Figure 1.

Experimental set-up. (a) Experimental set-up and trial description. Participants sat behind a black curtain with their dominant hand inserted through the curtain and positioned comfortably on a semi-soft foam surface. A speaker was positioned as close as possible to the position at which the hand of the participant would pat either the wooden ball or a pen on the surface underneath. A touchscreen was placed just below the foam and, when pressed, the sound was played through the speaker. (b) An example of the auditory-only condition during which participants tapped a pen on the touch screen twice to hear the sound made by each ball, before judging which sound was produced by the bigger ball. (c) An example of the haptic condition during which participants patted a pair of wooden balls (one at the time) while wearing a thick glove, before judging which ball was bigger.