Abstract

In The red ball is flying through the air in front of the blue ball the red ball’s location is described in relation to a blue ball, which acquired a ‘front’ through motion direction. We for the first time investigated the relative contribution of three motion parameters (in isolation and combination) for generating front-back axes when talking about object location during motion: translational motion (co-ordinate changes of objects in space), intrinsic motion (object part motion, for example, turning car wheels), and motion control (externally imposed co-ordinate changes). 28 native English speakers indicated the acceptability of the adpositions in front of and behind, and the verbs leading and following, while watching two moving objects through a virtual reality headset. Acceptability ratings showed that axis strength decreased according to our hypotheses: translational motion combined with intrinsic motion, with agreement in direction > translational motion > translational motion combined with intrinsic motion, with conflict in direction > intrinsic motion. Also, according to predictions, the front-back axis was stronger for adpositions than verbs if motion control applied. Over and above previous studies we not only show that translational motion can generate front-back axes, but that also intrinsic motion can do that, and that the translational motion parameter needs refinement into motion due to an external force or due to self-motion. We explained a weaker axis for intrinsic motion as being due to inferencing motion direction (as in, for example, the wheels are turning right, and therefore the object must be going right), whereas axes generated during translational movement are generated directly by visual input. We also introduced a new method in calculating axis strength.