Research on numerical cognition is not limited to symbolic numbers and mathematics but it also includes discrete and continuous magnitudes. Continuous magnitudes are ubiquitous in nature and serve as important cues in everyday life situations. When one tries to choose the plate with more cookies in the cafeteria, they usually do not count the cookies but rather arrive at a fair estimate by comparing such continuous magnitudes. For example, nine cookies on a plate will occupy a larger area and have to be placed denser to each other than five cookies. Recent research has shown that, as opposed to the classical view, the processing of symbolic numbers and non-symbolic numerosities is not independent from such sensory cues. The present dissertation consists of two studies that investigate what psychological processes underlie the interaction between sensory cues and numerical information. Study 1 aimed to replicate and extend the findings of Gebuis & Reynvoet who systematically manipulated the relationship between continuous and discrete magnitudes in a non-symbolic numerical comparison task. The main goal was to assess the stability and the robustness of the influence of sensory cues on numerical comparisons as the originally reported patterns suggest a complex interaction between these two kinds of information that are difficult to reconcile with the classic views on numerical processing. Indeed, the results confirmed that continuous magnitudes have a complex effect on numerical judgements and that their interaction can be either due to incomplete inhibition or due to integration of continuous magnitudes during numerical tasks. Study 2 turned to symbolic numbers and investigated whether inhibition underlies the interaction of continuous sensory properties and numerical information. To this end a novel paradigm was introduced that allowed to investigate well-established electrophysiological correlates of inhibition with numerical stimuli. The results provide evidence that inhibition underlies the interaction between sensory cues and numerical information. Additionally, they show that the paradigm introduced in Study 2 may suitable to investigate these processes across different developmental stages and numeracy levels.
