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The functions of language: an experimental study.
We test between four separate hypotheses (social gossip, social contracts, mate advertising and factual information exchange) for the function(s) of language using a recall paradigm. Subjects recalled the social content of stories (irrespective of whether this concerned social behavior, defection or romantic events) significantly better than they did ecological information. Recall rates were no better on ecological stories if they involved flamboyant language, suggesting that, if true, Miller's "Scheherazade effect" may not be independent of content. One interpretation of these results might be that language evolved as an all-purpose social tool, and perhaps acquired specialist functions (sexual advertising, contract formation, information exchange) at a later date through conventional evolutionary windows of opportunity.
Do birds of a feather flock together? The relationship between similarity and altruism in social networks.
Cooperation requires that individuals are able to identify, and preferentially associate with, others who have compatible preferences and the shared background knowledge needed to solve interpersonal coordination problems. The present study investigates the nature of such similarity within social networks, asking: What do friends have in common? And what is the relationship between similarity and altruism? The results show that similarity declines with frequency of contact; similarity in general is a significant predictor of altruism and emotional closeness; and, specifically, sharing a sense of humor, hobbies and interests, moral beliefs, and being from the same area are the best predictors. These results shed light on the structure of relationships within networks and provide a possible checklist for predicting attitudes toward strangers, and in-group identification.
The link between mental rotation ability and basic numerical representations.
Mental rotation and number representation have both been studied widely, but although mental rotation has been linked to higher-level mathematical skills, to date it has not been shown whether mental rotation ability is linked to the most basic mental representation and processing of numbers. To investigate the possible connection between mental rotation abilities and numerical representation, 43 participants completed four tasks: 1) a standard pen-and-paper mental rotation task; 2) a multi-digit number magnitude comparison task assessing the compatibility effect, which indicates separate processing of decade and unit digits; 3) a number-line mapping task, which measures precision of number magnitude representation; and 4) a random number generation task, which yields measures both of executive control and of spatial number representations. Results show that mental rotation ability correlated significantly with both size of the compatibility effect and with number mapping accuracy, but not with any measures from the random number generation task. Together, these results suggest that higher mental rotation abilities are linked to more developed number representation, and also provide further evidence for the connection between spatial and numerical abilities.
Can the feel of the haptic interaction modify a user's emotional state
Haptic perception constitutes an important component of our everyday interaction with many products. At the same time, several studies have, in recent years, demonstrated the importance of involving the emotions in the user-product interaction process. The present study was designed to investigate whether haptic interactions can affect, or modulate, people's responses to standardized emotional stimuli. 36 participants completed a self-assessment test concerning their emotional state utilizing as a pointer either a PHANToM device simulating a viscous force field while they moved the stylus, or else a stylus with no force field. During the presentation of the emotional pictures, various physiological parameters were recorded from participants. The results revealed a significant difference in the self-reported arousal associated with the pictures but no significant difference in the physiological measures. The behavioural findings are interpreted in terms of an effect of the haptic feedback on participants' perceived/interpreted emotional arousal. These results suggest that haptic feedback could, in the future, be used to modify participants' interpretation of their physiological states. © 2013 IEEE.
Anti-extinction in the tactile modality.
Patients with extinction fail to report a contralesional stimulus when it is presented at the same time as an ipsilesional stimulus, and patients with unilateral neglect fail to report a contralesional stimulus even when there is no competing ipsilesional stimulus. Whereas extinction and neglect are common following stroke, the related phenomenon of anti-extinction is rare--there are four cases of anti-extinction in the literature, and all four cases demonstrated anti-extinction in the visual modality. Patients with anti-extinction do report a contralesional stimulus when it is presented at the same time as an ipsilesional stimulus; but, like patients with neglect, they fail to report a contralesional stimulus when there is no competing ipsilesional stimulus. We present the first case ofanti-extinction in the tactile modality.
Dissociable effects of surprise and model update in parietal and anterior cingulate cortex.
Brains use predictive models to facilitate the processing of expected stimuli or planned actions. Under a predictive model, surprising (low probability) stimuli or actions necessitate the immediate reallocation of processing resources, but they can also signal the need to update the underlying predictive model to reflect changes in the environment. Surprise and updating are often correlated in experimental paradigms but are, in fact, distinct constructs that can be formally defined as the Shannon information (IS) and Kullback-Leibler divergence (DKL) associated with an observation. In a saccadic planning task, we observed that distinct behaviors and brain regions are associated with surprise/IS and updating/DKL. Although surprise/IS was associated with behavioral reprogramming as indexed by slower reaction times, as well as with activity in the posterior parietal cortex [human lateral intraparietal area (LIP)], the anterior cingulate cortex (ACC) was specifically activated during updating of the predictive model (DKL). A second saccade-sensitive region in the inferior posterior parietal cortex (human 7a), which has connections to both LIP and ACC, was activated by surprise and modulated by updating. Pupillometry revealed a further dissociation between surprise and updating with an early positive effect of surprise and late negative effect of updating on pupil area. These results give a computational account of the roles of the ACC and two parietal saccade regions, LIP and 7a, by which their involvement in diverse tasks can be understood mechanistically. The dissociation of functional roles between regions within the reorienting/reprogramming network may also inform models of neurological phenomena, such as extinction and Balint syndrome, and neglect.
Social brain: Evolution
Increases in brain size within different mammalian lineages, and in particular increases in neocortex volume within primates, appear to be associated with shifts to more intense forms of sociality. In primates, this is reflected in a strong correlation between neocortex volume and social group size, as well as in correlations with various behavioral indices of social complexity. This relationship seems to be underpinned by cognitive abilities such as the theory of mind, which, while specialized for social tasks, may nonetheless be the emergent properties of more fundamental cognitive abilities associated with executive functions. As a result, there is some evidence to suggest that the frontal lobe may play a disproportionate role in managing social skills. © 2009 Elsevier Ltd All rights reserved.
Male infanticide leads to social monogamy in primates.
Although common in birds, social monogamy, or pair-living, is rare among mammals because internal gestation and lactation in mammals makes it advantageous for males to seek additional mating opportunities. A number of hypotheses have been proposed to explain the evolution of social monogamy among mammals: as a male mate-guarding strategy, because of the benefits of biparental care, or as a defense against infanticidal males. However, comparative analyses have been unable to resolve the root causes of monogamy. Primates are unusual among mammals because monogamy has evolved independently in all of the major clades. Here we combine trait data across 230 primate species with a Bayesian likelihood framework to test for correlated evolution between monogamy and a range of traits to evaluate the competing hypotheses. We find evidence of correlated evolution between social monogamy and both female ranging patterns and biparental care, but the most compelling explanation for the appearance of monogamy is male infanticide. It is only the presence of infanticide that reliably increases the probability of a shift to social monogamy, whereas monogamy allows the secondary adoption of paternal care and is associated with a shift to discrete ranges. The origin of social monogamy in primates is best explained by long lactation periods caused by altriciality, making primate infants particularly vulnerable to infanticidal males. We show that biparental care shortens relative lactation length, thereby reducing infanticide risk and increasing reproductive rates. These phylogenetic analyses support a key role for infanticide in the social evolution of primates, and potentially, humans.
Orienting attention within visual short-term memory: development and mechanisms.
How does developing attentional control operate within visual short-term memory (VSTM)? Seven-year-olds, 11-year-olds, and adults (total n = 205) were asked to report whether probe items were part of preceding visual arrays. In Experiment 1, central or peripheral cues oriented attention to the location of to-be-probed items either prior to encoding or during maintenance. Cues improved memory regardless of their position, but younger children benefited less from cues presented during maintenance, and these benefits related to VSTM span over and above basic memory in uncued trials. In Experiment 2, cues of low validity eliminated benefits, suggesting that even the youngest children use cues voluntarily, rather than automatically. These findings elucidate the close coupling between developing visuospatial attentional control and VSTM.
Propositional learning is a useful research heuristic but it is not a theoretical algorithm
Mitchell et al.'s claim, that their propositional theory is a single-process theory, is illusory because they relegate some learning to a secondary memory process. This renders the single-process theory untestable. The propositional account is not a process theory of learning, but rather, a heuristic that has led to interesting research. © 2009 Cambridge University Press.
Visual attention in the first years: typical development and developmental disorders.
The development of attention is critical for the young child's competence in dealing with the demands of everyday life. Here we review evidence from infants and preschool children regarding the development of three neural subsystems of attention: selective attention, sustained attention, and attentional (executive) control. These systems overlap with dorsal cortical visual streams and their disorders are related to the general hypothesis of 'dorsal stream vulnerability'. Infants' ability to control spatial selective attention can be measured using the 'Fixation Shift' task. From around 4 months of age, infants start to show cortical control in disengaging to switch between competing targets. Fixation shifts have proved to be an effective early indicator of attentional disorders associated with perinatal brain damage. Executive function emerges slowly, starting around 1 year of age. The new Early Childhood Attention Battery has identified the three attention subsystems as distinct before 5 years of age in typical development and allows assessment of individual attention profiles across these subsystems. The Early Childhood Attention Battery is now being used to identify specific profiles associated with developmental syndromes such as Williams, Down, and fragile X. These new methods offer the possibility of very early identification of attention disorders, raising the challenge of effective remediation and treatment at an early age.
Cortical vision, MRI and developmental outcome in preterm infants.
OBJECTIVES: To test two measures of visual cortical function in the first year of life as early markers of functionally significant brain damage in infants born preterm: orientation-reversal visual event-related potentials (OR-VERP) and a behavioural test of cortically controlled visual attention-fixation shifts under competition (FS). Also to examine how these measures relate to (1) perinatal brain insults identified by MRI, and (2) later neurodevelopmental status. PATIENTS AND METHODS: After neonatal and term-age-equivalent MRI, 26 preterm infants (<32 weeks of gestational age, mean 28.1 weeks) were given the OR-VERP and FS tests before 12 months post-term age and a neurodevelopmental assessment (Griffiths Scales) at 2 years. MRI scans examined for parenchymal lesions, intraventricular haemorrhage, ventricular dilatation and diffuse excessive high signal intensity were classified into three categories of severity. Cortical visual test results were compared across these categories and examined as predictors of developmental status at 2 years. RESULTS: 26 infants were studied. 13/25 infants showed significant OR-VERP responses. 12/26 showed normal FS performance. On both tests, the proportion of infants meeting these criteria decreased significantly with MRI severity. As predictors of Griffiths developmental quotient < or =80, the FS test had a sensitivity of 100%, a specificity of 61%, and positive and negative predictive values of 50% and 100%, respectively; corresponding values for OR-VERP were 86%, 65%, 50% and 92% . CONCLUSIONS: Visual cortical tests can provide early indicators of the functional impact of perinatal brain damage in the preterm infant.
Developmental trajectories for spatial frames of reference in Williams syndrome.
Williams syndrome (WS) is a genetic disorder associated with severe visuocognitive impairment. Individuals with WS also report difficulties with everyday wayfinding. To study the development of body-, environment-, and object-based spatial frames of reference in WS, we tested 45 children and adults with WS on a search task in which the participant and a spatial array are moved with respect to each other. Although individuals with WS showed a marked delay, like young controls they demonstrated independent, additive use of body- and environment-based frames of reference. Crucially, object-based (intrinsic) representations based on local landmarks within the array were only marginally used even by adults with WS, whereas in typical development these emerge at 5 years. Deficits in landmark use are consistent with wayfinding difficulties in WS, and may also contribute to problems with basic localization, since in typical development landmark-based representations supplement those based on the body and on self-motion. Difficulties with inhibition or mental rotation may be further components in the impaired ability to use the correct reference frame in WS.
The development of reaching and looking preferences in infants to objects of different sizes.
Reaching and looking preferences and movement kinematics were recorded in 5-15-month-old infants, who were divided into 3 age groups. Infants were presented with pairs of cylinders of 3 different diameters: small (1-cm diameter), medium (2.5-cm diameter), and large (6-cm diameter). Whereas infants between 5 and 12 months of age showed a preference for looking first at the large object, a significant preference for reaching to smaller (graspable) objects was observed in 81/2-12-month-old infants. Kinematic measures suggest that the onset of object-oriented action requires a slowing down of the reach and an extended "homing-in" phase. The divergent looking and reaching preferences in infants at different ages may reflect a dissociation during development of visual processing streams subserving object-related action from those related to visual orienting.
How does noise influence the estimation of speed?
Local motion signals have to be combined in space and time, to yield a coherent motion percept as it is involved in a variety of visual tasks. This combination necessarily means to trade-off between loosing spatio-temporal resolution by pooling local signals and maintaining perceptually significant segmentation between them. When signals are pooled to detect the presence of coherent motion in large amounts of random noise, the question raised is how the noise affects the perceived quality, in particular speed, of the coherent motion. Is there an analogy to the well-known reduction in the perceived speed of moving gratings at low contrast? Using a two-interval forced-choice procedure, we have investigated the assessment of speed in random-dot kinematograms containing different proportions of noise. Under the conditions investigated, there is no strong reduction of perceived speed with increasing noise, as long as coherence levels remain well above the thresholds for directional judgements. This basic result, which could suggest considerable but not perfect segregation of signal and noise motion components in the pooling process leading to speed estimation, is discussed in relation to a model that is designed to decode speed from a population of elementary motion detectors (EMDs) of the correlation type. A strategy to estimate speed from a set of EMDs with a variety of spatio-temporal tuning does not only provide a velocity predictor unambiguous with the spatial structure of the stimulus, but also is largely independent of noise.
Responses to opposed directions of motion: continuum or independent mechanisms?
Opponency between opposite directions of motion is a characteristic of many models of movement detection and is commonly invoked in explanations of the motion after-effect. If detection of opposite directions is mediated by a single mechanism, then a single, smooth psychometric function for the discrimination of global direction in random-dot kinematograms should be found as a function of the percent of directional coherence of dots in the display, ranging from 100% coherence leftwards through 0% coherence to 100% coherence rightwards. Moreover, after rightward motion adaptation, a single psychometric function should still be observed if adaptation affects the perceptual system prior to opponent interactions. If, however, leftward and rightward detectors operate independently, then the slopes of the leftward and rightward halves of the function may differ, particularly after unidirectional adaptation. We measured the probability of a "rightward" direction response for nine values of motion coherence for five observers with and without prior rightward motion adaptation. Although a smooth psychometric function was found without motion adaptation, after adaptation, the rightward half of the psychometric function was flattened whereas the leftward half remained unchanged. Such results indicate that movement direction analysers operate in a non-opponent manner.