Cold objects pop out!

Abstract

We can haptically extract thermal properties of different material, but we can also sense object temperature. It has been shown that thermal properties of materials are not very salient features. In this study, we investigate saliency of actual temperature differences. To this end we let subjects grasp varying numbers of spheres in the hand. These spheres were warmer (38°C) than the hand temperature, but in half of the trials there was one sphere colder (22°C) than the hand temperature. Subjects had to indicate whether the cold sphere was present and response times were measured as a function of the number of spheres. This yielded a target present slope as small as 32 ms/item. This is comparable to slopes found earlier for search for a tetrahedron among spheres and indicates that there is pop-out effect for a cold sphere among warm spheres.