27.12.2013 Views

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

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

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

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

unit sum has to be carried to <strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> result. Consider here for instance<br />

25 + 39: <strong>the</strong> sum <strong>of</strong> <strong>the</strong> unit digits is 5 + 9 = 14 and thus a carry is necessary to obtain<br />

<strong>the</strong> correct result. <strong>The</strong>reby, <strong>the</strong> necessity <strong>of</strong> a carry is driven by calculation processes<br />

upon <strong>the</strong> unit digits.<br />

(ii) After it has been recognized that a carry is needed <strong>the</strong> carry procedure still has to be<br />

executed properly: This means that <strong>the</strong> carry, i.e., <strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> unit sum, has<br />

to be added to <strong>the</strong> sum <strong>of</strong> <strong>the</strong> decade digits <strong>of</strong> <strong>the</strong> summands. In above mentioned<br />

example, <strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> unit sum is 1 (from 14). Adding this to <strong>the</strong> sum <strong>of</strong> <strong>the</strong><br />

decade digits <strong>of</strong> <strong>the</strong> summands, i.e., 2 + 3 + 1 = 6 (italics indicating carry) results in<br />

<strong>the</strong> decade digit <strong>of</strong> <strong>the</strong> correct result (25 + 39 = 64).<br />

<strong>The</strong> carry effect in addition has mainly been investigated by reaction time experiments<br />

(Deschuyteneer et al., 2005; Fürst & Hitch, 2000; Klein et al., submitted) as well as functional<br />

Magnetic Resonance Imaging (fMRI) studies (Kong et al., 2005). However, to investigate <strong>the</strong><br />

nature and sequence <strong>of</strong> <strong>the</strong> basic cognitive processes underlying <strong>the</strong> carry effect in addition a<br />

more fine-grained analysis by a supplemental evaluation <strong>of</strong> participants’ eye fixation<br />

behaviour may be informative since eye fixations are an established indicator <strong>of</strong> what is being<br />

processed at <strong>the</strong> moment (e.g., Rayner & Pollatsek, 1989). Applied to an addition problem<br />

this means that identifying which digit is fixated at a time also indicates which digit is<br />

actually processed.<br />

In <strong>the</strong> current study, we applied this assumption to an addition verification task and<br />

derived specific hypo<strong>the</strong>ses for <strong>the</strong> <strong>influence</strong> <strong>of</strong> underlying cognitive processes on <strong>the</strong> eye<br />

fixation behaviour in addition problems with and without carry. First, <strong>the</strong> validity <strong>of</strong> eye<br />

movement data can be studied for this effect. Eye movement research has shown that<br />

increasing task difficulty is resolved by ei<strong>the</strong>r more fixations and/or longer total reading times<br />

65

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!