Perceiving affordances in rugby union.

To succeed in competitive environments, players need to continuously adjust their decisions and actions to the behaviour of relevant others. Players' interactions demand ongoing decisions that are constrained by what is previously defined (e.g., coaches' prescriptions that establish 'what' to do) and by information that is available in the context and specifies not only 'what' the player should do, but also 'how', 'when' and 'where'. We describe what affordances emerge to the ball carrier as a consequence of changes in kinematic variables, such as interpersonal distances or distances to the nearest sideline. Changes in these variables determine whether and when different actions are possible. The ball carrier tended to perform a pass when the tackler was farthest from the sideline and the velocity of approach to the tackler did not seem to effect the ball carrier's decision. In the few episodes where the ball carrier moved forward instead of passing the ball, he was mainly influenced by contextual information, such as the variability of the players' distance to the nearest sideline. In sum, actors must be aware of the affordances of others that are specified by particular variables that become available just before decision-making.