Bistability and biasing effects in the perception of ambiguous point-light walkers

The perceptually bistable character of point-light walkers has been examined in three experiments. A point-light figure without explicit depth cues constitutes a perfectly ambiguous stimulus: from all viewpoints, multiple interpretations are possible concerning the depth orientation of the figure. In the first experiment, it is shown that non-lateral views of the walker are indeed interpreted in two orientations, either as facing towards the viewer or as facing away from the viewer, but that the interpretation in which the walker is oriented towards the viewer is reported more frequently. In the second experiment the point-light figure was walking backwards, making the global orientation of the point-light figure opposite to the direction of global motion. The interpretation in which the walker was facing the viewer was again reported more frequently. The robustness of these findings was examined in the final experiment, in which the effects of disambiguating the stimulus by introducing a local depth cue (occlusion) or a more global depth cue (applying perspective projection) were explored.     

Visual skills in airport-security screening

Abstract— An experiment examined visual performance in a simulated luggage-screening task. Observers participated in five sessions of a task requiring them to search for knives hidden in x-ray images of cluttered bags. Sensitivity and response times improved reliably as a result of practice. Eye movement data revealed that sensitivity increases were produced entirely by changes in observers' ability to recognize target objects, and not by changes in the effectiveness of visual scanning. Moreover, recognition skills were in part stimulus-specific, such that performance was degraded by the introduction of unfamiliar target objects. Implications for screener training are discussed.     

Are dietary restraint scales valid measures of acute dietary restriction? Unobtrusive observational data suggest not

The finding that dietary restraint scales predict onset of bulimic pathology has been interpreted as suggesting that dieting causes this eating disturbance, despite the dearth of evidence that these scales are valid measures of dietary restriction. The authors conducted 4 studies that tested whether dietary restraint scales were inversely correlated with unobtrusively measured caloric intake. These studies, which varied in foods consumed, settings, and populations, indicated that common dietary restraint scales were largely uncorrelated with acute caloric intake. Results suggest that these scales are not valid measures of short-term dietary restriction and imply that it may be prudent to reinterpret findings from studies thai use these scales, including those that suggest dietary restraint is a risk factor for bulimic pathology.     

Regulatory and ethical principles in research involving children and individuals with developmental disabilities

Children and individuals with developmental disabilities (DD) compared to typical participants are disadvantaged not only by virtue of being vulnerable to risks inherent in research participation but also by the higher likelihood of exclusion from research altogether. Current regulatory and ethical guidelines although necessary for their protection do not sufficiently ensure fair distributive justice. Yet, in view of disproportionately higher burdens of co-occurring physical and mental disorders in individuals with DD, they are better positioned to benefit from research by equitable participation. Greater elucidation of this ethical dilemma is called for by researchers, institutional review boards, and funding agencies to urgently redress the imbalance. This article discusses many of the regulatory principles to ensure better research participation of children and individuals with DD: human rights, validity, distributive justice, beneficence/nonmaleficence, and autonomy.     

Children's competence for assent and consent: a review of empirical findings

This narrative review summarizes the empirical literature on children's competence for consent and assent in research and treatment settings. Studies varied widely regarding methodology, particularly in the areas of participant sampling, situational context studied (e.g., psychological versus medical settings), procedures used (e.g., lab-based vs. real-world approaches), and measurement of competence. This review also identifies several fundamental dilemmas underlying approaches to children's informed consent. These dilemmas, including autonomy versus best interest approaches, legal versus psychological or ethical approaches, child- versus family-based approaches, and approaches that emphasize consent versus those that emphasize assent, have implications for the measurement of children's competence and interpretation of findings. Recommendations for future research in the area of children's informed consent include the use of diverse samples and control groups, development of multidimensional and standardized measures of competence, utilization of multidimensional and standardized measures of competence, utilization of observational methods and longitudinal designs, examination of noncognitive aspects of children's competence and comparison of children's competence for treatment and research decisions.     

A new estimation of the duration of attentional dwell time

How rapidly can attention move from one object to the next? Previous studies in which the dwell time paradigm was used have estimated attentional switch times of 200–500 msec, results incompatible with the search rate estimates of 25–50 msec shown in numerous visual search studies. It has been argued that dwell times are so long in the dwell time paradigm because the attentional shifts measured are unlike those used in visual search. In the present experiment, a variation of a visual search task was used, in which serial endogenous (volitional) deployments of attention were measured directly by means of a probe reaction time task. The experiment revealed a dwell time of about 250 msec, consistent with the faster estimates from other dwell time studies. This result suggests that endogenous shifts of attention may be relatively slow and that the faster attentional shifts estimated from visual search tasks may be due to the involvement of bottom-up processes.     

Brain development in autism: early overgrowth followed by premature arrest of growth

Due to the relatively late age of clinical diagnosis of autism, the early brain pathology of children with autism has remained largely unstudied. The increased use of retrospective measures such as head circumference, along with a surge of MRI studies of toddlers with autism, have opened a whole new area of research and discovery. Recent studies have now shown that abnormal brain overgrowth occurs during the first 2 years of life in children with autism. By 2-4 years of age, the most deviant overgrowth is in cerebral, cerebellar, and limbic structures that underlie higher-order cognitive, social, emotional, and language functions. Excessive growth is followed by abnormally slow or arrested growth. Deviant brain growth in autism occurs at the very time when the formation of cerebral circuitry is at its most exuberant and vulnerable stage, and it may signal disruption of this process of circuit formation. The resulting aberrant connectivity and dysfunction may lead to the development of autistic behaviors. To discover the causes, neural substrates, early-warning signs and effective treatments of autism, future research should focus on elucidating the neurobiological defects that underlie brain growth abnormalities in autism that appear during these critical first years of life.     

Comorbidity in compulsive hoarding: a case report

A 56-year-old male presented with compulsive hoarding along with attention-deficit/hyperactivity disorder and schizotypal personality disorder. Hoarding has been described as difficult to treat both pharmacologically and behaviorally, and this patient's comorbid conditions also contributed to his overall impairment. The patient's treatment regimen of fluvoxamine, amphetamine salts, and risperidone, along with behavioral therapy, has helped with hoarding behaviors, motivation, procrastination, and increased socialization. Hoarding may be a unique subtype of obsessive-compulsive disorder with poorer prognosis and distinct neuroanatomic dysfunction. Augmentation with stimulants may provide benefits in aspects of hoarding such as procrastination, especially in patients with comorbid attention-deficit hyperactivity disorder.     

Impact of recent findings on study design of future autism clinical trials

There are specific challenges to studying the design of pharmacologic trials in child/adolescent and adult autism, such as subject stratification and parallel versus crossover designs. This article describes how optimal study design is influenced by subject selection and outcome measures chosen. Lessons learned in study design from the Research Units on Pediatric Psychopharmacology Autism Network trial with risperidone, Seaver Center trials with fluoxetine and valproate, Dartmouth trials with amantadine, and National Institutes of Health secretin trials are highlighted. The Internet System for Assessing Autistic Children system for managing multicenter clinical trials in autism and statistical issues in autism research are also described.     

Placebo and criminal law

This article considers issues concerning cases where the use of placebo is lawful or is not lawful under aspects of German criminal law. It will differentiate between cases of individual therapy and cases of supervised experiments within the scope of medical tests. Thereby, it reveals that a medication of placebo with regard to an individual patient seems to be lawful if there is no alternative possibility of a better treatment using a chemically effective medicine and if the limits of presumed consent are complied with. On the other hand, in the context of the supervised experiment, the assignment of a patient to a group treated with placebo is only lawful if the patient has been fully informed about the possibilities of a treatment and if the patient has given consent to it. An earlier version of this paper was presented at an international conference, “Placebo: Its Action and Place in Health Research Today,” held in Warsaw, Poland on 12–13 April, 2003. The author’s interests include International Criminal Law, Comparative Criminal Law and Philosophy of Law.