Global Effect for Numbers, The Influence of Physical Magnitude and Numerical Magnitude on Saccadic Landing Position

Abstract

Previous studies have shown that the global effect is influenced by the low-level features of objects such as size and salience. Saccades land towards the larger, more salient object. In this study the influence of higher level properties such as numerical value was researched. To this end an experiment was designed in which the size congruency effect for numbers was introduced into a task triggering saccadic averaging. The size congruency effect involves the response to numbers as symbols in relation to their physical appearance. Participants were triggered to make fast saccades in a physical condition presenting dots varying in physical size only and a numerical condition presenting numbers differing in symbolic size only. This study shows that the saccadic landing position in the physical condition portrays a distinct deviation towards the larger, more salient stimulus. This deviation was not present in the numerical condition. An effect of numerical magnitude was not recorded. These results are in line with the notion that saccadic averaging is driven by low-level processes.