Abstract
In four experiments, we explore the role that verbal WM plays in numerical comparison. Experiment 1 demonstrates that verbal WM load differentially impacts the two most common variants of numerical comparison tasks, evidenced by distinct modulation of the size of the numerical distance effect (NDE). Specifically, when comparing one Arabic digit to a standard, the size of the NDE increases as a function of increased verbal WM load; however, when comparing two simultaneously presented Arabic digits, the size of the NDE decreases (and here is eliminated) as a function of an increased verbal WM load. Experiment 2, using the same task structure but different stimuli (physical size judgments), provides support for the notion that this pattern of results is unique to tasks employing numerical stimuli. Experiment 3 demonstrates that the patterns observed in Experiment 1 are not an artifact of the stimulus pairs used. Experiment 4 provides evidence that the differing pattern of results observed between Experiment 1 and Experiment 2 are due to differences in stimuli (numerical vs. non-numerical) rather than to other differences between tasks. These results are discussed in terms of current theories of numerical comparison.
Highlights
In four experiments, we explore the role that verbal Working memory (WM) plays in numerical comparison
Two participants were removed because their accuracy was below 20% on the WM task, meaning that they did not have enough trials to calculate a reliable score in those cells
We have assessed the role of verbal WM in numerical comparison by examining the effects of verbal WM load on the numerical distance effect (NDE) in two classic numerical cognition tasks
Summary
We explore the role that verbal WM plays in numerical comparison. While a great deal of research exists highlighting both the parallels and differences between comparing symbolic quantities and non-symbolic quantities, (e.g., Maloney, Risko, Preston, Ansari, & Fugelsang, 2010; Holloway & Ansari, 2008), the present paper focuses on the comparison of symbolic quantities This ability to select the larger of two quantities appears to represent a fundamental building block of higher level mathematics as it is related to one’s overall math ability (Holloway & Ansari, 2008). In a simultaneous presentation task, participants see two numbers presented at the same time and are asked to indicate the larger (or the smaller) of the numbers These two tasks elicit NDEs that are comparable in magnitude and, as such, have been used interchangeably in the literature. The NDE has taken a prominent place in studies on numerical cognition, both at the behavioral level (e.g., Dehaene, Dupoux, & Mehler, 1990), and at the neural level (e.g., Holloway & Ansari, 2008) as it is held to provide a critical clue as to how numbers are represented in the mind
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