Stimulus and procedure
Participants stood in front of the large screen and were free to move as they wished. The display consisted of four virtual items: a black target (2 cm diameter disc), a grey hitting zone (10 × 3 cm horizontal rectangle, presented 15 cm above screen centre) and two red items (5 cm diameter discs), separated by a gap.At the beginning of each trial, a green starting point (2 cm diameter disc) was presented 35 cm below the centre of the hitting zone. The gap between the red items was 5 cm wide and its centre was 5 cm below the centre of the hitting zone. To start a trial, participants placed the index finger of their dominant hand on the starting point. Between 500 and 700 ms after they did so, the starting point disappeared, and the black target appeared 10 cm to the left of the centre of the hitting zone, moving rightward at 20 cm/s. Exactly 300 ms after the target appeared, it jumped either leftward or rightward by 1 cm. We picked this time because it allowed participants to initiate their movement towards the target before the jump, but not be so close to the red items that they did not have time to respond. Figure Position of the hand at the time of the target jump (empty circles) and 100 ms later (filled circles). Each circle shows the average position of the hand for an individual participant. Different colours indicate the three groups of participants. The left panel shows the position of the hand when the gap size changed at the time of the target appearance (i.e. early); the right panel shows the position of the hand when the gap size changed at the time of the target jump (i.e. late)On arrival, participants read written instructions. These instructions were then repeated verbally to ensure understanding. Specifically, participants were instructed to slide their finger through the target whilst it was within the hitting zone. Participants in the obstacles group were told to avoid the red items, whereas participants in the irrelevant item group were told that the red items were irrelevant to the task. At that moment, participants were not aware that there were different groups who received different instructions. All participants were told that every time they successfully followed the instruction, they would receive 