Effects of concurrent arithmetical and syntactic complexity on self-paced reaction times and eye fixations.

Two dual-task experiments (replications of Experiments 1 and 2 in Fedorenko, Gibson, & Rohde, Journal of Memory and Language, 56, 246-269 2007) were conducted to determine whether syntactic and arithmetical operations share working memory resources. Subjects read object- or subject-extracted relative clause sentences phrase by phrase in a self-paced task while simultaneously adding or subtracting numbers. Experiment 2 measured eye fixations as well as self-paced reaction times. In both experiments, there were main effects of syntax and of mathematical operation on self-paced reading times, but no interaction of the two. In the Experiment 2 eye-tracking results, there were main effects of syntax on first-pass reading time and total reading time and an interaction between syntax and math in total reading time on the noun phrase within the relative clause. The findings point to differences in the ways individuals process sentences under these dual-task conditions, as compared with viewing sentences during "normal" reading conditions, and do not support the view that arithmetical and syntactic integration operations share a working memory system.