Augmenting a colour lexicon

Languages differ markedly in the number of colour terms in their lexicons. The Himba, for example, a remote culture in Namibia, were reported in 2005 to have only a 5-colour term language. We re-examined their colour naming using a novel computer-based method drawing colours from across the gamut rather than only from the saturated shell of colour space that is the norm in cross-cultural colour research. Measuring confidence in communication, the Himba now have seven terms, or more properly categories, that are independent of other colour terms. Thus, we report the first augmentation of major terms, namely green and brown, to a colour lexicon in any language. A critical examination of supervised and unsupervised machine-learning approaches across the two datasets collected at different periods shows that perceptual mechanisms can, at most, only to some extent explain colour category formation and that cultural factors, such as linguistic similarity are the critical driving force for augmenting colour terms and effective colour communication

The local perceptual bias of a non-remote and educated population

In 1977, Navon argued that perception is biased towards the processing of global as opposed to local visual information (or the forest before the trees) and implicitly assumed this to be true across places and cultures. Previous work with normally developing participants has supported this assumption except in one extremely remote African population. Here we explore local-global perceptual bias in normally developing African participants living much less remotely than the African population tested previously. These participants had access to modern artefacts and education but presented with a local bias on a similarity matching Navon task, contrary to Navon’s assumptions. Nevertheless, the urban and more educated amongst these participants showed a weaker local bias than the rural and less educated participants, suggesting an effect of urbanicity and education in driving differences in perceptual bias. Our findings confirm the impact of experience on perceptual bias and suggest that differences in the impact of education and urbanicity on lifestyles around the world can result in profound differences in perceptual style. In addition, they suggest that local bias is more common than previously thought; a global bias might not be universal after all

Reduced Distractibility in a Remote Culture

Background In visual processing, there are marked cultural differences in the tendency to adopt either a global or local processing style. A remote culture (the Himba) has recently been reported to have a greater local bias in visual processing than Westerners. Here we give the first evidence that a greater, and remarkable, attentional selectivity provides the basis for this local bias. Methodology/Principal Findings In Experiment 1, Eriksen-type flanker interference was measured in the Himba and in Western controls. In both groups, responses to the direction of a task-relevant target arrow were affected by the compatibility of task-irrelevant distractor arrows. However, the Himba showed a marked reduction in overall flanker interference compared to Westerners. The smaller interference effect in the Himba occurred despite their overall slower performance than Westerners, and was evident even at a low level of perceptual load of the displays. In Experiment 2, the attentional selectivity of the Himba was further demonstrated by showing that their attention was not even captured by a moving singleton distractor. Conclusions/Significance We argue that the reduced distractibility in the Himba is clearly consistent with their tendency to prioritize the analysis of local details in visual processing

Load and the spatial profile of visual selective attention

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Le profil spatial de l'attention visuelle sélective

Thèse débutée: 01/10/2005 Thèse soumise: 29/09/2009 Thèse soutenue: 08/01/2010Selective attention has been hypothesised to operate at a perceptual level by focusing perceptual resources on the attended location (Lavie, 1995). This thesis examined (1) the shape of the profile of perceptual resources in space and (2) the effect of several factors on the focus of this profile. The spatial profile of perceptual resources was indexed using different measures, namely, a range of measures of distractor interference in the flanker task (Eriksen & Hoffmann, 1972) and performance at detecting a probe in the cue/probe task (Posner, 1980). In all cases, the profile was found to describe a Mexican-hat pattern and this was true whether attention was directed at fixation or to the periphery. The effects of a number of factors on the focus of the Mexican-hat profile, namely, on the efficiency of the perceptual level of selective attention, were investigated. While increasing both perceptual load (i.e., the perceptual difficulty of extracting information) and trait anxiety caused the profile to focus, increasing cognitive load (i.e., the difficulty of a mental task performed in parallel to the selective-attention task) caused it to defocus. These results have two important implications. First, variations in stimulus and task properties (e.g., load) or in individual characteristics (e.g., anxiety) across studies may explain why some studies have reported gradient rather than Mexican-hat patterns; in some studies, perceptual resources may have been defocused, causing the Mexican-hat profile to look like a gradient. Second, contrary to the load theory (Lavie, Hirst, de Fockert, & Viding, 2004), the focus of perceptual resources is controlled not only at perceptual but also at cognitive levels. Cognitive load may therefore change what we see, whether it be an individuated object or the global properties of a scene.Il a été suggéré (ex. Lavie, 1995) que l'attention visuelle opère en focalisant les « ressources perceptives » sur un endroit donné de la scène visuelle. La présente thèse s'intéresse (1) au profil spatial, c'est-à-dire la répartition dans l'espace visuel, des ressources perceptives et (2) aux effets de plusieurs facteurs sur la focalisation des ressources perceptives. Le profil spatial des ressources perceptives est indexé en utilisant plusieurs mesures, notamment un ensemble de mesures d'interférence (produite par des distracteurs) dans la tâche d'Eriksen (Eriksen & Hoffmann, 1972) et une mesure de performance à détecter une cible (apparaissant à un emplacement attendu ou non) dans la tâche de Posner (Posner, 1980). Dans tous les cas, le profil obtenu décrit un ‘chapeau mexicain' et cela est vrai que l'attention visuelle soit dirigée vers le centre ou vers la périphérie du champ visuel. Les effets de plusieurs facteurs sur la focalisation du ‘chapeau mexicain', c'est-à-dire sur l'efficience de l'attention visuelle, sont ensuite explorés. Tandis qu'augmenter la charge perceptive (la difficulté à extraire l'information perceptuelle) et l'anxiété causent une focalisation attentionnelle (c.à.d. un chapeau mexicain plus comprimé), augmenter la charge cognitive (la difficulté d'une tâche mentale effectuée en parallèle de la tâche d'attention visuelle) causent une défocalisation attentionnelle (c.à.d. un chapeau mexicain plus étalé). Ces résultats ont deux implications importantes. Tout d'abord, des différences au niveau des propriétés des stimuli et de la tâche (ex. charges perceptives ou cognitives) ou des caractéristiques individuelles (ex. anxiété) entre différentes études peuvent expliquer pourquoi certaines études ont rapporté un profil attentionnel décrivant un simple « gradient » et d'autres un profil attentionnel décrivant un « chapeau Mexicain » ; dans certaines études, les ressources perceptives étaient plus défocalisées, faisant passer un chapeau mexicain pour un gradient. Deuxièmement, contrairement à ce qui est suggéré dans l'influente théorie sur les charges perceptives et cognitives (Lavie, Hirst, de Fockert, & Viding, 2004), la focalisation des ressources perceptives n'est pas seulement contrôlée à un niveau perceptif, elle est aussi contrôlée à un niveau cognitif. Charger les processus cognitifs affecterait ce que l'on voit, entre un objet isolé (ex. l'arbre) ou les propriétés plus globales de la scène (ex. la forêt)

Independent effects of relevance and arousal on deductive reasoning

International audienceEmotional content can have either a deleterious or a beneficial impact on logicality. Using standard deductive-reasoning tasks, we tested the hypothesis that the interplay of two factors – personal relevance and arousal – determines the nature of the effect of emotional content on logicality. Arousal was assessed using measures of skin conductance. Personal relevance was manipulated by asking participants to reason about semantic contents linked to an emotional event that they had experienced or not. Findings showed that (1) personal relevance exerts a positive effect on logicality while arousal exerts a negative effect, and that (2) these effects are independent of each other

Working memory function is linked to trauma exposure, independently of post-traumatic stress disorder symptoms

International audienceIntroduction: The purpose of the study was to examine how working memory (WM) may be related to exposure to potentially traumatic events and symptoms of post-traumatic stress disorder (PTSD).Method: In four studies, we measured WM function using adaptations of the running span and the reading span tasks. We compared the performance of women reporting experiences of sexual abuse to control participants (total n = 144 controls and 84 victims). We measured severity of the sexual abuse experiences as well as exposure to general life stress.Results: In all studies, trauma-exposed participants showed significantly lower WM function compared to control participants. In addition to traditional null hypothesis testing, we used a mini-meta analysis to estimate the combined estimated effect size of this difference, which was in the moderate range (d = 0.43 with 0.15–0.70 95% confidence interval). Regression equations showed that PTSD symptoms did not mediate the relationship between trauma exposure and WM function.Conclusions: Our results show that trauma exposure per se can be associated with important cognitive correlates even in individuals who do not develop psychopathological reactions

The interacting effect of load and space on visual selective attention

International audienceIn the study of visual attention, two major determinants of our ability to ignore distracting information have been isolated, namely, (1) the spatial separation from the focus of attention and (2) perceptual load. This study manipulated both factors using a dual-task adaptation of the flanker paradigm (Eriksen & Hoffman, 1973). It showed that (1) although attention followed a gradient profile under low perceptual load it followed a Mexican-hat profile under high perceptual load, consistent with the idea that increasing load focuses spatial attention; and (2) increasing perceptual load did not improve overall selectivity: Though selectivity improved at near separations, it was impaired at far ones. Load and spatial separation exert interacting effects