Is motion extrapolation employed in multiple object tracking? Tracking as a low-level, non-predictive function

In a series of five experiments, we investigated whether visual tracking mechanisms utilize prediction when recovering multiple reappearing objects. When all objects abruptly disappeared and reappeared mid-trajectory, it was found that (a) subjects tracked better when objects reappeared at their loci of disappearance than when they reappeared in their extrapolated trajectories, (b) disappearance episodes ranging from 150 to 900 ms had virtually no differential effect on performance, (c) tracking deteriorated monotonically as a function of displacement magnitude during disappearance, and (d) tracking did not depend on whether objects moved in predictable paths. Even objects that reappeared backward in their trajectories were tracked dramatically better than objects that reappeared in their extrapolated trajectories. When all objects disappeared and reappeared in ways that implicated the presence of an occluder (i.e., with occlusion and disocclusion cues along fixed contours), tracking again was not predictive, and performance deteriorated with increased displacement. When objects reappeared predictably in 75% of trials, they were still tracked better when they reappeared at their points of disappearance. Theoretical implications of a non-predictive multiple object tracking mechanism are discussed.     

Media representations of environmental issues: From scientific to political discourse

IntroductionThe media is considered to be a social agent that intervenes in the elaboration of social representations of environmental issues.ObjectiveThis research analyses media representations of environmental issues and how they have been constructed and transformed from the Rio Summit in 1992 to 2006. The authors adopted a constructionist approach based on the theory of social representations (Moscovici, 1961/1976) to describe the generation of information by the mass media.MethodA sample of 1039 news articles from two Spanish newspapers (La Vanguardia and El País) was analysed. The period of study ranged from the Rio Earth Summit to several years after the Johannesburg Summit (1992–2006), and the study analyses both the content and form of the environmental news.ResultsThis longitudinal study shows not only an increase in environmental news during the period of analysis but also an increased variety of themes addressed and represented. The results evidence significant urban problems in recent years. The environment has shifted from being associated with nature to being predominately associated with the urban environment.ConclusionThe results suggest that there has been a movement from scientific to political discourse and a change towards greater reflection and social recognition of the relevance of environmental issues.     

Correspondence problems cause repositioning costs in visual working memory

Visual working memory performance often declines when objects are tested in new positions from those they were observed. We report an asymmetry in repositioning costs for orientation compared to colour memory (Experiment 1). Follow-up experiments demonstrated a similar asymmetry for line length memory compared to shape memory (Experiment 2). When different shades of the same colour category were used, however, repositioning costs emerged for colour as well (Experiment 3). Finally, a direct comparison experiment demonstrated an asymmetry for orientation compared to categorical colours, but in a task with no explicit memory demands (Experiment 4). These results challenge previous accounts of repositioning costs, suggesting that they emerge not due to the contents of visual working memory, but naturally because of correspondence procedures that must be executed in order to use a memory to judge the present.     

詹姆士真理观中的休谟因素

与常识的和传统的符合论真理观相比,由詹姆士第一次明确阐述的实用主义真理观有着诸多不同的特点,以及体现在这些特点中的不同的哲学内涵。这些特点和内涵都是怎样产生的呢?在认识论发展的历史进程中有无其根源?该文拟通过联系休谟的经验主义,尤其是他的因果理论,来追溯实用主义真理观的认识论根源。