Haptic search for movable parts

Abstract

How do we know that we are touching 1 single object instead of 2 different ones? An important cue is movability: When different sources of input can move independently, it is likely that they belong to different objects or that the object consists of movable parts. We hypothesize that the haptic feature "movability" is used for making this differentiation and we expect movability to be detected efficiently. We investigated this hypothesis by using a haptic search task. In Experiment 1, participants were asked to press down on piano-like keys and respond whether 1 key was movable while the rest were static or the other way around (detection only). Search strategy was determined by comparing performance of 4 response time models. This showed that the search slope for the target absent and present trials was the same (detection without localization model). In Experiment 2, we asked participants to localize the target, in order to investigate whether localization is an extra processing step. In this case our localization after detection model described the data best. This suggests that the target was detected independent of localization. To our knowledge this is the first time such a search strategy has been reported in haptic search, and it highlights the special role of the detection of movability.