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

numbers is assumed to be more precise and solid (Dehaene, 2001). The angular gyrus is
expected to be activated more strongly for triplets with a small problem size. In contrast,
when number magnitude increases, deeper magnitude processing is required and thus
increased activation in the intraparietal cortex is expected.
Decade crossing: Decade crossing reflects the interaction between magnitude
processing and the structure of the symbolic base-10 Arabic system (Wood et al., 2006).
When there is no decade crossing, no such symbolic transformations need to be performed,
thus activation in the intraparietal cortex should less pronounced. Similar to small bisection
ranges an increase in fMRI signal in the left angular gyrus is expected, as familiarity is
enhanced when all three numbers of a triplet are from the same decade and, actually, only the
unit digits of the triplet have to be bisected.
Distance to the mean: Triplets with a small distance to the correct mean of the interval
should lead to increased activation in the intraparietal cortex compared to triplets with a large
distance to the mean. This may be attributed to more fine-grained magnitude processing
required to differentiate the central number of the interval from its correct mean when these
are numerically close to each other.
Multiplicativity: Multiplicatively related triplets should activate the left angular gyrus
more strongly than triplets that are not part of a multiplication table indicating retrieval
processes for well-learned arithmetic problems (Delazer et al. 2004, Cohen et al., 2000). In
contrast, for multiplicatively unrelated triplets, more intense magnitude processing and
manipulation is required. Therefore, activation in prefrontal and intraparietal regions should
be increased (cf. Delazer et al., 2004).
Bisection possibility: Finally, evaluating bisection possibility might reflect a cognitive
set change. When the interval cannot be bisected by an integer, the central (integer) number
cannot be the correct response. Therefore, in these triplets all subsequent magnitude
manipulations should be discontinued. It is expected that brain activation for triplets
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