Automaticity in subtractions depends on problem-size

Existe considerable evidencia que muestra que las multiplicaciones y las sumas simples se resuelven de manera directa y automática. Sin embargo, la evidencia sobre la automaticidad de restas y divisiones es menos convincente. Usando el paradigma de interferencia en la operación, el presente estudio explora si el resultado de una resta puede ser recuperado inintencionadamente y el rol que juega el tamaño del problema en este proceso. Sesenta y dos participantes tomaron parte en este estudio y tenían que decidir si el resultado de una adición era o no correcto. En las adiciones incorrectas el resultado podía ser la sustracción de los sumandos (7 + 4 = 3) o un número no relacionado (7 + 4 = 5). Nuestros resultados mostraron más errores y respuestas más lentas en aquellos problemas cuyo resultado era la sustracción de los sumandos que en los problemas no relacionados. Sin embargo, estos resultados sólo se encontraron en problemas pequeños (7 + 4 = 3 vs. 7 + 4 = 5) y no en problemas más grandes (14 + 8 = 6 vs. 14 + 8 = 7). Estos resultados sugieren que las sustracciones pequeñas pueden ser recuperadas directamente, cuestionando la existencia de disociaciones entre operaciones. Argumentamos que dependiendo de nuestra experiencia, las mismas representaciones y procesos pueden estar implicados en la resolución de multiplicaciones, adiciones y sustracciones.The evidence showing that simple multiplications and additions can be solved by direct retrieval is considerable. However evidence about division and subtraction is less compelling. By using a ―cross-operation interference paradigm‖ the present research explores whether subtraction problems can be retrieved without intention and the role of operands‘ problem-size in this process. Sixty-two participants decided whether the displayed addition was correct or not. In ―false additions problems‖ the answer could be the result of the subtractions of the addends (e.g., 7 + 4 = 3) or an unrelated number (e.g., 7 + 4 = 5). Results showed an interference effect, that is, more errors and slower response times in subtraction related problems than in unrelated problems. More importantly, this effect was restricted to small problems (7 + 4 = 3 vs. 7 + 4 = 5), whereas no differences were found for large problems (14 + 8 = 6 vs. 14 + 8 = 7). These results suggest that small subtractions can be retrieved directly as multiplications, questioning a traditional dissociation between operations. We argue that, depending on individual experience, the same representation and processes can be involved in solving additions, subtractions and multiplications.The evidence showing that simple multiplications and additions can be solved by direct retrieval is considerable. However evidence about division and subtraction is less compelling. By using a ―cross-operation interference paradigm‖ the present research explores whether subtraction problems can be retrieved without intention and the role of operands‘ problem-size in this process. Sixty-two participants decided whether the displayed addition was correct or not. In ―false additions problems‖ the answer could be the result of the subtractions of the addends (e.g., 7 + 4 = 3) or an unrelated number (e.g., 7 + 4 = 5). Results showed an interference effect, that is, more errors and slower response times in subtraction related problems than in unrelated problems. More importantly, this effect was restricted to small problems (7 + 4 = 3 vs. 7 + 4 = 5), whereas no differences were found for large problems (14 + 8 = 6 vs. 14 + 8 = 7). These results suggest that small subtractions can be retrieved directly as multiplications, questioning a traditional dissociation between operations. We argue that, depending on individual experience, the same representation and processes can be involved in solving additions, subtractions and multiplications

The impact of long-range-transport on PM1 and PM2.5 at a Central Mediterranean site

Water soluble ions, methanesulfonate, organic and elemental carbon, and metals in PM2.5 and PM1 samples were analysed by Positive Matrix Factorization to identify and quantify major sources of fine particles at a Central Mediterranean site. The cluster analysis of four-day back trajectories was used to determine the dependence of PM2.5 and PM1 levels and composition on air-flows. The cluster analysis has identified six, six, and seven distinct air-flow types arriving at 500, 1500, and 3000 m above sea level (asl), respectively. Slow-west (Wslow) and north-eastern (NE) flows at 500 and 1500 m asl were the most frequent and were associated with the highest PM2.5 and PM1 concentrations. The PM concentrations from combustion sources including biomass burning were at their maximum under north-western (NW) flows. Similarly, the ammonium sulphate source was enhanced under Wslow and NE flows. South-eastern Mediterranean Sea air-flows were associated with the highest PM2.5 concentrations due to the heavy-oil-combustion source and the highest PM2.5 and PM1 concentrations due to the secondary marine source. PM2.5 concentrations due to the reacted dust and traffic source and PM1 concentrations due to the nitrate with reacted dust and mixed anthropogenic source showed no clear dependence on air-flows. This work highlights the different impact of aerosol sources on PM2.5 and PM1 fractions, being PM1 more adequate to control anthropogenic emissions from combustion sources