Perceived shifts of flashed stimuli by visible and invisible object motion

Perceived positions of flashed stimuli can be altered by motion signals in the visual field-position capture (Whitney and Cavanagh, 2000 Nature Neuroscience 3 954-959). We examined whether position capture of flashed stimuli depends on the spatial relationship between moving and flashed stimuli, and whether the phenomenal permanence of a moving object behind an occluding surface (tunnel effect; Michotte 1950 Acta Psychologica 7 293-322) can produce position capture. Observers saw two objects (circles) moving vertically in opposite directions, one in each visual hemifield. Two horizontal bars were simultaneously flashed at horizontally collinear positions with the fixation point at various timings. When the movement of the object was fully visible, the flashed bar appeared shifted in the motion direction of the circle. But this position-capture effect occurred only when the bar was presented ahead of or on the moving circle. Even when the motion trajectory was covered by an opaque surface and the bar was flashed after complete occlusion of the circle, the position-capture effect was still observed, though the positional asymmetry was less clear. These results show that movements of both visible and 'hidden' objects can modulate the perception of positions of flashed stimuli and suggest that a high-level representation of 'objects in motion' plays an important role in the position-capture effect.     

Masked repetition and phonological priming within and across modalities

Lexical decision latencies to word targets presented either visually or auditorily were faster when directly preceded by a briefly presented (53-ms) pattern-masked visual prime that was the same word as the target (repetition primes), compared with different word primes. Primes that were pseudohomophones of target words did not significantly influence target processing compared with unrelated primes (Experiments 1-2) but did produce robust priming effects with slightly longer prime exposures (67 ms) in Experiment 3. Like repetition priming, these pseudohomophone priming effects did not interact with target modality. Experiments 4 and 5 replicated this general pattern of effects while introducing a different measure of prime visibility and an orthographic priming condition. Results are interpreted within the framework of a bimodal interactive activation model.     

Dodge-ing the issue: Dodge,Javal, Hering,and the measurement of saccades in eye-movement research

Dodge, in 1916, suggested that the French term 'saccade' should be used for describing the rapid movements of the eyes that occur while reading. Previously he had referred to these as type I movements. Javal had used the term 'saccade' in 1879, when describing experiments conducted in his laboratory by Lamare. Accordingly, Javal has been rightly credited with assigning the term to rapid eye movements. In English these rapid rotations had been called jerks, and they had been observed and measured before Lamare's studies of reading. Rapid sweeps of the eyes occur as one phase of nystagmus; they were observed by Wells in 1792 who used an afterimage technique, and they were illustrated by Crum Brown in 1878. Afterimages were used in nineteenth-century research on eye movements and eye position; they were also employed by Hering in 1879, to ascertain how the eyes moved during reading. In the previous year, Javal had employed afterimages in his investigations of reading, but this was to demonstrate that the eyes moved horizontally rather than vertically. Hering's and Lamare's auditory method established the discontinuous nature of eye movements during reading, and the photographic methods introduced by Dodge and others in the early twentieth century enabled their characteristics to be determined with greater accuracy.     

The perception of minimal structures: performance on open and closed versions of visually presented Euclidean travelling salesperson problems

The planar Euclidean version of the travelling salesperson problem (TSP) requires finding a tour of minimal length through a two-dimensional set of nodes. Despite the computational intractability of the TSP, people can produce rapid, near-optimal solutions to visually presented versions of such problems. To explain this, MacGregor et al (1999, Perception 28 1417-1428) have suggested that people use a global-to-local process, based on a perceptual tendency to organise stimuli into convex figures. We review the evidence for this idea and propose an alternative, local-to-global hypothesis, based on the detection of least distances between the nodes in an array. We present the results of an experiment in which we examined the relationships between three objective measures and performance measures of optimality and response uncertainty in tasks requiring participants to construct a closed tour or an open path. The data are not well accounted for by a process based on the convex hull. In contrast, results are generally consistent with a locally focused process based initially on the detection of nearest-neighbour clusters. Individual differences are interpreted in terms of a hierarchical process of constructing solutions, and the findings are related to a more general analysis of the role of nearest neighbours in the perception of structure and motion.     

Endogenous shifts of covert attention operate within multiple coordinate frames: evidence from a feature-priming task

The locations of visual objects and events in the world are represented in a number of different coordinate frameworks. For example, a visual transient is known to attract (exogenous) attention and facilitate performance within an egocentric framework. However, when attention is allocated voluntarily to a particular visual feature (ie endogenous attention), the location of that feature appears to be variously encoded either within an allocentric framework or in a spatially invariant manner. In three experiments we investigated the importance of location for the allocation of endogenous attention and whether egocentric and/or allocentric spatial frameworks are involved. Primes and targets were presented in four conditions designed to vary systematically their spatial relationships in egocentric and allocentric coordinates. A reliable effect of egocentric priming was found in all three experiments, which suggests that endogenous shifts of attention towards targets defined by a particular feature operate in an egocentric representation of visual space. In addition, allocentric priming was also found for targets primed by their colour or shape. This suggests that attending to targets primed by nonspatial attributes results in facilitation that is localised in more than one coordinate frame of spatial reference.     

Do expertise and the degree of perception-action coupling affect natural anticipatory performance?

Two experiments using a temporal occlusion paradigm (the first with expert and novice participants and the second with participants of intermediate skill) were conducted to examine the capability of tennis players to predict the direction of an opponent's service in situ. In both experiments two different response conditions, reflecting differing degrees of perception-action coupling, were employed. In a coupled condition players were required to make a movement-based response identical to that which they would use to hit a return of service in a game situation, whereas in an uncoupled condition a verbal prediction of service direction was required. Experiment 1 provided clear evidence of superior prediction accuracy under the coupled response condition when ball flight was available, plus some limited evidence to suggest that superior prediction accuracy under uncoupled response conditions might hold true if only advance (pre-contact) information was available. Experiment 2 showed the former finding to be a robust one, but was unable to reveal any support for the latter. Experiment 1 also revealed that expert superiority is more apparent for predictions made under natural (coupled) than uncoupled response-mode conditions. Collectively, these findings suggest that different perceptual processes may be in operation in anticipatory tasks which depend on skill level, the type of information presented, and degree of perception-action coupling inherent in the task requirements.     

The Werther effect and assisted suicide

In the course of a large epidemiological study in the region of Basle, Switzerland, from 1992 to 1996, a considerable rise in suicides assisted by the right-to-die society EXIT was uncovered after wide press coverage of an assisted double suicide of a prominent couple in that region in March 1995. Further investigation revealed that the rise of assisted suicides for a period of 2 years after the critical event was statistically significant compared to the 2 years previous to the double suicide. This was especially true for women older than 65 years. Hence, the almost enthusiastic kind of reporting about this event was apt to induce imitation suicides or a "Werther-effect."     

Affective, behavioral, and cognitive functioning in adolescents with multiple suicide attempts

The purpose of this study was to examine affective, behavioral, and cognitive functioning in adolescents with multiple suicide attempts. Forty-seven adolescents with a history of multiple suicide attempts (MA) were compared to 74 single suicide attempters (SA) on psychiatric diagnosis, depressive symptoms, affect regulation, self-mutilation, alcohol use, and hopelessness. Results revealed that the MA group was more likely to be diagnosed with a mood disorder, and reported more severe depressive symptoms and anger, in comparison to the SA group. Behaviorally, the MA group had higher rates of disruptive behavior disorders and higher levels of affect dysregulation and serious self-mutilation than the SA group. Further, greater levels of hopelessness were reported by the MA than the SA group. After controlling for a mood disorder diagnosis, only differences in anger, affect dysregulation, and serious self-mutilation remained significant. Overall, results suggest that treatment with adolescent suicide attempters might specifically target anger and affect dysregulation to reduce risk for future suicidal behavior.     

Budgerigars (Melopsittacus undulatus) copy virtual demonstrators in a two-action test

Juvenile budgerigars (Melopsittacus undulatus) observed thin film transistor video playback of a virtual conspecific demonstrator using its beak to remove a stopper from a food box, either by pulling the object upward or by pushing it downward. Simultaneously (Experiment 1) or subsequently (Experiment 2), the observers were offered a similar stopper box and rewarded with access to food for each removal response, regardless of its direction. Observers of upward movement made a greater proportion of up responses in total and showed a stronger tendency to increase the proportion of up responses over test trials than observers of downward movement. These findings provide the first demonstration of which the authors are aware that birds are able not only to detect and respond to a moving video image but also to copy its movements.     

Technology for independence: a community-based resource center

Despite the prominence of the disability civil rights model--with its values of inclusion and empowerment--the majority of social and policy research conducted to date has not sufficiently included the perspective of persons with disabilities in the research process and as uniquely qualified researchers themselves. This article describes a new project, "Technology for Independence: A Community-Based Resource Center" (CBRC). Over a five-year period, the CBRC will attempt to enhance community and consumer-directed disability organizations to design, implement, and disseminate research that promotes access to and use of assistive technology (AT). The CBRC will use strategies such as leadership training, participatory action research, technical assistance, web-assisted training, and annual symposia. A primary goal of the CBRC is to increase the capacity of community organizations to conduct research on AT that is scientifically rigorous and relevant to disability services, policy, and law.