Top-down modulation of shape and roughness discrimination in active touch by covert attention

Due to limitations in perceptual processing, information relevant to momentary task goals is selected from the vast amount of available sensory information by top-down mechanisms (e.g. attention) that can increase perceptual performance. We investigated how covert attention affects perception of 3D objects in active touch. In our experiment, participants simultaneously explored the shape and roughness of two objects in sequence, and were told afterwards to compare the two objects with regard to one of the two features. To direct the focus of covert attention to the different features we manipulated the expectation of a shape or roughness judgment by varying the frequency of trials for each task (20%, 50%, 80%), then we measured discrimination thresholds. We found higher discrimination thresholds for both shape and roughness perception when the task was unexpected, compared to the conditions in which the task was expected (or both tasks were expected equally). Our results suggest that active touch perception is modulated by expectations about the task. This implies that despite fundamental differences, active and passive touch are affected by feature selective covert attention in a similar way.

There are zip files for the main experiment and the two pilot experiments, which contain all data relative to the publication. The data of each participant is contained in a separate folder. This folder contains a *.raw file with the participant's answers for each session of the experiment and a "data" folder, which contains movement trajectories (*.trj files) for each session in separate folders.

Variables of the main experiment are described in the file VARIABLE_CODES_MainExp.txt and the variables of the pilot experiments are described in the files VARIABLE_CODES_PilotRoughness.txt and VARIABLE_CODES_PilotShape.txt.