DEVELOPMENT OF DIMENSIONAL VS GLOBAL PROCESSING IN HAPTICS - THE PERCEPTUAL AND DECISIONAL DETERMINANTS OF CLASSIFICATION SKILLS

Development of dimensional vs. global modes of processing in hapatics was examined in children (aged 5 and 9) and adults with stimuli varying along their texture density and hardness dimensions. In Expt 1 subjects were presented with a free classification task. Task 1 compared overall similarity classification (in which the grouped stimuli were similar on both dimensions) to part-identity classification (in which the grouped stimuli were identical on one dimension and and very different on the other). Prominent part-identity responses were observed at age 9 but not at age 5 and in adults. Task 2 compared overall similarity to part-similarity classification (in which the grouped stimuli were similar on one dimension and very different on the other). Prominent overall similarity responses were observed in all age groups, demonstrating that subjects processed the stimuli across both dimensions. Experiment 2 (adapted from Garner, 1974) was based on a constrained speeded sorting task using control (unidimensional), correlated and orthogonal bidimensional conditions. It showed that, at age 5, selective attention to the isolated dimensions of the objects was difficult since response times (RT) were lower in the control than in the orthogonal conditions. These results were discussed in relation to the characteristics of haptic exploration and to the perceptual vs. decisional components involved in these classification tasks.