Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Exposure-based models of human parsing: Evidence for the use of coarse-grained (nonlexical) statistical records

Several current models of human parsing maintain that initial structural decisions are influenced (or tuned) by the listener's or reader's prior contact with language. The precise workings of these models depend upon the grain, or level of detail, at which previous exposures to language are analyzed and used to influence parsing decisions. Some models are premised upon the use of fine-grained records (such as lexical cooccurrence statistics). Others use coarser measures. The present paper considers the viability of models based exclusively on the use of fine-grained lexical records. The results of several studies are reviewed and the evidence suggests that, if they are to account for the data, experience-based parsers must draw upon records or representations that capture statistical regularities beyond the lexical level. This poses problems for several parsing models in the literature.Aspects of this work were supported by ESRC grant No. R0023 4062 to Don Mitchell, by a Spanish Government grant DGICVT No. PB-92-0656-C04-02 to Fernando Cuetos, and by the Belgian National Fonds voor Wetenschappelijk Onderzoek, of which Marc Brysbaert is a Research Associate. We are grateful to Chuck Clifton, Barbara Hemforth, Martin Pickering, Matt Traxler, and an anonymous reviewer-all of whom made helpful comments on an earlier draft of the paper.     

Aggressivity,inattention, hyperactivity,and impulsivity in boys at high and low risk for substance abuse

Aggressivity, inattention, hyperactivity, and impulsivity are cardinal dimensions of externalizing behavior problems of childhood. They are diagnostic and clinical features of childhood disorders, and are thought to be linked to the subsequent development of adult disorders such as substance abuse (SA). Little is known, however, about the convergent and discriminant validity of these four constructs. We used multiple measures to develop indices of aggressivity, inattention, hyperactivity, and impulsivity in a sample of 10- to 12-year-old boys (N=183) with and without a family history of SA. Data were taken from mother reports, child reports, teacher reports, and laboratory tasks. The study aims were (1) to test the convergent and discriminant validity of aggressivity, inattention, hyperactivity, and impulsivity; (2) to examine whether the data were consistent with a model specifying the four constructs as indicators of one superordinate factor; and (3) to differentiate boys with and without a family history of SA in construct scores. The results supported the convergent and discriminant validity of the four constructs. Although discriminable, the constructs covaried strongly and were consistent with a model specifying them as indicators of a single superordinate factor. Boys with a family history of substance abuse scored higher than control boys on aggressivity, inattention, and impulsivity scores, but the groups did not differ on hyperactivity scores. The results are discussed in terms of the role of childhood behavior problems in vulnerability to SA.This work was supported by the National Institute on Drug Abuse grant No. DA 05605.     

SPEECH PERCEPTION AS A TALKER-CONTINGENT PROCESS

Abstract— To determine how familiarity with a talker's voice affects perception of spoken words, we trained two groups of subjects to recognize a set of voices over a 9-day period One group then identified novel words produced by the same set of talkers at four signal-to-noise ratios Control subjects identified the same words produced by a different set of talkers The results showed that the ability to identify a talker's voice improved intelligibility of novel words produced by that talker The results suggest that speech perception may involve talker-contingent processes whereby perceptual learning of aspects of the vocal source facilitates the subsequent phonetic analysis of the acoustic signal     

Using sociometric measures to predict help seeking behaviors of youth in a positive peer culture program

Sociometric measures were used to predict help seeking behaviors of youth in a residential treatment center. Seventeen female adolescents with conduct disorders were asked to choose three peers in their group who were most popular, similar, and competent. These sociometric measures were correlated with the degree to which the participants would seek help from their peers across four problem scenarios representing actual situations encountered in residential settings. A multiple linear regression analysis suggested that sociometric measures of “competence” was the best predictor of intentions to seek help across the problem scenarios. Discussion focused on the implications of using sociometric measures within a residential treatment setting.     

The WISC-III: A reality check

Although the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) is arguably the best instrument currently available for assessing students' intelligence, its use will present practitioners, especially school psychologists, with some unique challenges. Recent research suggests that significant reductions in special education students' WISC-III Verbal, Performance, and Full Scale IQ scores will be found, compared with their previous WISC-R results. This finding will have a profound impact on special education placement decisions. Specifically, students who were previously found eligible for learning disability programs may now no longer evidence the significant discrepancies necessary in order to receive continued services. Conversely, students earlier identified as “slow learners” may now be eligible to receive services for those classified under the category of educably mentally handicapped. In addition, the notion that the WISC-III may underestimate the ability of certain populations of students requires further exploration. This article will address these issues as well as implications for practitioners presently administering the WISC-III.     

Conditioned Inhibition Produced by Extinction of a Conditioned Stimulus

Four experiments used a conditioned taste aversion procedure to examine the potential for CS-alone extinction treatment to produce a conditioned stimulus that possesses inhibitory properties. In Experiment 1, saccharin was paired with LiCl, and then saccharin was presented alone for several trials to produce extensive behavioral extinction. Animals receiving this treatment were retarded in reacquiring conditioned responding to saccharin relative to control subjects receiving conditioning to the flavor for the first time. In Experiment 2, the extinguished saccharin stimulus was shown to decrease conditioned responding to a known excitor when the two stimuli were presented in compound as a summation test. Experiments 3A and 3B replicated the findings of Experiments 1 and 2 while providing evidence that the effects were not due to the differential effects of neophobia during testing. These three experiments revealed that an extinguished conditioned excitor passes retardation and summation tests for conditioned inhibition. Experiment 4 found that extinction of a known excitor was slowed when the excitor was extinguished in compound with a previously extinguished conditioned stimulus. That is, an extinguished CS provided protection from extinction to another CS, a finding also consistent with the view that extinction produces conditioned inhibition.     

REPEATED EXPOSURE TO SUGGESTION AND THE CREATION OF FALSE MEMORIES

Abstract— The purpose of the present study was to extend research on repetition and illusory truth to the domain of eyewitness suggestibility. Specifically, we assessed whether repeated exposure to suggestion, relative to a single exposure, facilitates the creation of false memory for suggested events. After viewing a video of a burglary, subjects were asked questions containing misleading suggestions, some of which were repeated. Their memory for the source of the suggestions was tested. The results show that following repeated (relative to a single) exposure to suggestion, subjects were more likely to (a) claim with high confidence that they remembered the suggested events from the video (Experiment 1) and (b) claim that they consciously recollected witnessing the suggested events (Experiment 2). The effects of repeated exposure were highly reliable and were observed over retention intervals as long as I week.     

Formal assessment of problem-solving and planning processes in preschool children

While much is known about adult problem-solving, the materials, analyses, and theoretical issues from the adult literature rarely make contact with the tasks typically used to investigate children's thinking. This paper examines the behavior of 4-, 5-, and 6-year-old children attempting to solve a novel variant of the Tower of Hanoi task. Problems varied in difficulty (one to seven moves for the minimum path solution) and in goal type: tower (all objects on one peg) or flat (all pegs occupied). For each problem, children gave verbal statements of their complete solution plan. The Plan Analysis examined performance as a function of goal type and age. Better performance was observed for tower ending problems, and among older children. The Error Analysis revealed that specific error propensities were related to both age and goal type. The Strategic Analysis compared the first move profiles of 6-year-olds to those of several plausible move selection models, and a high degree of correspondence was obtained between specific models and individual children. Young children appear to have rudimentary forms of many of the problem-solving processes previously identified in adults, but they may differ in encoding and representational processes.