The influence of the place-value structure of the Arabic number ...

unit digits indicating decomposed processing of two-digit number magnitude, see also
Study 2) as obtained in third grade assessment.
Section 4: The neuro-cognitive underpinnings of place-value integration
1. Study 5: All for one but not one for all: How multiple number representations are
recruited in one numerical task.
Recently, Goebel et al. (2004) were the first to dissociate the neural correlates of
the representations of single- and two-digit numbers within the IPS suggesting
separate representations for these two power levels. Further on, Wood and colleagues
(2006b) investigated the neural underpinnings of the unit-decade compatibility effect
to evaluate whether there is a specific cortex area (possibly within the IPS) subserving
processes of unit-decade integration. The data by Wood and colleagues (2006b, see
also Knops et al., 2006) were informative on this point and indicated that indeed
neural activation in a circumscribed part of the IPS was determined by unit-decade
compatibility. However, these results were obtained in a magnitude comparison task,
assumed to primarily assess the representation of number magnitude. Therefore, it
would have been interesting to evaluate the validity of these results in a more complex
task known to recruit different numerical representation and requiring participants to
integrate these representations to solve the task. The NBT fulfilled these criteria (cf.
Nuerk et al., 2002b). In an fMRI using a verification version of the NBT we aimed at
investigating the influence of processes of unit-decade integration, in this case the
impact of decade crossings on task performance (e.g., 24_28_32 vs. 20_24_28; see
Nuerk et al., 2002b).
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