Disentangling stability, variability and adaptability in human performance: focus on the interplay between local variance and serial correlation

We address the complex relationship between the stability, variability, and adaptability of psychological systems by decomposing the global variance of serial performance into two independent parts: the local variance (LV) and the serial correlation structure. For two time series with equal LV, the presence of persistent long-range correlations (or 1/? β noise) increases the global variance. We hypothesized that a coadjustment between these two determinants of variability constitutes a resource for adaptive systems whose appropriate functioning under critical conditions requires the outcome variance to be limited. To test this hypothesis, we looked at the bimanual coordination dynamics at comfortable (stable) and critical (close to phase transition) frequencies. Results showed that a negative correlation appeared gradually as the theoretical stability of coordination modes decreased and reached significance only in the critical condition. We propose that the emergence of a mutual adjustment between LV and serial correlations might be an indicator of effective adaptation to stabilize behavior.     

Ecology,language, and performance on spatial cognitive tasks

The study of the orientation systems that people use in different cultures to describe the location of objects in space has drawn some interest of researchers in the fields of anthropology, psycholinguistics, and cognitive psychology. There has been a rethinking of the “linguistic relativity hypothesis,” and some empirical studies tend to support the notion that language is the major determinant of encoding and cognitive performance on spatial tasks. This paper reports a cross‐cultural study carried out with 545 children aged 4 to 14 years, both schooled and unschooled, in India and Nepal. The field sites were selected taking into consideration how reference to spatial locations is organized in the language as well as in the local cultural practices. In a village near Varanansi in India, people organize spatial locations mainly with reference to cardinal directions, but in the city of Varanasi, relative references are also used, although people in both the locations speak the same language (i.e., Hindi). In a village in Nepal, on the other hand, the “uphill‐downhill” geocentric frame of reference is the most compelling. We test the relationship between ecology, culture, and language, encoding of spatial information, and performance on some Piagetian spatial tasks, taking age and schooling into account. Berry's eco‐cultural model is used to discuss the findings that support linguistic relativism at the group but not at the individual level. Les systèmes d'orientation spatiale utilisés dans différentes sociétés pour décrire la localisation d'objets ont attiré L'attention de chercheurs en anthropologie, en psycholinguistique et en psychologie cognitive. L'hypothèse du relativisme linguistique a été remise à L'ordre du jour et des études empiriques ont montré que la langue était un déterminant majeur de L'encodage spatial et de la performance à des épreuves de cognition spatiale. Cet article porte sur une étude interculturelle comparative effectuée avec 545 enfants de 4 à 14 ans, scolarisés ou non, en Inde et au Népal. Les trois terrains ont été sélectionnés en tenant compte de la façon dont les références spatiales sont organisées aussi bien dans la langue que dans les pratiques culturelles locales. Dans un village près de Bénares, en Inde, les objets sont localisés selon les points cardinaux, alors que dans la ville de Bénares, des références relatives (droite, gauche, devant, derrière) sont également utilisées, alors que la langue parlée est la même (le Hindi). Dans un village au Népal, le système spatial le plus utilisé est un cadre de référence géocentrique formé par L'opposition «en haut vers la montagne/en bas vers la vallée». Nous étudions les relations entre L'écologie, la culture et la langue, L'encodage d'informations spatiales et la performance à des épreuves spatiales dérivées de la théorie de Piaget, en tenant compte de L'âge et de la scolarisation. Le modèle éco‐culturel de Berry est utilisé comme cadre théorique pour mettre en perspective les résultats, qui confirment le relativisme linguistique au niveau du groupe mais pas au niveau individuel. El estudio de los sistemas de orientación espacial utilizados en diversas culturas para describir la localización de los objetos ha atraído la atención de los investigadores en antropología, psicolingüística y psicología cognitiva. A partir de una renovación de la hipótesis del relativismo lingüístico, algunos estudios empíricos parecen apoyar la noción de que el lenguaje es el determinante más importante de la codificación y el desempeño cognitivo en tareas espaciales. El presente artículo informa sobre un estudio transcultural comparativo, efectuado con 545 niños de 4 a 14 años, escolarizados o no, urbanos y rurales, en India y en Nepal. Los sitios en donde se llevó a cabo el trabajo de campo se seleccionaron tomando en cuenta la forma en que se hace referencia a localizaciones espaciales en la lengua y en las prácticas culturales. En un pueblo de las planicies del Ganges, los habitantes organizan el espacio de manera geocéntrica, según los puntos cardinales, mientras que en la ciudad de Benares, también se utilizan referencias relativas (izquierda/derecha), aún cuando la lengua es la misma (el hindú). En un pueblo de Nepal, el cuadro de referencia geocéntrica “arriba/abajo” es predominante. El presente estudio examinó las relaciones entre la ecología, la cultura, la lengua, la codificación de la información espacial y el desempeño en algunas tareas espaciales de Piaget, teniendo en cuenta la edad y la escolarización. Este estudio está basado en el marco teórico eco‐cultural de Berry. Los resultados confirman una forma moderada de relativismo lingüístico a nivel grupal, más no así a nivel individual.     

Transfer and Scaffolding of Perceptual Grouping Occurs Across Organizing Principles in 3- to 7-Month-Old Infants

ABSTRACT— Previous research has demonstrated that organizational principles become functional over different time courses of development: Lightness similarity is available at 3 months of age, but form similarity is not readily in evidence until 6 months of age. We investigated whether organization would transfer across principles and whether perceptual scaffolding can occur from an already functional principle to a not-yet-operational principle. Six- to 7-month-old infants (Experiment 1) and 3- to 4-month-old infants (Experiment 2) who were familiarized with arrays of elements organized by lightness similarity displayed a subsequent visual preference for a novel organization defined by form similarity. Results with the older infants demonstrate transfer in perceptual grouping: The organization defined by one grouping principle can direct a visual preference for a novel organization defined by a different grouping principle. Findings with the younger infants suggest that learning based on an already functional organizational process enables an organizational process that is not yet functional through perceptual scaffolding.     

Relations between uniform connectedness, luminance, and shape similarity as perceptual organizational cues in infancy

Although several studies have examined infants' sensitivity to perceptual organizational cues, few have examined the functional relations among these cues. We examined how uniform connectedness (UC) functions in relation to shape and luminance similarity. UC has been characterized as the entry-level mechanism of perceptual organization and would therefore be predicted to be more salient than the other two cues. We found that UC was more salient than shape similarity organization was, to the point that 6- to 7-month-old infants failed to even organize on the basis of shape in the presence of UC. Luminance similarity, however, was more salient than UC, even though UC was detected by infants in the presence of luminance cues. We conclude that UC is not necessarily the most salient mechanism of perceptual organization in infancy. Moreover, the luminance-UC-shape salience hierarchy exhibited by 6- to 7-month-olds in the present study is consistent with the order of development of sensitivity to these organizational cues.     

Estimating the spatial Nyquist of the human EEG

The discrete sampling of the brain’s electrical field at the scalp surface with individual recording sensors is subject to the same sampling error as the discrete sampling of the time series at any one sensor with analog-to-digital conversion. Unlike temporal sampling, spatial sampling is intrinsically discrete, so that the post hoc application of analog anti-aliasing filters is not possible. However, the skull acts as a low-pass spatial filter of the brain’s electrical field, attenuating the high spatial frequency information. Because of the skull’s spatial filtering, a discrete sampling of the spatial field with a reasonable number of scalp electrodes is possible. In this paper, we provide theoretical and experimental evidence that adequately sampling the human electroencephalograph (EEG) across the full surface of the head requires a minimum of 128 sensors. Further studies with each of the major EEG and event-related potential phenomena are required in order to determine the spatial frequency of these phenomena and in order to determine whether additional increases in sensor density beyond 128 channels will improve the spatial resolution of the scalp EEG.     

On the time course of exogenous cueing effects in bilinguals: higher proficiency in a second language is associated with more rapid endogenous disengagement

Previous investigations have demonstrated a bilingual advantage on various aspects of executive control. It remains unclear how the language proficiency of bilinguals might relate to the mechanisms involved in attentional disengagement. In the present investigation, we tested the hypothesis that high bilingual proficiency would lead to a more rapid endogenous disengagement of attention from task-irrelevant peripheral cues. We predicted that more rapid attentional disengagement would result in an earlier appearance of inhibition of return (IOR). In this study Hindi-English bilinguals who differed in their L2 (English) proficiency participated in a target detection task. Visual targets were preceded by uninformative peripheral cues at various stimulus onset asynchronies (SOAs) allowing for us to visualize the time course of cue-related facilitation and inhibition. High-proficient Hindi-English bilinguals showed an earlier appearance of IOR than did low-proficient bilinguals, suggesting increased efficiency in disengagement of attention from task-irrelevant inputs. Furthermore, consistent with the "global" advantage that characterizes bilinguals in many tasks, the high-proficient group outperformed low-proficient bilinguals in overall reaction time.     

Piagetian Studies of Cognitive Development in India

The paper presents a review of studies on cognitive development of children in India inspired by Piaget’s theory of cognitive development. Piaget’s theory is briefly introduced before examining its cross-cultural applications. Early studies of cognitive development, which focus on age-related changes in cognition, are described. These are followed by the studies of the last decades in which developmental contexts, such as those provided by ecology, culture, schooling, and various forms of training, are implicated. Studies of spatial cognition are discussed in some detail and points of convergence between findings of Indian studies and those reported by Piaget are critically examined. The issue of “performance” vs. “competence” is addressed and research evidence that considers performance difference as a matter of cognitive style is presented. Possible reasons for decline of research interest in Piagetian studies in recent years is examined and suggestion for future studies in this field are offered.     

Crossing the arms confuses the clocks: Sensory feedback and the bimanual advantage

The bimanual advantage refers to the finding that tapping with two fingers on opposite hands exhibits reduced timing variability, as compared with tapping with only one finger. Two leading theories propose that the bimanual advantage results from the addition of either sensory (i.e., enhanced feedback) or cognitive (i.e., multiple timekeeper) processes involved in timing. Given that crossing the arms impairs perception of tactile stimuli and modulates cortical activation following tactile stimulation, we investigated the role of crossing the arms in the bimanual advantage. Participants tapped unimanually or bimanually with their arms crossed or uncrossed on a tabletop or in the air. With arms crossed, we expected increased interval timing variance. Similarly, for air tapping, we expected reduced bimanual advantage, due to reduced sensory feedback. A significant bimanual advantage was observed for the uncrossed, but not the crossed posture in tabletop tapping. Furthermore, removing tactile feedback from taps eliminated the bimanual advantage for both postures. Together, these findings suggest that crossing the arms likely impairs integration of internal (i.e., effector-specific) and external (i.e., environment-specific) information and that this multisensory integration is crucial to reducing timing variability during repetitive coordinated bimanual tasks.     

Dynamic deformation of shape-memory alloys: Evidence of domino detwinning?

Deformation of NiTi shape-memory alloys (SMAs) under dynamic tension has been studied. It is found that the stress plateau associated with detwinning still exists at the highest strain rate tested (300s -1 ). Beyond the stress plateau, when dislocation mechanisms dominate the deformation process, the strain-hardening effect is more strongly dependent on strain rate. The dynamically deformed specimens exhibit a shape-recovery process and a two-way memory effect which are identical with that for the alloy deformed under quasistatic conditions. The observations suggest that the detwinning process takes place in SMAs under dynamic tension.     

Characterization of the aggregated phase in KCl:Cd2+ and KCl:Mn2+ by Raman spectroscopy

Abstract

The aggregated phase of the impurities in the systems KCl:Cd²⁺ and KCl:Mn²⁺ has been identified as the Suzuki phase by Raman spectroscopy. The linear increase in the integrated scattering intensities of the Raman lines with concentration of the impurities may be attributed to an increase in the mean precipitate size of the Suzuki phase.