The Integration and Dissociation of Thermal and Frictional Cues During Material Identification

This study investigated the effects of thermal and frictional cues during a forced-choice material identification task. Thermal properties of the three materials presented (pine, Lexan, aluminum) were conveyed using either real materials or a temperature-controlled aluminum pad to simulate real material effusivities. Friction either varied for the real materials presented, or was constant when the temperature-controlled aluminum simulation pad was presented. Experiments 1 and 2 employed natural materials, while experiments 3 and 4 involved thermal simulations. Thermal cues alone were allowed in experiments 1 and 3 by allowing participants only static exploration with the index finger, with cutaneous contact only in the normal direction. In Experiments 2 and 4, there was dynamic exploration by lateral stroking of the index finger, allowing both thermal and friction cues to be transmitted. Dependent measures included a judgment of the material that was explored, as well as contact forces. The simulation of material effusivity was shown to be valid as participants had identification accuracies that were similar to real materials during static exploration. Material identification accuracy was higher when congruent cues were presented and was lower when incongruent cues were presented. Peak normal force was higher during static exploration, compared to dynamic. These results were interpreted in terms of a framework of single modality competition and cooperation.