The bottle and the glass say to me: 'Pour!'

The present study aimed at determining whether the observation of two functionally compatible artefacts, that is which potentially concur in achieving a specific function, automatically activates a motor programme of interaction between the two objects. To this purpose, an interference paradigm was used during which an artefact (a bottle filled with orange juice), target of a reaching-grasping and lifting sequence, was presented alone or with a non-target object (distractor) of the same or different semantic category and functionally compatible or not. In experiment 1, the bottle was presented alone or with an artefact (a sphere), or a natural (an apple) distractor. In experiment 2, the bottle was presented with either the apple or a glass (an artefact) filled with orange juice, whereas in experiment 3, either an empty or a filled glass was presented. In the control experiment 4, we compared the kinematics of reaching-grasping and pouring with those of reaching-grasping and lifting. The kinematics of reach, grasp and lift was affected by distractor presentation. However, no difference was observed between two distractors that belonged to different semantic categories. In contrast, the presence of the empty rather filled glass affected the kinematics of the actual grasp. This suggests that an actually functional compatibility between target (the bottle) and distractor (the empty glass) was necessary to activate automatically a programme of interaction (i.e. pouring) between the two artefacts. This programme affected the programme actually executed (i.e. lifting). The results of the present study indicate that, in addition to affordances related to intrinsic object properties, "working affordances" related to a specific use of an artefact with another object can be activated on the basis of functional compatibility.