Cognitive predictors of posttraumatic stress disorder in children: results of a prospective longitudinal study

The present study explored whether cognitive factors specified in the Ehlers and Clark model (Behav. Res. Ther. 38 (2000) 319) of posttraumatic stress disorder (PTSD) predict chronic PTSD in children who had experienced a road traffic accident. Children were assessed at 2 weeks, 3 months, and 6 months after the accident. Data-driven processing during the accident, negative interpretation of intrusive memories, alienation from other people, anger, rumination, thought suppression and persistent dissociation at initial assessment predicted PTSD symptom severity at 3 and 6 months. On the basis of sex and stressor severity variables, 14% of the variance of PTSD symptoms at 6 months could be explained. The accuracy of the prediction increased to 49% or 53% when the cognitive variables measured at initial assessment or 3 months, respectively, were taken into account.     

The role of proprioception in action recognition

This study aimed at evaluating the role of proprioception in the process of matching the final position of one's limbs with an intentional movement. Two experiments were realised with the same paradigm of conscious recognition of one's own limb position from a distorted position. In the first experiment, 22 healthy subjects performed the task in an active and in a passive condition. In the latter condition, proprioception was the only available information since the central signals related to the motor command were likely to be absent. The second experiment was realised with a deafferented patient who suffers from a complete haptic deafferentation, including loss of proprioception. The results first argue in favour of a dominant role of proprioception in action recognition, but they also stress the possible role of central signals. The process of matching the final position of one's limbs with an intended movement and thus of action recognition would be achieved through a comparison process between the predicted sensory consequences of the action, which are stored in its internal model, and the actual sensory consequences of that action.     

From eye movement to cognition: Toward a general framework of inference comment on Liechty et al., 2003

Liechty, Pieters & Wedel (2003) developed a hidden Markov Model (HMM) to identify the states of an attentional process in an advertisement viewing task. This work is significant because it demonstrates the benefits of stochastic modeling and Bayesian estimation in making inferences about cognitive processes based on eye movement data. One limitation of the proposed approach is that attention is conceptualized as an autonomous random process that is affected neither by the overall layout of the stimulus nor by the visual information perceived during the current fixation. An alternative model based on the input-output hidden Markov model (IOHMM; Bengio, 1999) is suggested as an extension of the HMM. The need for further studies that validate the HMM classification results is also discussed.     

Choice in a variable environment: effects of unequal reinforcer distributions

Six pigeons were trained in a procedure in which sessions included seven unsignaled components, each offering two pecking keys, and each providing a potentially different reinforcer ratio between the two keys. Across conditions, various combinations of reinforcer ratios and reinforcer-magnitude ratios were used to create unequal reinforcer distributions between the two alternatives when averaged across a session. The results extended previous research using the same basic procedure that had included only reinforcer distributions symmetrical around 1:1. Data analyses suggested that the variables controlling choice operated at a number of levels: First, individual reinforcers had local effects on choice; second, sequences of successive reinforcers obtained at the same alternative (continuations) had cumulative effects; and, third, when these sequences themselves occurred with greater frequency, their effects further cumulated. A reinforcer obtained at the other alternative following a sequence of continuations (a discontinuation) had a large effect and apparently reset choice to levels approximating the sessional reinforcer ratio.     

Concurrent-schedule performance in transition: changeover delays and signaled reinforcer ratios

Six pigeons were trained in experimental sessions that arranged six or seven components with various concurrent-schedule reinforcer ratios associated with each. The order of the components was determined randomly without replacement. Components lasted until the pigeons had received 10 reinforcers, and were separated by 10-s blackout periods. The component reinforcer ratios arranged in most conditions were 27:1, 9:1, 3:1, 1:1, 1:3, 1:9 and 1:27; in others, there were only six components, three of 27:1 and three of 1:27. In some conditions, each reinforcement ratio was signaled by a different red-yellow flash frequency, with the frequency perfectly correlated with the reinforcer ratio. Additionally, a changeover delay was arranged in some conditions, and no changeover delay in others. When component reinforcer ratios were signaled, sensitivity to reinforcement values increased from around 0.40 before the first reinforcer in a component to around 0.80 before the 10th reinforcer. When reinforcer ratios were not signaled, sensitivities typically increased from zero to around 0.40. Sensitivity to reinforcement was around 0.20 lower in no-changeover-delay conditions than in changeover-delay conditions, but increased in the former after exposure to changeover delays. Local analyses showed that preference was extreme towards the reinforced alternative for the first 25 s after reinforcement in changeover-delay conditions regardless of whether components were signaled or not. In no-changeover-delay conditions, preference following reinforcers was either absent, or, following exposure to changeover delays, small. Reinforcers have both local and long-term effects on preference. The former, but not the latter, is strongly affected by the presence of a changeover delay. Stimulus control may be more closely associated with longer-term, more molar, reinforcer effects.     

Every reinforcer counts: reinforcer magnitude and local preference

Six pigeons were trained on concurrent variable-interval schedules. Sessions consisted of seven components, each lasting 10 reinforcers, with the conditions of reinforcement differing between components. The component sequence was randomly selected without replacement. In Experiment 1, the concurrent-schedule reinforcer ratios in components were all equal to 1.0, but across components reinforcer-magnitude ratios varied from 1:7 through 7:1. Three different overall reinforcer rates were arranged across conditions. In Experiment 2, the reinforcer-rate ratios varied across components from 27:1 to 1:27, and the reinforcer-magnitude ratios for each alternative were changed across conditions from 1:7 to 7:1. The results of Experiment 1 replicated the results for changing reinforcer-rate ratios across components reported by Davison and Baum (2000, 2002): Sensitivity to reinforcer-magnitude ratios increased with increasing numbers of reinforcers in components. Sensitivity to magnitude ratio, however, fell short of sensitivity to reinforcer-rate ratio. The degree of carryover from component to component depended on the reinforcer rate. Larger reinforcers produced larger and longer postreinforcer preference pulses than did smaller reinforcers. Similar results were found in Experiment 2, except that sensitivity to reinforcer magnitude was considerably higher and was greater for magnitudes that differed more from one another. Visit durations following reinforcers measured either as number of responses emitted or time spent responding before a changeover were longer following larger than following smaller reinforcers, and were longer following sequences of same reinforcers than following other sequences. The results add to the growing body of research that informs model building at local levels.     

On the possibility and desirability of constructing a neutral conception of disability

Disagreement about the properattitude toward disability proliferates. Yetlittle attention has been paid to an importantmeta-question, namely, whether ``disability' isan essentially contested concept. If so, recentdebates between bioethicists and the disabilitymovement leadership cannot be resolved. Inthis essay I identify some of the presumptionsthat make their encounters so contentious. Much more must happen, I argue, for anydiscussions about disability policy andpolitics to be productive. Progress depends onconstructing a neutral conception ofdisability, one that neither devaluesdisability nor implies that persons withdisabilities are inadequate. So, first, I clearaway the conceptual underbrush that makes usthink our idea of disability must bevalue-laden. Second, I sketch someconstituents of, and constraints upon, aneutral notion of disability. This revised version was published online in June 2006 with corrections to the Cover Date.     

对变化/分割模型的检验(Ⅱ)

在前一报告的基础上设计了两个实验,对变化／分割模型做进一步的检验,实验３控制目标时距和该时距内的填充数字系列的分割段数以及段的持续时间,操纵段内的项目数;结果显示,数字系列的分割段数明显影响延迟操作条件下的时距估计,而段内的项目数则不影响对时距的估计,实验４控制目标时距和该时距内填充数字系列的分割段数以及段内的项目数,操纵的持续时间,结果显示,对时距的估计取决于被试所傅物时间标尺,四个实验结果表明     

心理福利的结构研究

通过对幸福、福利及经济福利的反思 ,提出了心理福利这一研究课题 ;结合对被试样本的问卷调查 ,经因子分析 ,分别考察了心理福利的三个维度 :自我幸福感、生活满意感和对社会的行为性评价的因子结构 ;以此为基础 ,运用 L ISREL 8构建了心理福利的二阶结构模型。结果显示 ,模型与数据拟合良好。