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

the middle the beneficial effect of a central number smaller than the arithmetical middle was
more pronounced than for close distances (930 ms vs. 203 ms). Finally, the three participant
groups did not differ reliably in terms of RT [F(2, 15) < 1].
Errors: In the error analysis a main effect of group was observed [F(2,15) = 6.83, p <
.01]. Bonferroni-Holm corrected t-tests showed that neglect patients committed reliably more
errors than control patients [+5.0 %, t(10) = 3.41, p < .01, one-sided] as well as healthy
controls [+5.0 %, t(10) = 3.12, p < .01, one-sided]. Additionally, the interaction of distance to
the middle and size relative to the middle was significant [F(1, 15) = 5.23, p < 05.]. This
indicates that for triplets with a central number numerically close to the arithmetical middle
rejection was more error prone when than when the central number was smaller than the
middle compared to when it was larger than the middle (6.4 % vs. 3.9 % errors, respectively).
However, this pattern was reversed for triplets with a central number far from the middle
(smaller: 1.9 % vs. larger: 6.1 %). There were no further significant main effects of the
manipulated item characteristics [all F < 1.16, all p > .30 or interactions of group with any of
them [all F < 1.11, all p > 13].
Bisected triplets (RT and error data):
Decade crossing: In line with the hypothesis, the interaction of decade crossing and
participant group was reliable for errors [F(2, 15) = 6.53, p < .01], but not for response
latencies [F(2, 15) < 1]. Bonferroni-Holm corrected t-tests were conducted to directly test the
hypothesis of neglect patients’ performance being impaired most for triplets crossing into the
next decade. Therefore, the absolute effects of decade crossing were contrasted for neglect
patients vs. patient controls [t(10) = 0.90, p = .20, one-sided] as well as for neglect patients vs.
healthy controls [t(10) = 2.82, p < .05, one-sided b ]. This indicates that the increase of errors
b Note: Again, similar results were obtained when directly contrasting the effects of decade crossing in an oneway
ANOVA with subsequent post-hoc Dunnett t-tests: neglect vs. patient control p = .37, neglect vs. healthy
control p < .01.
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