Aunque existen múltiples evidencias respecto de la relación entre la memoria de trabajo (MT) y el rendimiento aritmético, los resultados aún son inconsistentes. El objetivo del presente estudio fue evaluar la contribución única de cada componente de la MT (bucle fonológico, agenda visuo-espacial y ejecutivo central) a la explicación de la varianza de la eficiencia en aritmética básica, durante diferentes momentos del desarrollo escolar. Se evaluaron 285 estudiantes (M edad: 9,58 años, DE = 1,79) de 5 establecimientos educacionales de Santiago y Chillán, Chile, con y sin dificultades en aritmética básica, a través de tareas de MT. Análisis de regresiones jerárquicas mostraron que los componentes de la MT tienen una contribución única a la varianza de la eficiencia en aritmética básica, pero esta varía durante el desarrollo escolar. Análisis de varianza mostraron diferencias en el funcionamiento de la MT entre estudiantes con y sin dificultades en aritmética, lo cual sugiere que el origen de estas dificultades podría estar muy asociado a la MT. Estos resultados tienen especial relevancia para explicar el desarrollo de la cognición numérica durante la edad escolar.Palabras clave: memoria de trabajo, aritmética básica, habilidades numéricas, dificultades de aprendizaje Although several studies have provided evidence for the relation between working memory (WM) and arithmetic performance, results are still inconsistent. The aim of this study was to evaluate the unique contribution of each component of WM (phonological loop, visuo-spatial sketchpad and central executive) to the explained variance of efficiency in simple arithmetic during different moments of school-age development. WM tasks were used to evaluate 285 students (M age = 9.58 years, SD = 1.79), with and without difficulties in simple arithmetic, from 5 schools in Santiago and Chillán, Chile. Hierarchical regression analyses showed that each WM component contributes differently to the variance of efficiency in simple arithmetic; however, this contribution varies throughout students' school-age development. Variance analysis showed differences in WM functioning between students with and without difficulties in arithmetic, which suggests that the origin of such difficulties may be strongly linked to WM. These results are especially relevant for explaining the development of numerical cognition during school age years.Keywords: working memory, simple arithmetic, numeracy skills, learning difficulties La habilidad para realizar operaciones aritméticas es una de las destrezas académicas primarias que los niños aprenden en la escuela y que luego acompaña el desempeño en la sociedad. Las teorías recientes sobre el desarrollo de competencias matemáticas consideran que las capacidades numéricas básicas (e.g., conteo, comparación, estimación) constituyen el andamiaje cognitivo sobre el cual se construyen las destrezas aritméticas de más alto nivel (Feigenson, Dehaene & Spelke, 2004). Sin embargo, varios estudios han revelado que durante la edad escolar existe, ademá...
Basic numerical processing has been regularly assessed using numerical nonsymbolic and symbolic comparison tasks. It has been assumed that these tasks index similar underlying processes. However, the evidence concerning the reliability and convergent validity across different versions of these tasks is inconclusive. We explored the reliability and convergent validity between two numerical comparison tasks (nonsymbolic vs. symbolic) in school-aged children. The relations between performance in both tasks and mental arithmetic were described and a developmental trajectories' analysis was also conducted. The influence of verbal and visuospatial working memory processes and age was controlled for in the analyses. Results show significant reliability (p < .001) between Block 1 and 2 for nonsymbolic task (global adjusted RT (adjRT): r = .78, global efficiency measures (EMs): r = .74) and, for symbolic task (adjRT: r = .86, EMs: r = .86). Also, significant convergent validity between tasks (p < .001) for both adjRT (r = .71) and EMs (r = .70) were found after controlling for working memory and age. Finally, it was found the relationship between nonsymbolic and symbolic efficiencies varies across the sample's age range. Overall, these findings suggest both tasks index the same underlying cognitive architecture and are appropriate to explore the Approximate Number System (ANS) characteristics. The evidence supports the central role of ANS in arithmetic efficiency and suggests there are differences across the age range assessed, concerning the extent to which efficiency in nonsymbolic and symbolic tasks reflects ANS acuity.
To the Editor, The last decades have witnessed an increase in the incidences of skin cancer throughout the world. In Chile, a recent study showed that the mortality rates from malignant melanoma increased by 14% between 1988 and 1998 (1) and the skin cancer incidence rates increased by 101% between 1992 and 2001 in Santiago's hospitals (2). This may be explained by an increased exposure of individuals to UV radiation, mainly due to the hole in the ozone layer and also due to an increase in leisure time and the desire to possess a suntan. In order to reduce the incidence of skin cancer, it is important to educate young people about the danger of excessive sun exposure. The purpose of this study was to analyse the awareness, knowledge and attitudes of Chilean health university students towards sun exposure and sun protection. A total of 265 students (120 males and 145 females), average age 20.1 years, from Santiago, Chile (321S), were recruited for this study. A suitable questionnaire of multichoice questions comprising items examining awareness, knowledge and sun protection measures was constructed. The test was pre tested on a smaller number of students. Some of the questions had more than one answer. The survey was carried out between the months of August and November (winter-spring). The statistical analysis was performed by a w 2 test for heterogeneity. The distribution of Fitzpatrick skin type was: 7.9% skin type I, 41.1% type II, 28.7% type III, 21.1% type IV, 1.1% type V and 0 type VI. In relation to knowledge, a great number of students (99.6%) were aware of the link 'sun-skin cancer'; however, regarding the question on 'suntan and health', only 26.4% declared that a suntan is harmful for health, 87.2% considered it attractive and 22.
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