Figure 1. Materials and methods.

(a) Experimental set-up. Our system performed feedback control to the surface temperature. It could also selectively project colours onto the hand that was in contact with the surface. (b) Experimental conditions. In Experiment 1, the colour was manipulated by attaching blue or red colour paper onto the thermal display. In Experiment 2, the colour was manipulated by projecting blue or red colour onto the hand. In both experiments, an eyes-closed control condition was included.