Figure 1. Schematic of the experimental set up and stimulus presentation.

(A) The set up was positioned 50 cm from the focal individual. In the stream the lower box (1) serves as anchor for the upper set-up and a loudspeaker (2) connected to an portable player (3). A string (4) operated by the experimenter inserted through the upper box (5) stretched the artificial leg behind a model frog (6). A rubber band (7) automatically pulled back the leg and the attached foot (8). (B) After a 60 s baseline of no response the stimuli (S; acoustic, visual and multimodal) were presented for 30 s followed by a 90 s control period. Stimuli conditions were counterbalanced between positions S1, S2 and S3.