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

second summand but not on the first summand [r = .68, p < .001, n = 48; r = - .22, p = .13, n =
48, respectively].
Executing the carry – rule-based updating of the decade digit of the result
Moeller and colleagues (2009b) proposed a two-stage processing model of eye
fixation behaviour for numerical tasks. In an initial bottom-up processing stage (indicated by
influences on gaze duration) the constituting digits of the first number may be identified
largely automatic and assigned their stimulus-driven lexical values (e.g., place-value position)
by extracting their physical features and activating the memorized visual number forms (cf.
Henik & Tzelgov, 1982; Moeller et al., 2009b). After integrating the constituting digits of a
number into the place-value structure of the Arabic number system, the magnitude of the
number may be accessed. The second processing stage reflecting a subsequent top-down
driven wrap-up stage is supposed to be initiated after all the numbers of the actual problem
have been encoded. At this stage, the numbers of an arithmetical problem may be integrated
and put into relation with the other numbers by checking top-down mediated plausibility
and/or processing rules using the lexical attributes of the single numbers. This process is
supposed to be reflected by eye-movement measures capturing rather late processing such as
total reading time. Based on their model of eye fixation behaviour in numerical tasks Moeller
and colleagues (2009b) predicted longer total reading times on the decade digit of the result in
carry addition problems than in non-carry problems. The authors suggested that calculating
the sum of the decade digits and, in particular, updating this sum by the carry in carry addition
problems (e.g., 25 + 39 = 64, units: 5 + 9 = 14; tens: 2 + 3 + 1 = 6) represents the
application/execution of a specific processing rule. This should be reflected in eye movement
measures associated with rather late top-down processing such as the total reading time on a
given interest area.
79