Shedding new light on an old problem: The estimation of shadow sizes in children and adults

Two experiments using the 'projection of shadows' paradigm investigated multidimensional reasoning, implicit and explicit knowledge, and the nonlinearity concept in 5-, 9-, and 13-year-olds and adults. Participants estimated the resulting shadow lengths of differently sized objects, placed at varying distances from a light source. Experiment 1 (N=80) revealed that, on the group level, 5-year-olds took both object size and light-object distance into account when estimating shadow size. Moreover, half of the children in this age group even considered the subordinate distance dimension. In addition, we found a large discrepancy between implicit and explicit knowledge about shadows in 5-year-olds that decreased with age. Finally, only a minority of older participants and very few younger children recognized the nonlinear relationship between light-object distance and shadow size, suggesting domain dependence of the nonlinearity concept. Experiment 2 (N=20) predominately replicated the findings for 5-year-olds using slightly different stimuli.     

Overshadowing of subsequent events and recovery thereafter

Four experiments using a conditioned lick suppression preparation with rats were conducted to examine whether overshadowing of subsequent events could be obtained in Pavlovian backward conditioning (i.e. unconditioned stimulus [US] before conditioned stimulus [CS]), and to determine whether such overshadowing could be reversed without further training with the overshadowed CS, as has been reported in overshadowing of antecedent events. In Experiment 1, a backward-conditioned CS overshadowed a second backward-conditioned CS. Two posttraining manipulations, extinction of the overshadowing CS (Experiment 2) and shifting of the temporal relationship of the overshadowing CS to the US (Experiment 3), increased responding to the overshadowed CS. These results constitute the first unambiguous demonstration of stimulus competition between subsequent events using first-order conditioning, and they show that, like overshadowing with forward conditioning, such overshadowing is due, at least in part if not completely, to a failure to express information that had been acquired.     

No effect of synesthetic congruency on temporal ventriloquism

A sound presented in temporal proximity to a light can alter the perceived temporal occurrence of that light (temporal ventriloquism). Recent studies have suggested that pitch-size synesthetic congruency (i.e., a natural association between the relative pitch of a sound and the relative size of a visual stimulus) might affect this phenomenon. To reexamine this, participants made temporal order judgements about small- and large-sized visual stimuli while high- or low-pitched tones were presented before the first and after the second light. We replicated a previous study showing that, at large sound-light intervals, sensitivity for visual temporal order was better for synesthetically congruent than for incongruent pairs. However, this congruency effect could not be attributed to temporal ventriloquism, since it disappeared at short sound-light intervals, if compared with a synchronous audiovisual baseline condition that excluded response biases. In addition, synesthetic congruency did not affect temporal ventriloquism even if participants were made explicitly aware of congruency before testing. Our results thus challenge the view that synesthetic congruency affects temporal ventriloquism.     

Simple rules for detecting depression

Depressive disorders are major public health issues worldwide. We tested the capacity of a simple lexicographic and noncompensatory fast and frugal tree (FFT) and a simple compensatory unit-weight model to detect depressed mood relative to a complex compensatory logistic regression and a naïve maximization model. The FFT and the two compensatory models were fitted to the Beck Depression Inventory (BDI) score of a representative sample of 1382 young women and cross validated on the women's BDI score approximately 18 months later. Although the FFT on average inspected only approximately one cue, it outperformed the naïve maximization model and performed comparably to the compensatory models. The heavier false alarms were weighted relative to misses, the better the FFT and the unit-weight model performed. We conclude that simple decision tools—which have received relatively little attention in mental health settings so far—might offer a competitive alternative to complex weighted assessment models in this domain.     

Modality-general benefit of eye-closure on the retrieval of intentionally learned information

The beneficial effect of eye-closure during retrieval was demonstrated in many studies addressing eyewitness memory or memory of episodic events. Fewer studies examined the effect concerning the intentional learning of verbal information. Furthermore, the question of whether the eye-closure effect is modality-specific, boosting visual memory only, or modality-general, boosting also other forms of memory (e.g., auditory memory), is still open. These issues were addressed in the present study. Participants (N = 129) were asked to study aurally and visually presented lists of unrelated nouns (within-subjects). During free recall, participants either kept their eyes open or closed their eyes (between-subjects). Eye-closure resulted in better free recall than keeping the eyes open. Importantly, this effect emerged for both visually and aurally presented word lists, suggesting that the effect of closing the eyes is rather modality-general. The results are discussed with respect to limitations of previous studies and practical implications.     

Social information facilitates learning about novel food sources in adult flower-visiting bats

Animal Cognition - Incorporating novel food sources into their diet is crucial for animals in changing environments. Although the utilization of novel food sources can be learned individually,...     

Defensive aggression in terns: Discrimination and response to individual researchers

The defensive responses of roseate terns (Sterna dougallii) were studied during the middle of the breeding season when all reproductive stages (incubation, chick-hatching, chick-rearing) were represented, to determine the factors affecting levels of nest defense and whether terns responded differently towards a familiar versus an unfamiliar researcher. Defensive aggression generally varied as a function of researcher identity, time of day, section or location in the colony and nest density. These variables explained from 60 to 66% of the variation in defensive aggression. More terns mobbed one researcher with more dive attacks than the other researcher. Terns were more aggressive in areas where the chicks had just hatched and were most vulnerable. © 1993 Wiley-Liss, Inc.     

Thrombolytic treatment of acute cerebral infarction

Stroke is a common cause of death and disability throughout the world. Acute neurologic deficits due to ischemic injury deserve rapid recognition and diagnosis in order to provide effective therapy. Intravenous tissue plasminogen activator (t-PA) provided to carefully selected patients that can be treated within 3 hours of stroke onset results in improved outcome in these patients. Intra-arterial administration of t-PA within a 6-hour window is performed at several academic centers in patients with middle cerebral and other intracranial artery occlusions based on results of one randomized clinical trial and numerous case reports. Although acute therapy of ischemic stroke has received much attention since the approval of intravenous t-PA, only a small percentage of individuals suffering a stroke actually receive t-PA. This article will review the optimal management of the acute stroke patient and discuss thrombolytic clinical trials that have been completed as well as those that are in progress.