Robust estimation of the hierarchical model for responses and response times

Van der Linden's (2007, Psychometrika, 72, 287) hierarchical model for responses and response times in tests has numerous applications in psychological assessment. The success of these applications requires the parameters of the model to have been estimated without bias. The data used for model fitting, however, are often contaminated, for example, by rapid guesses or lapses of attention. This distorts the parameter estimates. In the present paper, a novel estimation approach is proposed that is robust against contamination. The approach consists of two steps. In the first step, the response time model is fitted on the basis of a robust estimate of the covariance matrix. In the second step, the item response model is extended to a mixture model, which allows for a proportion of irregular responses in the data. The parameters of the mixture model are then estimated with a modified marginal maximum likelihood estimator. The modified marginal maximum likelihood estimator downweights responses of test-takers with unusual response time patterns. As a result, the estimator is resistant to several forms of data contamination. The robustness of the approach is investigated in a simulation study. An application of the estimator is demonstrated with real data.     

Difficult temperament predicts self‐esteem in adolescence

A six‐year longitudinal study investigated the impact of maternal hostile child‐rearing attitudes, role dissatisfaction, and maternal perceptions of adolescent temperamental difficultness on self‐esteem in late adolescence, after controlling for the initial self‐esteem measured in early adolescence. Adolescents (n = 313), derived from the Cardiovascular Risk in Young Finns study, rated their self‐esteem at the study entry at age 12, and six years later at age 18. Maternal reports of child‐rearing attitudes, of role satisfaction, and of the temperament of the adolescent were obtained at the study entry and three years later. Mother's perceptions of adolescent's temperament as difficult at ages 12 and 15 predicted adolescent's self‐reported self‐esteem in late adolescence, whereas earlier self‐esteem did not predict later perceptions of temperament or parenting. We found no evidence that maternal perceptions of parenting indirectly, or after controlling for the initial level, predicted adolescent's self‐reported self‐esteem. Copyright © 2002 John Wiley & Sons, Ltd.     

Enhancing the learning of sport skills through external-focus feedback

The authors examined how the effectiveness of feedback for the learning of complex motor skills is affected by the focus of attention it induces. The feedback referred specifically either to body movements (internal focus) or to movement effects (external focus). In Experiment 1, groups of novices and advanced volleyball players (N = 48) practiced "tennis" serves under internal-focus or external-focus feedback conditions in a 2 (expertise) x 2 (feedback type) design. Type of feedback did not differentially affect movement quality, but external-focus feedback resulted in greater accuracy of the serves than internal-focus feedback during both practice and retention, independent of the level of expertise. In Experiment 2, the effects of relative feedback frequency as a function of attentional focus were examined. A 2 (feedback frequency: 100% vs. 33%) x 2 (feedback type) design was used. Experienced soccer players (N = 52) were required to shoot lofted passes at a target. External-focus feedback resulted in greater accuracy than internal-focus feedback did. In addition, reduced feedback frequency was beneficial under internal-focus feedback conditions, whereas 100% and 33% feedback were equally effective under external-focus conditions. The results demonstrate the effectiveness of effect-related, as opposed to movement-related, feedback and also suggest that there is a need to revise current views regarding the role of feedback for motor learning.     

Viewpoint dependency in the recognition of dynamic scenes

In 3 experiments, the question of viewpoint dependency in mental representations of dynamic scenes was addressed. Participants viewed film clips of soccer episodes from 1 or 2 viewpoints; they were then required to discriminate between video stills of the original episode and distractors. Recognition performance was measured in terms of accuracy and speed. The degree of viewpoint deviation between the initial presentation and the test stimuli was varied, as was both the point of time presented by the video stills and participants' soccer expertise. Findings suggest that viewers develop a viewpoint-dependent mental representation similar to the spatial characteristics of the original episode presentation, even if the presentation was spatially inhomogeneous.     

Hypnotic susceptibility in patients with conversion disorder

Conversion disorder has been associated with hypnotic susceptibility for over a century and is currently still believed to be a form of autohypnosis. There is, however, little empirical evidence for the relation between hypnotic susceptibility and conversion symptoms. The authors compared 50 patients with conversion disorder with 50 matched control patients with an affective disorder on measures of hypnotic susceptibility, cognitive dissociation, and somatoform dissociation. Conversion patients were significantly more responsive to hypnotic suggestions than control patients. In addition, conversion patients showed a significant correlation between hypnotic susceptibility and the number of conversion complaints. These results provide the first evidence of a relationship between hypnotic susceptibility and the presence and number of conversion symptoms.     

Relations among heavy training stress,mood state,and performance for male junior rowers

This study investigated the influence of rapidly increased training volume on performance and recovery-stress state perceived by 10 male junior rowers. The training during the 6-day period amounted to 21.5 +/- 2.2 hr., which was equivalent to an average increase in training load by approximately 100% compared to their average training volume during the previous 4 wk. The time to row 2,000 m on a rowing ergometer and resting cortisol level were significantly increased after the 6-day training period. Scores on subscales of the Recovery Stress Questionnaire for Athletes significantly increased for somatic component of stress (Fatigue) and decreased factor indicating recovery (Social Relaxation) after the heavy training period. A correlation of .63 was found between increased training volume and scores on the Conflicts/Pressure subscale at the end of the heavy training period. Correlations were also found between changes in training volume with changes on subscales of Sleep Quality (r=-.64) and Burnout/Personal Accomplishment (r=-.66). Changes in resting cortisol levels as a result of heavy training stress were related to the changes in the following stress subscales: Social Stress (r=.76), Fatigue (r=.64), Disturbed Breaks (r=.65), and Fitness/Injury (r=.67). Changes in performance, perceived recovery-stress state and resting plasma cortisol level reflect increased stress due to high training. These results suggest that the Recovery Stress Questionnaire for Athletes could be used to evaluate the effects of rapidly increased training volume for male junior rowers.     

Unconscious forces: a survey of some concepts in Indian philosophy

In this article, I examine some traditional Indian conceptions of unconscious mental activity. There are concepts in the Indian philosophical tradition, notably saskāras and vāsanās, which can be taken to refer to unconscious mental states and dispositions. My discussion, which is essentially philosophical by nature, is loosely based on the English philosopher C.D. Broad's distinctions concerning the unconscious. Saskāras, which are interpreted realistically in Indian tradition, may manifest themselves as what I (and Broad) call relatively unconscious states. Evidence for this interpretation can be found in discussions concerning the nature of dream state and the supernatural powers of yogis in Indian tradition. It is interesting to try to view the retributive system of karma as an absolutely unconscious system, but this is not a plausible interpretation of the Indian view of karma.     

How many faces can be processed during a single eye fixation?

The purpose of our study was to estimate the perceptual span for facial information: how many faces can be processed during a single eye fixation. We used a visual-search task, in which the targets and distractors were facial photographs. The task of the observer was to search for and identify a target face in an array of faces. We measured the time needed for one search--threshold search time--by using a multiple-alternative staircase method. The threshold represents the duration of stimulus presentation at which the probability of correct responses was 79%. The array size was varied from 2 x 2 to 8 x 8 faces. Simultaneously with the performance measurements we measured eye movements with a video eye tracker. We found that threshold search time increased with increasing set size nearly linearly. The number of fixations also increased linearly from unity at the smallest set size to about fifteen at the largest set size. The result of 2 x 2 faces during a single fixation gave an estimate of 4 faces for the perceptual span. If, on average, only half of the elements had to be scanned for finding the target, 15 fixations at the largest set size (8 x 8) gave another estimate of 2.13 faces. The mean fixation duration was around 200 ms. Thus, the results suggest that 2-4 faces can be processed during one fixation of about 200 ms.     

Mental relaxation improves long-term incidental visual memory

Experimental evidence has linked increased arousal to enhanced memory retention. There is also evidence that procedures reducing arousal, i.e., mental relaxation, might improve memory, but conflicting results have been reported. To clarify this issue, we studied the effects of a single session of relaxation training on incidental visual long-term memory. Thirty-two relaxation-naive subjects viewed 280 slides without being told that there would be subsequent memory testing. Afterwards, subjects listened to a 12 min relaxation tape; 16 subjects relaxed by following the instructions (relaxation group), and the other 16 subjects pressed a button whenever a body part was mentioned (control group). While listening to the relaxation tape, high frequency heart rate variability (HRV) was greater and low frequency HRV was lower in the relaxation group, implying effective relaxation and increasing parasympathetic activation. The relaxation group had superior memory retention 4 weeks later (p = .004), indicating enhancement of long-term memory performance. This effect could not be explained by retroactive interference experienced in the control group because short-term memory performance immediately after the tape was slightly better in the control group. Retention of materials acquired after the relaxation session remained unaffected, suggesting relaxation has retrograde effects on memory consolidation. Our data demonstrate a favorable influence of relaxation on at least this aspect of learning. Our data also extend previous knowledge on the beneficial effects of ascending parasympathetic stimulation on memory retention in that enhanced long-term memory consolidation may also occur in the presence of central and descending parasympathetic activation triggered by willful psychomotor activity.