Figure 2

Experiment Overview. We conducted three behavioural experiments to examine the role of feedback. (A) In Experiment 1 we allowed subjects to use visual feedback throughout, and alternated the presence of vibrotactile feedback. Object weight (lightweight, 'L', and heavy, 'H') varied between blocks as shown. The order of presentation of feedback was counterbalanced (indicated by the double-headed arrow). (B) In Experiment 2 we used two groups of subjects, one with vibrotactile feedback and one without. Subjects performed two blocks with visual feedback, and a third immersed in darkness, with different object weights. (C) In Experiment 3 subjects had an initial training phase, then had two phases of trials in all four feedback configurations (visual, tactile, neither and both), counterbalanced as shown.