DIMENSIONAL AND OVERALL SIMILARITY CLASSIFICATIONS IN HAPTICS - A DEVELOPMENTAL-STUDY

The developmental change from global towards dimensional classifications, usually observed in vision, was investigated in haptics with stimuli varying according to their size and roughness. Children aged 5 and 9 years old and adults were presented with a free classification task allowing either an overall similarity sorting or a dimensional sorting. In two experiments, the discriminability of the stimuli along one or both dimensions was varied. Results showed that although more overall similarity classifications were observed in children than in adults, this kind of classification was never dominant (i.e., it was never chosen more frequently than would be predicted by chance). In addition to these developmental effects, effects due to the magnitude of stimulus difference were observed: A stimulus tended to be matched with the standard especially if it was slightly different from it or if the other comparison objects were much more different from this standard. This appeared in the first experiment testing dimensional versus overall similarity matching, and in the second experiment testing dimensional size versus dimensional roughness matching. These results were discussed with reference to the characteristics of haptic exploratory procedures.