function”) words in these prose passages.     

Age and cohort effects on personality factor scores across sexes and racial/ethnic groups

Substantial differences exist across ethnic groups and sexes in generational changes in status among groups residing in Hawaii. Despite these generational differences across groups, age differences in personality are remarkably consistent across sexes and racial/ethnic groups, and the few Sex x Age, Ethnicity x Age or Sex x Ethnicity x Age interactions account for little variance in scores. It is concluded that age/generational differences in personality factor scores in these populations result from age and not, to any major degree, from cohort effects.     

Preparing dichotic tapes using a digital music synthesizer

Digital music synthesizers represent audio signals in the form of binary coded numbers. These binary coded numbers can be manipulated by the operator, thereby altering the audio signal in a variety of ways. The present article describes how these capabilities can be used to produce perfectly aligned dichotic tapes in which the stimulus items are matched on all extraneous (timbre, amplitude, duration) factors.     

A low-stress restraint procedure for EEG acquisition in awake rats

A restraint procedure was developed to reduce movement-related artifacts during the acquisition of EEG data from unanesthetized, unparalyzed rats. It combines the low-stress properties of a cloth restraint bag with the improved immobility of a rigid restraint device. The spontaneous behavior of the rat facilitates both the induction of and the subsequent release from restraint.     

The Mediational Role of Perceived Competence in Psychological Adjustment to Rheumatoid Arthritis1

Chronic illnesses such as rheumatoid arthritis (RA) have been linked to poor psychological adjustment, although individual differences in this relationship have been observed. This study examines the role of perceived competence as a mediator between RA and adjustment. Persons with RA (N= 208) were surveyed three times at 6-month intervals concerning several potential antecedents of adjustment (pain, psychosocial impairment, social support, and control beliefs), self-perceived level of competence, and level of adjustment (life satisfaction and depressive symptomatology). Within each observational period strong evidence was obtained for perceived competence as a mediator of adjustment. Longitudinally (across the year) the data were consistent with a mediational model, but strong evidence establishing mediation was not obtained. Implications of these findings, and the importance of examining the role of perceived competence in adaptation to chronic illness, are discussed.     

Tactile attention and the perception of moving tactile stimuli

Three experiments investigated the ability of subjects to identify the direction of movement of a pattern across the skin. In Experiments 1 and 2, subjects were required to identify the direction of movement of a pattern presented to one fingerpad while another moving pattern was being presented to an adjacent fingerpad. Subjects were instructed to attend only to the target location. The results showed that accuracy was consistently higher and reaction times were consistently faster when the two patterns moved in the same direction than when they moved in opposite directions. Both effects were largest when the two patterns were presented simultaneously. In Experiment 3, the nontarget location was the contralateral hand. In this case, performance was not affected by the presentation of the nontarget. Combined, the results suggest that movement information is processed across adjacent fingers even when subjects are explicitly instructed to attend only to one finger. Subjects do appear to be able to restrict attention to a single hand.