Motion-induced blindness measured objectively

During central fixation, a moving pattern of nontargets induces repeated temporary blindness to even salient peripheral targets: motion-induced blindness (MIB). Hitherto, behavioral measures of MIB have relied on subjective judgments. Here, we offer an objective alternative that builds on earlier findings regarding the effects of MIB on the detectability of physical target offsets. We propose a small modification of regular MIB displays: Following a variable duration (lead time), one of the targets is physically removed. Subjects are to respond immediately afterward. We hypothesize that illusory target offsets, caused by MIB, are mistaken for physical target offsets and that errors should thus increase with lead time. Indeed, for both nonsalient and salient targets, we found that detection accuracy for physical target offsets dramatically decreased with lead time. We conclude that target offset detection accuracy is a valid objective measure of MIB. With our method, effects of guessing are minimal, and the fitting of psychometric functions is straightforward. In principle, a staircase extension—for more efficient data collection—is also possible.     

Predictors of Multiple Suicide Attempts among Suicidal Black Adolescents

Psychopathology, social support, and interpersonal orientation were studied in relation to suicide attempt status in acutely suicidal, psychiatrically hospitalized Black adolescents and a matched sample of White adolescents. In the total sample, multiple attempters were differentiated by lower perceived support. Within the Black youth subsample, social comparison and positive stimulation from others differentiated multiple attempters from single attempters/ideators. Only suicidal ideation predicted multiple attempts among White youth and only higher interpersonal orientation predicted multiple suicide attempts within Black adolescents.     

Is Law’s Conventionality Consistent with Law’s Objectivity?

Legal positivism’s multi-faceted insistence on the separability of law and morality includes an insistence on the thoroughly conventional status of legal norms as legal norms. Yet the positivist affirmation of the conventionality of law may initially seem at odds with the mind-independence of the existence and contents and implications of legal norms. Mind-independence, a central aspect of legal objectivity, has been seen by some theorists as incompatible with the mind-dependence of conventions. Such a perception of incompatibility has led some anti-positivist theorists to reject the notion of law’s conventionality, and has led some positivist theorists to query law’s mind-independence. What will be contended here is that both camps are mistaken.

Increased cognitive load leads to impaired mobility decisions in seniors at risk for falls

Successful mobility requires appropriate decision-making. Seniors with reduced executive functioning-such as senior fallers-may be prone to poor mobility judgments, especially under dual-task conditions. We classified participants as "At-Risk" and "Not-At-Risk" for falls using a validated physiological falls-risk assessment. Dual-task performance was assessed in a virtual reality environment where participants crossed a simulated street by walking on a manual treadmill while listening to music or conversing on a phone. Those "At-Risk" experienced more collisions with oncoming cars and had longer crossing times in the Phone condition compared to controls. We conclude that poor mobility judgments during a dual-task leads to unsafe mobility for those at-risk for falls.     

Enhancing the Cognitive Vitality of Older Adults

Aging is associated with decline in a multitude of cognitive processes and brain functions. However, a growing body of literature suggests that age-related decline in cognition can sometimes be reduced through experience, cognitive training, and other interventions such as fitness training. Research on cognitive training and expertise has suggested that age-related cognitive sparing is often quite narrow, being observed only on tasks and skills similar to those on which individuals have been trained. Furthermore, training and expertise benefits are often realized only after extensive practice with specific training strategies. Like cognitive training, fitness training has narrow effects on cognitive processes, but in the case of fitness training, the most substantial effects are observed for executive-control processes.     

The chronic psychosocial stress paradigm in male tree shrews: evaluation of a novel animal model for depressive disorders

To improve our knowledge of the causal mechanisms of stress-related disorders such as depression, we need animal models that mirror the situation in patients. One promising model is the chronic psychosocial stress paradigm in male tree shrews, which is based on the territorial behaviour of these animals that can be used to establish naturally occurring challenging situations under experimental control in the laboratory. Co-existence of two males in visual and olfactory contact leads to a stable dominant-subordinate relationship, with subordinates showing distinct stress-induced behavioural and neuroendocrine alterations that are comparable to the symptoms observed during episodes of depression in patients such as constantly elevated circulating glucocorticoid hormones due to a chronic hyperactivity of the hypothalamic-pituitary-adrenal axis. To elucidate whether the chronic psychosocial stress model in tree shrews besides its "face validity" for depression also has "predictive validity", we treated subordinate tree shrews with the tricyclic antidepressant clomipramine and found a time-dependent restoration of both endocrine and behavioural parameters. In contrast, the anxiolytic diazepam was ineffective. Although the chronic psychosocial stress model in tree shrews requires further validation, it has sufficient face, predictive, and construct validity to become an interesting non-rodent model for research on the etiology and pathophysiology of depression.     

The Relationship Between Parental Alcoholism and Adolescent Psychopathology: A Systematic Examination of Parental Comorbid Psychopathology

The relationship between parental alcohol dependence (with and without comorbid psychopathology) and adolescent psychopathology was examined in a sample of 665 13-17 year-old adolescents and their parents. Results indicated that adolescents who had parents diagnosed with alcohol dependence only did not significantly differ from adolescents who had parents with no psychopathology in regard to any of the measures of psychological symptomatology (substance use, conduct disorder, and depression) or clinical diagnoses (alcohol dependence, marijuana dependence, conduct disorder, or depression) assessed. In contrast, adolescents who had parents diagnosed with alcohol dependence and either comorbid drug dependence or depression were more likely to exhibit higher levels of psychological symptomatology. In addition, adolescents who had parents diagnosed with alcohol dependence, depression, and drug dependence were most likely to exhibit psychological problems. These findings underscore the importance of considering parental comorbid psychopathology when examining the relationship between parental alcoholism and offspring adjustment.     

Age-related effects in the marking of old objects in visual search

Two studies were performed to examine potential age-related differences in visual marking. Visual marking is a limited capacity process that enhances visual search through the inhibition of old objects. In Experiment 1, young and old adults performed three different search conditions: a full-element baseline, a half-element baseline, and a gap condition in which they searched through displays similar to the full-element baseline condition but with half of the letters presented before and the other half of the letters and the target presented after a 1000-ms gap. Both old and young adults displayed search slopes in the gap condition that were equivalent to slopes obtained in the half-element condition, suggesting that they were able to successfully inhibit the old letters. In Experiment 2, old and young adults also performed in three different visual search conditions but in this case with targets defined either by a form difference or by a conjunction of form and color. Both old and young adults showed a reduced slope in the gap as compared to the conjunction condition, suggesting inhibition of the old objects. The data are discussed in terms of age-related differences in the top-down control of attention in visual search.     

Using a modified Stroop task to implicitly discern the cognitive organization of alcohol expectancies

Alcohol expectancies have been statistically modeled as memory networks that influence future consumption. To test the organization of expectancies suggested by these models, a modified Stroop color-naming task incorporated expectancy words associated in past research with heavy and light drinking. Light and heavy drinkers ink-named expectancy targets after being cued with an alcohol beverage word or a nonalcohol beverage word. Consistent with predictions derived from statistical models, heavy drinkers displayed significant interference when arousing expectancy words had been primed by an alcohol beverage word, whereas light drinkers displayed significant interference when sedating expectancy targets had been so primed. These results reinforce the idea that mediation o falcohol use by expectancies may be implicit as well as explicit.