Interactions between numbers and space : neurobehavioural evidence from children and adults

Mental number representations were examined in this thesis by asking participants to compare either numerical or spatial distances of visually presented number triplets (e.g. 57 64 92), a so-called "numerical landmark test". Varying numerical and spatial distances independently resulted in neutral, congruent, and incongruent conditions. This paradigm was employed in classical reaction time (RT) experiments examining adults (Study 1) and children (Study 2) as well as in a neurofunctional investigation using high-resolution functional magnetic resonance imaging (Study 3). In Study 1 the comparison of numerical distances was influenced by the spatial alignment of the numbers (responses were facilitated on congruent trials and interference effects were present on incongruent trials), representing a so-called "distance congruity effect" (DCE). This finding was taken as evidence for a spatial representation of numbers in form of a so-called "mental number line". No such interaction of numerical information with the spatial decision was observed. These asymmetric findings might be interpreted in terms of relative speed of information processing for the two dimensions or in terms of a parasitic representation of numbers on spatial representations, meaning that established structures representing space are recruited for new uses like number processing. In Study 2 children at the age of 8-9 years also exhibited a DCE when being confronted with the numerical landmark test. Correlations between the size of the DCE and calculation abilities were found to be differently marked for girls and boys, leading us to assume that girls and boys in this age make use of different thinking styles in order to solve calculation problems. For boys, who may prefer visuo-spatial thinking styles, a spatial representation of numbers could be helpful when being confronted with addition or subtraction problems, whereas for girls preferring verbal thinking styles it might be even detrimental. Finally, in Study 3 a reflection of the DCE at the neural level was detected in a distributed network comprising parietal and frontal areas. Identifying brain areas coding for subtraction, visual motion processing, and saccades in the same participants, revealed that these activations comprised regions that code for saccades and calculation. Thus, numerical-spatial interactions may be driven by a network subserving attentional shifts and saccadic eye movements, which might also be involved in calculation. Numerical cognition and calculation might therefore be conceived as operations on a mental number line akin to physical movements along a physical trajectory. In sum, these findings underline the notion that neural circuitries being involved in updating internal representations of space during eye movements have been “recycled” for accommodating numerical functions and operations (Dehaene & Cohen, 2007).

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2009

Author dc:creator

• Lonnemann, Jan

Contributors dc:contributor

• Willmes-von Hinckeldey, Klaus

• info:eu-repo/classification/ddc/150
• Neuropsychologie
• Kognition
• Psychologie
• Zahlenverarbeitung
• neuropsychology
• cognitive psycholgy
• number processing

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113876%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51598