Computational theories of vision

This exciting and original book describes the work of David Marr and his colleagues at MIT on the computational theory of vision, particularly the early stages of shape analysis. Although much of the theorising is frankly speculative and not certain to survive without major modification, it sets new standards of rigour in its formal approach and is certain to have a stimulating effect upon the field. Sadly, Marr's death from leukaemia at the age of 35 means that he will not himself be able to take part in the further development of his ideas, but the book itself will exert an important influence for some time to come. The first point to make, for those who may already have attempted Marr's lengthy and difficult research papers, is that the book is clearly and entertainingly written: It can be tackled by the non-specialist who wishes to see why Marr's work has caused such interest in the vision community. Despite the very difficult circumstances in which the book must have been written, it is carefully put together and gives a fascinating insight into the way in which the author's ideas developed.     

Electro-optic shutters and filters

The applications of liquid crystals in perceptual research are examined.     

Family Affluence, School and Neighborhood Contexts and Adolescents’ Civic Engagement: A Cross-National Study

Research on youth civic engagement focuses on individual-level predictors. We examined individual- and school-level characteristics, including family affluence, democratic school social climate and perceived neighborhood social capital, in their relation to civic engagement of 15-year-old students. Data were taken from the 2006 World Health Organization Health Behaviour in School-aged Children survey. A sample of 8,077 adolescents in 10th grade from five countries (Belgium, Canada, Italy, Romania, England) were assessed. Multilevel models were analyzed for each country and across the entire sample. Results showed that family affluence, democratic school climate and perceived neighborhood social capital positively related to participation in community organizations. These links were stronger at the aggregate contextual than individual level and varied by country. Canadian youth participated most and Romanian youth least of the five countries. Gender predicted engagement in two countries (girls participate more in Canada, boys in Italy). Findings showed significant contributions of the social environment to adolescents' engagement in their communities.     

State Patty's Day: College Student Drinking and Local Crime Increased on a Student-constructed Holiday

College student alcohol consumption is a major concern, and is known to increase during the celebration of special events. This study examined a student-constructed holiday, State Patty's Day, at a university with a dominant drinking culture using three sources of data - coded data from Facebook groups, daily web surveys from first-year students (N= 227, 51% male, age 18 to 20; 27.3% Hispanic/Latino; of non-Hispanic/Latino, 26.9% of sample European American/White, 19.4% Asian American/Hawaiian/Pacific Islander, 15.9% African American/Black, 10.6% more than one race), and criminal offense data from police records. Results indicated that messages about State Patty's Day on Facebook focused on drinking and social aspects of the holiday, such as the social context of drinking, a sense of belonging to a larger community, and the social norms of drinking. These messages were rarely about consequences and rarely negative. On State Patty's Day, 51% of students consumed alcohol, compared to 29% across other sampled weekend days. Students consumed more drinks (M = 8.2 [SD = 5.3] drinks per State Patty's Day drinker) and were more likely to engage in heavy drinking on State Patty's Day, after controlling for gender, drinking motives, and weekend, demonstrating the event-specific spike in heavy drinking associated with this holiday. The impact of this student-constructed holiday went beyond individual drinking behavior; alcohol-specific and other crime also peaked on State Patty's Day and the day after. Event-specific prevention strategies may be particularly important in addressing these spontaneous, quickly-constructed, and dynamic events.     

Representations gone mental

Many philosophers and psychologists have attempted to elucidate the nature of mental representation by appealing to notions like isomorphism or abstract structural resemblance. The ‘structural representations’ that these theorists champion are said to count as representations by virtue of functioning as internal models of distal systems. In his 2007 book, Representation Reconsidered, William Ramsey endorses the structural conception of mental representation, but uses it to develop a novel argument against representationalism, the widespread view that cognition essentially involves the manipulation of mental representations. Ramsey argues that although theories within the ‘classical’ tradition of cognitive science once posited structural representations, these theories are being superseded by newer theories, within the tradition of connectionism and cognitive neuroscience, which rarely if ever appeal to structural representations. Instead, these theories seem to be explaining cognition by invoking so-called ‘receptor representations’, which, Ramsey claims, aren’t genuine representations at all—despite being called representations, these mechanisms function more as triggers or causal relays than as genuine stand-ins for distal systems. I argue that when the notions of structural and receptor representation are properly explicated, there turns out to be no distinction between them. There only appears to be a distinction between receptor and structural representations because the latter are tacitly conflated with the ‘mental models’ ostensibly involved in offline cognitive processes such as episodic memory and mental imagery. While structural representations might count as genuine representations, they aren’t distinctively mental representations, for they can be found in all sorts of non-intentional systems such as plants. Thus to explain the kinds of offline cognitive capacities that have motivated talk of mental models, we must develop richer conceptions of mental representation than those provided by the notions of structural and receptor representation.     

Resources required for processing ambiguous complex features in vision and audition are modality specific

Processing multiple complex features to create cohesive representations of objects is an essential aspect of both the visual and auditory systems. It is currently unclear whether these processes are entirely modality specific or whether there are amodal processes that contribute to complex object processing in both vision and audition. We investigated this using a dual-stream target detection task in which two concurrent streams of novel visual or auditory stimuli were presented. We manipulated the degree to which each stream taxed processing conjunctions of complex features. In two experiments, we found that concurrent visual tasks that both taxed conjunctive processing strongly interfered with each other but that concurrent auditory and visual tasks that both taxed conjunctive processing did not. These results suggest that resources for processing conjunctions of complex features within vision and audition are modality specific.