The rapid extraction of numeric meaning

Several kinds of statistical properties can be rapidly extracted from visual displays (e.g., luminance and roughness, Olive, A., & Torralba, A. (2001). Modeling the shape of the scene: a holistic representation of the spatial envelope. International Journal of Computational Vision, 42, 145-175). Here, we investigate whether this phenomenon extends to meaning contained in Arabic numerals. Observers were shown brief displays containing two sets of numerals and asked to determine which contained the largest average value. Comparisons were made more quickly and accurately between displays of digits than between displays of letters and shapes; this effect could not be attributed to task instructions. When numeric meaning could be used in a classification task, performance was better for digits than for letters, but when numeric meaning could not be used as a basis of classification, performance was approximately equal across stimulus types, suggesting that numeric meaning is rapidly extracted only when it is task-relevant. The digit advantage was eliminated with unlimited viewing time, suggesting that this process is used when counting is not possible. Dual-task methodology revealed that this process requires limited-capacity attentional resources.