A nonparametric approach for assessing latent trait unidimensionality

Assuming a nonparametric family of item response theory models, a theory-based procedure for testing the hypothesis of unidimensionality of the latent space is proposed. The asymptotic distribution of the test statistic is derived assuming unidimensionality, thereby establishing an asymptotically valid statistical test of the unidimensionality of the latent trait. Based upon a new notion of dimensionality, the test is shown to have asymptotic power 1. A 6300 trial Monte Carlo study using published item parameter estimates of widely used standardized tests indicates conservative adherence to the nominal level of significance and statistical power averaging 81 out of 100 rejections for examinee sample sizes and psychological test lengths often incurred in practice.The referees' comments were remarkably detailed and greatly enhanced the writeup and sensitized the author to certain pertinent issues. Discussions with Fritz Drasgow, Lloyd Humphreys, Dennis Jennings, Brian Junker, Robert Linn, Ratna Nandakumar, and Robin Shealy were also very useful.This research was supported by the Office of Naval Research under grant N00014-84-K-0186; NR 150-533, and by the National Science Foundation under grant DMS 85-03321.     

Observational learning of two visual discriminations by pigeons: a within-subjects design.

Pigeon's observational learning of successive visual discrimination was studied using within-subject comparisons of data from three experimental conditions. Two pairs of discriminative stimuli were used; each bird was exposed to two of the three experimental conditions, with different pairs of stimuli used in a given bird's two conditions. In one condition, observers were exposed to visual discriminative stimuli only. In a second condition, subjects were exposed to a randomly alternating sequence of two stimuli where the one that would subsequently be used as S+ was paired with the operation of the grain magazine. In a third experimental condition, subjects were exposed to the performance of a conspecific in the operant discrimination procedure. After exposures to conspecific performances, there was facilitation of discriminative learning, relative to that which followed exposures to stimulus and reinforcement sequences or exposures to stimulus sequences alone. Exposure to stimulus and food-delivery sequences enhanced performance relative to exposure to stimulus sequences alone. The differential effects of these three types of exposure were not attributable to order effects or to task difficulty; rather, they clearly were due to the type of exposure.     

Behavioral contrast in fixed-interval components: effects of extinction-component duration.

Seven albino rats were exposed to a multiple schedule of reinforcement in which the two components (fixed interval and extinction) alternated such that a presentation of the extinction component followed each fixed-interval reinforcement. In baseline sessions, the duration of the extinction component was constant and always one-third of the fixed-interval value. Probe sessions contained a probe segment in which the duration of the extinction component was increased; the response rate in fixed-interval components during the probe segment was compared with the response rate in the segments preceding and following the probe. The effect of increasing the duration of the extinction component was studied under three values of fixed interval: 30 s, 120 s, and 18 s, in three successive conditions. Response rate within fixed intervals was a direct function of duration of the extinction component. Pausing at the beginning of the fixed interval decreased as extinction duration increased. These effects were larger and more consistent for the shorter fixed-interval values (18 s and 30 s). These results indicate a functional relation between relative component duration and responding. For the component providing more frequent reinforcement, this could be stated as an inverse relationship between relative component duration and response rate. This relation is similar to findings regarding the ratio of trial and intertrial duration in Pavlovian conditioning procedures, and suggests that behavioral contrast may be related to Pavlovian contingencies underlying the multiple schedule.     

A taxonomy of item response models

A number of models for categorical item response data have been proposed in recent years. The models appear to be quite different. However, they may usefully be organized as members of only three distinct classes, within which the models are distinguished only by assumptions and constraints on their parameters. “Difference models” are appropriate for ordered responses, “divide-by-total” models may be used for either ordered or nominal responses, and “left-side added” models are used for multiple-choice responses with guessing. The details of the taxonomy and the models are described in this paper. The present study was supported in part by two postdoctoral fellowships awarded to Lynne Steinberg: an Educational Testing Service Postdoctoral Fellowship at ETS, Princeton, NJ and an NIMH Individual National Research Service Award at Stanford University, Stanford, CA. Helpful comments by the editor and three anonymous reviewers are gratefully acknowledged.     

Temporal control by signals of interval duration within variable-interval schedules

Rats' lever pressing produced sucrose reinforcers on a variable-interval schedule where, in different conditions, the duration of a stimulus presented immediately after reinforcement was either correlated or uncorrelated with the duration of the current interreinforcement interval. Under the baseline schedule, in which no stimulus was presented, the minimum interreinforcement interval was 8 s and the mean postreinforcement pause of each subject approximated this value. Response rates increased slowly over the first 10 to 15 s and then remained roughly constant throughout the remainder of the interval. In both the correlated and uncorrelated conditions, the added stimulus resulted in the postreinforcement pauses lengthening to values in excess of the duration of the preceding stimulus. This resulted in a poststimulus pause which was, in most cases, roughly constant irrespective of the duration of the preceding stimulus, or of the reinforcement contingencies prevailing immediately after stimulus offset. Local response-rate patterns in the uncorrelated conditions were similar to those obtained under the baseline schedule in which no stimulus was presented. However, in the correlated condition local response rates increased across the remainder of the interreinforcer interval. Further, the rate of acceleration was inversely related to the duration of the preceding stimulus. These results show that a correlation between stimulus duration and the ensuing time to reinforcement can control behavior—a type of temporal control not previously reported.     

INCREASING APPOINTMENT KEEPING BY REDUCING THE CALL-APPOINTMENT INTERVAL

We examined the effect of reducing the interval between a patient's call for an appointment and the appointment itself. In Experiment 1, patients calling a family planning unit of a public health department were assigned appointments within either 1 or 3 weeks of their call. Data on patient “shows” and “no-shows” were recorded weekly for 6 weeks. Show rates for those in the 1-week appointment group were significantly higher than those in the 3-week group. In Experiment 2, patients were assigned to appointment dates either the next operating clinic day (next-day group) or 2 weeks from the call date (2-week group). Show rates for those in the next-day group were significantly better than show rates for patients in the 2-week group. Clinic productivity, time spent with patients, and consumer satisfaction were also assessed. Implications for appointment scheduling are discussed.     

Increase in physiological inhibitory control results in better suppression of unwanted memories

Forgetting or suppressing a memory with unwanted content is just as important as remembering a desirable one. In addition to emphasizing the role of inhibitory control in memory suppression processes, neuropsychological studies have indicated that an intentional inhibition targeting a brain area may exert its inhibitory effects in seemingly unrelated areas through a common inhibitory network. In this study, we aimed to investigate whether the suppression of unwanted memories can be strengthened by recruiting an inhibitory task that can be simultaneously performed with a memory suppression task. Therefore, we manipulated the level of urinary urgency-induced inhibition of participants (N = 180) and test its effect on the suppression of unwanted memories using a Think/No-Think (T/NT) task. The results of our study indicated that individuals with high levels of urinary urgency demonstrated greater memory suppression compared to those with low urinary urgency. Findings and their implications are discussed within the context of cognitive and clinical perspectives, and recommendations are made for future research.     

Effects of acute endurance,strength, and coordination exercise interventions on attention in adolescents: A randomized controlled study

ObjectivesThe aim of this study was to compare three different modes of an acute bout of exercise – endurance, strength, and coordination – in their effects on adolescents' attention.DesignThis was a preregistered, prospective, randomized intervention study with four groups and two distinct measurement occasions.MethodEighty adolescent students aged 15–18 years were randomized to one of three exercise intervention groups (endurance, strength, coordination) or to a non-exercise, control group. The exercise interventions lasted for 25 min. The random assignment to the study groups was stratified according to participants' age and gender. Before and after the exercise intervention, all participants completed the revised d2-test of attention. A 4 × 2 repeated measures ANOVA with contrast-coded test was used as the main analysis method.ResultsAttentional test performance increased from before to after the exercise intervention for all exercise groups, as compared with the control group. The three exercise groups improved equally and did not differ in their attentional scores after the intervention.ConclusionsAn acute bout of exercise was in general beneficial for adolescent students' attention, while the mode of the provided exercise training was not decisive. School directors and teachers are encouraged to incorporate exercise-related breaks into their school plan.     

不确定是坏的么?不确定状态中的错误加工特点及其解释机制

错误是人类决策和行为过程中在所难免的。然而, 错误常常带来不利后果甚至危及生命(如高危作业时的失误)。如何有效监控错误并优化行为对于个体生存和发展至关重要。错误的发生受到内部心理状态影响, 个体常在不确定的情境中做出判断, 不确定状态增强还是削弱错误监控, 是一个重要科学问题, 却存在矛盾结果。在前期积累和理论分析基础上, 本项目拟从人格差异角度探索不确定容忍度的调节作用。不确定容忍度的差异意味着个体对于模糊情境的耐受性和错误的敏感性不同, 因而可能调节不确定状态中的错误加工过程。研究1采用行为实验, 揭示多种不确定情境中(如奖赏/惩罚)错误监控和错误后调整的认知特点, 考察不确定容忍度的调节作用; 研究2通过考察电生理表征、时间加工进程和神经振荡机制等进一步解释这些现象。本项目对于探明不确定状态中的错误加工规律及其人格调节机制具有重要理论价值, 对于促进个体的环境适应、目标达成等具有较好现实意义。