Girelli, Luisa; (1998) Accessing number meaning in adults and children. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis aims to clarify different aspects of the mechanisms underlying number processing. In particular, the research has two main purposes; first, to explore the conditions under which numerals may autonomously access semantics; second, to investigate whether transcoding from one number format to another can be accomplished bypassing the semantic system. These theoretical issues were addressed in two series of experimental studies and in a single-case study. In the first series of experiments, a number-Stroop paradigm was used to explore similarities and differences between intentional and unintentional processing of numerical information with the specific purpose of tracing the developmental changes in the autonomous processing of Arabic numerals. Pre-schoolers, primary-school children of different ages and university students compared either numerical size or physical size of Arabic numerals varying along both dimensions. Task- and age-related differences in the size-congruity effect strongly suggest that the autonomous processing of numerical information arises gradually as numerical skills progress. In the second series of experiments, the hypotheses of a modality-independent automatic access to magnitude representation and of an asemantic mapping between Arabic and verbal numerals were investigated by means of two matching tasks differing in the level of processing required. The results challenge the assumption of a completely autonomous semantic access to magnitude information and suggest that this phenomenon is modulated by both stimuli selection and task demands. Finally, a neuropsychological single-case study relevant to the addressed issues is reported. The study investigates the effect of different notations and the effect of different tasks on the production of verbal numerals in a phonological dyslexic patient. The results are consistent with the assumption of semantic and asemantic pathways in number transcoding and point to the importance of a more refined distinction between different type of number meanings. The results are critically evaluated and possible implications for future research are discussed.

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