Observers can voluntarily shift their psychometric functions without losing sensitivity

Psychometric sensory discrimination functions are usually modeled by cumulative Gaussian functions with just two parameters, their central tendency (μ) and their slope (1/σ). These correspond to Fechner's "constant" and "variable" errors, respectively. Fechner pointed out that even the constant error could vary over space and time and could masquerade as variable error. We wondered whether observers could deliberately introduce a constant error into their performance without loss of precision. In three-dot vernier and bisection tasks with the method of single stimuli, observers were instructed to favour one of the two responses when unsure of their answer. The slope of the resulting psychometric function was not significantly changed, despite a significant change in central tendency. Similar results were obtained when altered feedback was used to induce bias. We inferred that observers can adopt artificial response criteria without any significant increase in criterion fluctuation. These findings have implications for some studies that have measured perceptual "illusions" by shifts in the psychometric functions of sophisticated observers.     

False feedback increases detection of low-prevalence targets in visual search

Many critical search tasks, such as airport and medical screening, involve searching for targets that are rarely present. These low-prevalence targets are associated with extremely high miss rates Wolfe, Horowitz, & Kenner (Nature, 435, 439?C440, 2005). The inflated miss rates are caused by a criterion shift, likely due to observers attempting to equate the numbers of misses and false alarms. This equalizing strategy results in a neutral criterion at 50?% target prevalence, but leads to a higher proportion of misses for low-prevalence targets. In the present study, we manipulated participants?? perceived number of misses through explicit false feedback. As predicted, the participants in the false-feedback condition committed a higher number of false alarms due to a shifted criterion. Importantly, the participants in this condition were also more successful in detecting targets. These results highlight the importance of perceived prevalence in target search tasks.     

Koffka's effect is mediated by figure thickness at the joining region

Three-quarters of a century ago Gestalt psychologist Kurt Koffka described a remarkable effect: when a contiguous gray ring is placed on a background half one shade of gray, half another, the ring appears homogeneous. However, if the ring is divided, the two halves of the ring appear different shades of gray, the half of the ring on the darker background appearing lighter than the half of the ring on the lighter background. The Gestalt principle of continuity is used to explain this effect. But what microscopic principles might be mediating this effect? Recently we found sufficiently thin rings (annuli) appear heterogeneous even when geometrically continuous. Here, using crescent-shaped figures instead of the circular annuli used for the traditional Koffka effect, we show that this effect of thickness of the ring is mediated by the thickness at the boundary of the region where the halves of the figure are joined.     

Classification and Moral Evaluation of Uncertainties in Engineering Modeling

Engineers must deal with risks and uncertainties as a part of their professional work and, in particular, uncertainties are inherent to engineering models. Models play a central role in engineering. Models often represent an abstract and idealized version of the mathematical properties of a target. Using models, engineers can investigate and acquire understanding of how an object or phenomenon will perform under specified conditions. This paper defines the different stages of the modeling process in engineering, classifies the various sources of uncertainty that arise in each stage, and discusses the categories into which these uncertainties fall. The paper then considers the way uncertainty and modeling are approached in science and the criteria for evaluating scientific hypotheses, in order to highlight the very different criteria appropriate for the development of models and the treatment of the inherent uncertainties in engineering. Finally, the paper puts forward nine guidelines for the treatment of uncertainty in engineering modeling.     

Multiculturalism and Equal Human Dignity: An Essay on Bhikhu Parekh

Bhikhu Parekh is an internationally renowned political theorist. His work on identity and multiculturalism is unquestionably thoughtful and nuanced, benefiting from a tremendous depth of knowledge of particular cases. Despite his work’s many virtues, however, the normative justification for Parekh’s recommendations is at times vague or ambiguous. In this essay, I argue that a close reading of his work, in particular his magnum opus Rethinking Multiculturalism and the selfproclaimed “sequel” A New Politics of Identity, reveals that his claims frequently rely upon a Kantian account of moral dialogue and indeed moral personhood that he remains unwilling to claim. Recognizing this latent Kantianism is essential to a thorough assessment of Parekh’s work on identity, and his criticisms of other theorists. It is only because of his ambiguity that his multiculturalism is able to avoid the sort of charges that he levels against other responses to diversity, including those of such authors as Rawls, Habermas, Kymlicka, and Raz.     

Minimising risks and distractions for young drivers and their passengers: An evaluation of a novel driver–passenger training program

The purpose of the present study was to evaluate a pilot program designed to teach communication skills to young drivers and passengers. Sixty-two young males recruited as 31 pairs of friends, all aged between 18 and 21 years and holding a probationary drivers licence, were randomly assigned to a training or no-training condition. A training program was developed based upon elements of existing team training programs. Driver and passenger pairs operated a driving simulator through scenarios designed to measure aspects of safe driving behaviour and hazard response. Communications between driver and passenger were also measured. All participants were administered the Driver Behaviour Questionnaire before and approximately 2 months after simulator testing. Compared to the untrained group the trained participants exhibited a larger following distance, reduced speed significantly when faced with an unexpected hazard on the road, and exhibited more safe communications. Although current passenger restrictions are warranted, the present results reveal an alternative view of adolescent passengers: rather than being a negative influence on drivers, adolescent passengers can potentially be trained to become a positive influence.     

Ulama, the state, & war: community Islamic leaders in the Aceh conflict

In recent years, much has been said of the relationship between the headmasters of Islamic boarding schools (ulama), the state, and war. Hoping to clarify how ulama behave in times of war and why they react as they do, I look to the recent secessionist conflict in Aceh, Indonesia. Based on extensive village fieldwork, I find that in response to the conflict, Aceh’s ulama were divided; some supported the rebels, some supported the state, and some remained neutral. These positions were largely predicted by combatant control, a pragmatic response to conflict dynamics. Sub-regional comparisons, temporal comparisons, and interviews suggest that while many ulama sided with power, they also sided against human rights abuses, a concern for social justice which may be rooted in religious sentiment after all.